Author Archives: teel9174

Magnetic Card Reader (TTL) with Arduino – Part II

<- Part 1

Introduction

In the first part, I did some troubleshooting to fix an issue with the particular card readers that I have on hand. In part two, I will go over some code changes which allow the card reader to work without needing to add a capacitor to the data line and allowing the Arduino Nano to support two card readers.

I submitted an issue/comment to the magstripelib library in GitHub and was promptly received replies from Yoan Tournade and Carlos Rodrigues. Yoan suggested using INPUT_PULLUP on the interrupt pins may help. I modified the call to pinMode to use INPUT_PULLUP rather than INPUT but it made no difference. I suspect that there would be no difference as the card reader is pulling the pin up to the +5V rail so it is unnecessary to do in internal to the Arduino. It was worth a shot and I appreciated the suggestion.

Carlos commented that it is best to use an interrupt on the data pin as it reduces the amount of time spent in the clock interrupt handler.  This is true but the I decided to rewrite the code to read the data pin inside the clock interrupt to solve two problems for my particular instance.

  • Eliminate the need for the capacitor on the data line
  • Allow an Uno or Nano to be able to read two card readers

I had planned to fork Carlos’s original code and make some changes to have him pull back in if he felt they added to the magstripelib but felt that the changes that I wanted to make serve a different goal from Carlos’s code. The changes that I made are for a very small audience of users if any at all so I chose to simply include modified header and class files into the Arduino project.

On to the Code

The following code is available on GitHub at https://github.com/richteel/MagCardReader.

Allowing the Arduino Nano to read two card readers was the real motivation for making the changes to the code. It did present a challenge that I had not anticipated. I had to figure out how to use the same interrupt code to read from a different data pin depending on this pin which fired the interrupt.

I wanted to be able to support 2 card readers on one Arduino Nano as the card readers that I have can be setup to read track 1 or track 2. The cover holding the reader head may be removed. The cover contains two sets of notches which allow the head to be in one of two positions. Since I have two readers, I configured one for track 1 and the other for track 2.

Below is a list of some of the code changes made from the magstripelib.

  • Change class name from MagStripe to MagCardRead
  • Added volatile variable to hold the current data pin number
  • Modified the constructor to allow the assigning of the card detect, strobe (aka clock), and data pins for the reader
  • Removed the data interrupt handler
  • Read the data pin in the strobe interrupt handler

MagCardRead.h

/*
   MagCardRead - Read data from a magnetic stripe card.

   Copyright (c) 2020 Richard Teel <richteel@teelsys.com>

   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   THE SOFTWARE.


   Modified from Carlos Rodrigues <cefrodrigues@gmail.com> original MagStripe library
   Based on this: http://cal.freeshell.org/2009/11/magnetic-stripe-reader/
     ...and this: http://www.abacus21.com/Magnetic-Strip-Encoding-1586.html
*/

#ifndef MAGCARDREAD_H
#define MAGCARDREAD_H

#include 

// Default pins used by init
// The data and strobe pins depend on the board model...
#if defined(__AVR_ATmega32U4__)
// Arduino Leonardo and Arduino Micro:
#  define MAGSTRIPE_RDT 3  /* data pin (yellow) */
#  define MAGSTRIPE_RCL 2  /* strobe pin (orange) */
#else
// Arduino Uno and Arduino Mega:
#  define MAGSTRIPE_RDT 2  /* data pin (yellow) */
#  define MAGSTRIPE_RCL 3  /* strobe pin (orange) */
#endif

#  define MAGSTRIPE_CLS 4  /* card present pin (green) */

// Cards can be read in one of these possible ways...
enum ReadDirection { READ_UNKNOWN, READ_FORWARD, READ_BACKWARD };

class MagCardRead {
  public:
    MagCardRead(uint8_t cardDetectPin = MAGSTRIPE_CLS, uint8_t strobePin = MAGSTRIPE_RCL, uint8_t dataPin = MAGSTRIPE_RDT);

    // Initialize the library (attach interrupts)...
    void begin(uint8_t track);

    // Deinitialize the library (detach interrupts)...
    void stop();

    // Check if there is a card present for reading...
    bool available();

    // Read the data from the card as ASCII...
    short read(char *data, uint8_t size);

    // The direction of the last card read...
    enum ReadDirection read_direction();

  private:
    uint8_t _cardDetect_pin;
    uint8_t _strobe_pin;
    uint8_t _data_pin;

    uint8_t _track;
    enum ReadDirection direction;

    void reverse_bits();
    bool verify_parity(uint8_t c);
    bool verify_lrc(short start, short length);
    short find_sentinel(uint8_t pattern);
    short decode_bits(char *data, uint8_t size);
};


#endif  /* MAGCARDREAD_H */


/* vim: set expandtab ts=4 sw=4: */

MagCardRead.cpp

/*
   MagCardRead - Read data from a magnetic stripe card.

   Copyright (c) 2020 Richard Teel <richteel@teelsys.com>

   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   THE SOFTWARE.


   Modified from Carlos Rodrigues <cefrodrigues@gmail.com> original MagStripe library
   Based on this: http://cal.freeshell.org/2009/11/magnetic-stripe-reader/
     ...and this: http://www.abacus21.com/Magnetic-Strip-Encoding-1586.html
*/

#include "MagCardRead.h"

#include 

// Enough bits to read any of the three tracks...
#define BIT_BUFFER_LEN 800


// Variables used by the interrupt handlers...
static volatile bool next_bit = 0;                       // next bit to read
static volatile unsigned char bits[BIT_BUFFER_LEN / 8];  // buffer for bits being read
static volatile short num_bits = 0;                      // number of bits already read
static volatile uint8_t vdata_pin = 0;                   // data pin to be read by interrupt


// Manipulate the bit buffer...
static void bits_set(short index, bool bit);
static bool bits_get(short index);

// The interrupt handlers...
static void handle_strobe(void);

MagCardRead::MagCardRead(uint8_t cardDetectPin, uint8_t strobePin, uint8_t dataPin)
{
  _cardDetect_pin = cardDetectPin;
  _strobe_pin = strobePin;
  _data_pin = dataPin;

  direction = READ_UNKNOWN;
}

void MagCardRead::begin(uint8_t track)
{
  _track = track;

  pinMode(_cardDetect_pin, INPUT_PULLUP);
  pinMode(_strobe_pin, INPUT_PULLUP);
  pinMode(_data_pin, INPUT_PULLUP);

  // Reading is more reliable when using interrupts...
  attachInterrupt(digitalPinToInterrupt(_strobe_pin), handle_strobe, FALLING);  // strobe pin
}


void MagCardRead::stop()
{
  detachInterrupt(digitalPinToInterrupt(_strobe_pin));
}


bool MagCardRead::available()
{
  vdata_pin = _data_pin;
  return digitalRead(_cardDetect_pin) == LOW;
}


short MagCardRead::read(char *data, unsigned char size)
{
  // Fail if no card present...
  if (!available()) {
    return -1;
  }

  // Empty the bit buffer...
  num_bits = 0;
  next_bit = 0;

  // Wait while the data is being read by the interrupt routines...
  while (available()) {}

  // Decode the raw bits...
  short chars = decode_bits(data, size);
  direction = READ_FORWARD;

  // If the data looks bad, reverse and try again...
  if (chars < 0) {
    reverse_bits();
    chars = decode_bits(data, size);
    direction = READ_BACKWARD;
  }

  // The card could not be read successfully...
  if (chars < 0) {
    direction = READ_UNKNOWN;
  }

  return chars;
}


enum ReadDirection MagCardRead::read_direction()
{
  return direction;
}


void MagCardRead::reverse_bits()
{
  for (short i = 0; i < num_bits / 2; i++) {
    bool b = bits_get(i);

    bits_set(i, bits_get(num_bits - i - 1));
    bits_set(num_bits - i - 1, b);
  }
}


bool MagCardRead::verify_parity(unsigned char c)
{
  unsigned char parity = 0;

  for (unsigned char i = 0; i < 8; i++) { parity += (c >> i) & 1;
  }

  // The parity must be odd...
  return parity % 2 != 0;
}


bool MagCardRead::verify_lrc(short start, short length)
{
  unsigned char parity_bit = (_track == 1 ? 7 : 5);

  // Count the number of ones per column (ignoring parity bits)...
  for (short i = 0; i < (parity_bit - 1); i++) {
    short parity = 0;

    for (short j = i; j < length; j += parity_bit) {
      parity += bits_get(start + j);
    }

    // Even parity is what we want...
    if (parity % 2 != 0) {
      return false;
    }
  }

  return true;
}


short MagCardRead::find_sentinel(unsigned char pattern)
{
  unsigned char bit_accum = 0;
  unsigned char bit_length = (_track == 1 ? 7 : 5);

  for (short i = 0; i < num_bits; i++) { bit_accum >>= 1;                               // rotate the bits to the right...
    bit_accum |= bits_get(i) << (bit_length - 1);  // ...and add the current bit

    // Stop when the start sentinel pattern is found...
    if (bit_accum == pattern) {
      return i - (bit_length - 1);
    }
  }

  // No start sentinel was found...
  return -1;
}


short MagCardRead::decode_bits(char *data, unsigned char size) {
  short bit_count = 0;
  unsigned char chars = 0;
  unsigned char bit_accum = 0;
  unsigned char bit_length = (_track == 1 ? 7 : 5);

  short bit_start = find_sentinel(_track == 1 ? 0x45 : 0x0b);
  if (bit_start < 0) {  // error, start sentinel not found
    return -1;
  }

  for (short i = bit_start; i < num_bits; i++) { bit_accum >>= 1;                                 // rotate the bits to the right...
    bit_accum |= (bits_get(i) << (bit_length - 1)); // ...and add the current bit bit_count++; if (bit_count % bit_length == 0) { if (chars >= size) {  // error, the buffer is too small
        return -1;
      }

      // A null means we reached the end of the data...
      if (bit_accum == 0) {
        break;
      }

      // The parity must be odd...
      if (!verify_parity(bit_accum)) {
        return -1;
      }

      // Remove the parity bit...
      bit_accum &= ~(1 << (bit_length - 1));

      // Convert the character to ASCII...
      data[chars] = bit_accum + (_track == 1 ? 0x20 : 0x30);
      chars++;

      // Reset...
      bit_accum = 0;
    }
  }

  // Turn the data into a null-terminated string...
  data[chars] = '\0';

  if (data[chars - 2] != '?') {  // error, the end sentinel is not in the right place
    return -1;
  }

  // Verify the LRC (even parity across columns)...
  if (!verify_lrc(bit_start, chars * bit_length)) {
    return -1;
  }

  return chars;
}


static void bits_set(short index, bool bit)
{
  volatile unsigned char *b = &bits[index / 8];
  unsigned char m = 1 << (index % 8);

  *b = bit ? (*b | m) : (*b & ~m);
}


static bool bits_get(short index)
{
  return bits[index / 8] & (1 << (index % 8)); } static void handle_strobe() { // Avoid a crash in case there are too many bits (garbage)... if (num_bits >= BIT_BUFFER_LEN) {
    return;
  }

  next_bit = !digitalRead(vdata_pin);

  bits_set(num_bits, next_bit);
  num_bits++;
}


/* vim: set expandtab ts=4 sw=4: */

MagCardReader.ino

/*
   MagCardRead - Read data from a magnetic stripe card.

   Copyright (c) 2020 Richard Teel <richteel@teelsys.com>

   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   THE SOFTWARE.


   Modified from Carlos Rodrigues <cefrodrigues@gmail.com> original MagStripe library
   Based on this: http://cal.freeshell.org/2009/11/magnetic-stripe-reader/
     ...and this: http://www.abacus21.com/Magnetic-Strip-Encoding-1586.html
*/

#include "MagCardRead.h"


#define pinCardDetect1 4
#define pinStrobe1 2
#define pinData1 5

#define pinCardDetect2 6
#define pinStrobe2 3
#define pinData2 7

// Visual feedback when the card is being read...
static const byte READ_LED = 8;  //13
static const byte ERROR_LED = 9; //12

//MagCardRead card;
//MagCardRead card(pinCardDetect);
MagCardRead card(pinCardDetect1, pinStrobe1, pinData1);
MagCardRead card2(pinCardDetect2, pinStrobe2, pinData2);

/*
   Track 3 is the one that can contain the most characters (107).
   We add one more to accomodate the final '\0', as the data is a C string...
*/
static const byte DATA_BUFFER_LEN = 108;
static char data[DATA_BUFFER_LEN];


void readCard(MagCardRead crd) {
  // Don't do anything if there isn't a card present...
  if (!crd.available()) {
    return;
  }

  // Show that a card is being read...
  digitalWrite(READ_LED, HIGH);
  Serial.println("-- Read Completed --");

  // Read the card into the buffer "data" (as a null-terminated string)...
  short chars = crd.read(data, DATA_BUFFER_LEN);

  // Show that the card has finished reading...
  digitalWrite(READ_LED, LOW);

  // If there was an error reading the card, blink the error LED...
  if (chars < 0) {
    digitalWrite(ERROR_LED, HIGH);
    delay(250);
    digitalWrite(ERROR_LED, LOW);
    Serial.println("Read Error...");
    Serial.println(chars);

    return;
  }

  Serial.println("Good Read...");
  Serial.print("Read Direction: ");
  //Serial.println(crd.read_direction());
  Serial.println(crd.read_direction() == 1 ? "Forward" : crd.read_direction() == 2 ? "Backward" : "Unknown");


  // Send the data to the computer...
  Serial.println(data);
}

void setup()
{
  pinMode(READ_LED, OUTPUT);
  pinMode(ERROR_LED, OUTPUT);

  // The card data will be sent over serial...
  Serial.begin(9600);

  // Initialize the library for reading track 2...
  card.begin(1);
  card2.begin(2);

  // Start with the feedback LEDs off...
  digitalWrite(READ_LED, LOW);
  digitalWrite(ERROR_LED, LOW);
}


void loop()
{
  readCard(card);
  readCard(card2);
}


/* EOF - MagCardRead.ino */

Conclusion

Most applications with card readers and Arduinos should make use of the magstripelib library by Carlos Rodrigues. If you have a project that uses one of the card readers mentioned in the original blog post then add a capacitor to the data line as mentioned in the original post. If for some reason, you cannot add a capacitor as mentioned or you need to read from two readers, then the code mentioned here may be a good solution.

Learning Android Development using Big Nerd Ranch’s book

I have been contemplating learning Android development for a while now. I have dabbled in it in the past but never took a deep dive to create an application from scratch. I decided to go through a book from start to finish to see if that will give me what I need to finally take the dive.

Android Programming Book by Big Nerd Ranch

Link to the book on Amazon

The book is laid out really well and explains things much clearer than other books I have looked at over the years. I will say that Java development is still not much better than it was 20 years ago, at least on a Windows OS. I know some people will like to bash me for that comment but let me tell you about day one of working through the book and why Java still has a long way to go. (In retrospect after writing this, the blame is not really Java but the IDE. About 20 years ago, both were an issue but at least my issue is more to do with the IDE rather than Java.)

Installation of Android Studio seemed to go well. I got through the GeoQuiz example with no problems other than needing to use a physical device rather than the emulator due to Hyper-V being enabled on my system. I then worked on the challenge by copying the completed example and opening the copy. I made my changes and attempted to launch the application. I received an error that the apk could not be loaded or copied and a prompt was given to uninstall the apk with a warning that user data may be deleted. Since the application did not have associated user data, I clicked the button to uninstall the apk. Another error showed up in the log stating that the apk could not be copied or installation failed. (Sorry, I do not call the exact text.)

At this point, I assumed that the issue was with my device having the application installed from the sample so I decided to try the emulator. I was being a bit lazy so I clicked the link in the emulator selection to turn off Hyper-V. This change required a reboot so I let the PC reboot. On reboot, Windows 10 attempted to fix an error and stated that automatic repair failed to fix the issue. I attempted to turn Hyper-V back on from the command prompt but I was unable to do so from the Windows PE command prompt. I then decided to try turning off early anti-virus and the PC rebooted. Of course I was not happy about that especially since my AV software kept complaining that it could not reach the live-update site and other issues. Basically I had a mess to clean up. Once I finally got the OS squared away, I decided to go back to the challenge. Now Android Studio was having all kinds of issues. (All of these issues may be related to other attempts to boot back into Windows including restoring a previous restore point.)

I uninstalled Android Studio, deleted the files in the Program Files folder, rebooted, and reinstalled Android Studio. I was still having issues launching Android Studio. I finally found that I needed to delete the contents of the C:\Users\AppData\Local\Android\Sdk folder. I then needed to reinstall the SDK, emulator, and build tools. Once these were reinstalled, Android Studio behaved well as it did before. I attempted to run the application and the emulator launched so that was great news but I received the original error regarding the apk file.

I was at a loss but looked a bit more into the log file and it pointed me to a file in the C:\Users\Documents\AndroidStudioProjects\GeoQuiz – Challenge\app\build\intermediates\split-apk\debug\slices folder. I deleted all of the files in the folder but I still received the same message. This was getting quite frustrating so I decided to try deleting all of the files and folders in the C:\Users\Documents\AndroidStudioProjects\GeoQuiz – Challenge\app\build folder. I attempted to build and run the application again. Low and behold, this time the application launched in the emulator. Finally success.

With all of this said, I’m going to keep marching on. It is very frustrating to have the Android Studio behave this way but hopefully my rant here will help someone. If nothing else, it will serve as a reminder to myself what to do when this error occurs.

Here are some locations of note regarding where Android Studio places files. If you want to uninstall and reinstall Android Studio, you should uninstall, delete the following folders, and reinstall. (These may not be all of the locations but these are the ones I found.)

  • C:\Program Files\Android
  • C:\Program Files (x86)\Android
  • C:\Users\.android
  • C:\Users\.AndroidStudio3.1
  • C:\Users\.gradle
  • C:\Users\AppData\Local\Android

Pipboy 3000

OVERVIEW

My daughter wanted to cosplay as a character from Fallout 3 for Awesomecon 2018 in Washington D.C. We found Noe and Pedro Ruiz’s design on learn.adafruit.com 1 and decided to build it. She decided do this cosplay a few days before the event so it was going to be a challenge to complete it in time but we did it.

I thought getting the electronics in time was going to be the biggest challenge but the biggest challenge was reducing the time for the 3D prints. We started on Sunday and did not finish until Wednesday afternoon. (We did not print continuously so the overall print time was less but not by much.) Noe and Pedro have some tips on reducing print time and they worked in combination with tweaking the infill and layer height.

3D PRINTING

My 3D printer is the XYZprinting daVinci 1.0. The printer is a few years old now and is not the best 3D printer by far but it does a fair job. The printer only supports ABS fulfillment and XYZprinting filament cartridges. I have yet to take time to change the head to support PLA or hack the firmware so I can use other filaments. This limits me to the colors of filament that I may use in the printer. We looked for a brown or green filament to use for the Pipboy but did not find any to my daughter’s liking. We decided to print it in white and spray paint it. We found some metallic paint which seemed to work well. Additionally, we printed the screen visor in black and the LED diffuser in natural.

As a side note, I started using Simplify3D Slicing Software with the printer and it has made a world of difference with the print quality and control of the printer. The prints come out much closer to the designed measurements than the XYZprinting software could accomplish. The software gives more options than the XYZprinting software which really came in handy for this project. Noe and Pedro recommend removing some of the supports for the armband and base-main pieces. The XYZprinting software is all or nothing regarding supports but the Simplify3D software allowed me to remove some supports while leaving others in place.

HARDWARE

Noe and Pedro do a good job in the write-up but as with most build instructions, a few things are left out or are not clear. Here are a few notes that I made along the way but it is not a complete list as we were under a very restrict time constraint to get this project done. Unfortunately that means take notes and documenting issues was not a priority.

Additional Materials needed but not listed in the materials list in the overview.

  • Electronic Parts & Components
  • Tools & Supplies
    • (Optional) Hot Glue and Hot Glue Gun
    • Adhesive foam such as weatherstripping for doors and windows

Below are the connections to the 3.5″ LCD Shield that were used in our build.

PypBoy Function Pin Pin Function PypBoy
LED + 3V3 1 2 5V  
ENC A GPIO2 3 4 5V PB 1000C +
ENC B GPIO3 5 6 GND PB 1000C –
ROT 1 GPIO4 7 8 GPIO14 ENC SW
LED – GND 9 10 GPIO15  
ROT 2 GPIO17 11 12 GPIO18  
ROT 3 GPIO27 13 14 GND ROT –
ROT 4 GPIO22 15 16 GPIO23 ROT 5
  3V3 17 18 GPIO24  
  GPIO10 19 20 GND  
  GPIO9 21 22 GPIO25  
  GPIO11 23 24 GPIO8  
ENC – GND 25 26 GPIO7  

SOFTWARE

We made a few tweaks to the software but they were to change the map and display some different text on some screens and adding some missing code to change other displayed text. I plan to post those minor changes in a future post. The more major changes implemented were to get the pypboy program to launch on start and wire up the rotary encoder so we can safely shutdown the Raspberry Pi.

The shutdown code was modified from Inderpreet Singh’s code on Element14’s website2.

REFERENCES

  1. Noe and Pedro’s writeup on learn.adafruit.com: https://learn.adafruit.com/raspberry-pi-pipboy-3000
  2. Inderpreet Singh’s Shutdown Code on Element14’s site: https://www.element14.com/community/docs/DOC-78055/l/adding-a-shutdown-button-to-the-raspberry-pi-b

Arduino delay(), millis(), etc. cause execution to halt in a library

I ran into an interesting issue yesterday while rewriting some Arduino code into a library. I figure out what was the issue but I’m not sure as to why. If someone reads this and can point me to the reason why this was an issue, please comment on this post. I would appreciate it.

PROBLEM STATEMENT (Observation): Adding any timing function in my library file would halt the execution. The time functions includes delay(), delayMicroseconds(), micros(), and millis().

ROOT CAUSE: The time function was being called in the constructor of the class. If the time function was moved to another method and called separately, the time function would work.

RESOLUTION: Modified the code to create the object, then make a call to a public method of the class. I used begin() as I have seen in other classes.

Problem code demonstrating the issue

sample.ino

#include "mylib.h"

mylib myObject = mylib();

const int ledPin =  LED_BUILTIN;
unsigned long previousMillis = 0;
const long interval = 1000;

void setup() {
   pinMode(ledPin, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();
  
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    digitalWrite(ledPin, !digitalRead(13));
  }
}

mylib.h

#if defined(ARDUINO) && ARDUINO >= 100
  #include "Arduino.h"
#else
  #include "WProgram.h"
#endif

class mylib {
  public:
    // Constructors
    mylib();

  private:
    void initialize();
};

mylib.cpp

#include "mylib.h"

mylib::mylib() {
  initialize();
}

mylib::initialize() {
  delay(100);
}

Working code demonstrating the solution

sample.ino

#include "mylib.h"

mylib myObject = mylib();

const int ledPin =  LED_BUILTIN;
unsigned long previousMillis = 0;
const long interval = 1000;

void setup() {
  pinMode(ledPin, OUTPUT);
  myObject.begin();
}

void loop() {
  unsigned long currentMillis = millis();
  
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    digitalWrite(ledPin, !digitalRead(ledPin));
  }
}

mylib.h

#if defined(ARDUINO) && ARDUINO >= 100
  #include "Arduino.h"
#else
  #include "WProgram.h"
#endif

class mylib {
  public:
    // Constructors
    mylib();

    void begin();

  private:
    void initialize();
};

mylib.cpp

#include "mylib.h"

mylib::mylib() {
  
}

mylib::begin() {
  initialize();
}

mylib::initialize() {
  delay(100);
}

Glowforge

My Glowforge finally arrived this week. I pre-ordered it in October 2015 so it took a little over two years of waiting to finally get it.

I designed and printed the obligatory escutcheon for the print button. I chose to name my Glowforge Scotty in honor of James Doohan. His character was my inspiration for becoming an engineer in the first place so I felt it was fitting.


The escutcheon after being printed.


The escutcheon after removing the tape covering.

A few thoughts on the Glowforge interface.
The interface and workflow will take a bit of getting use to but I think it will be fine once I’m more familiar with it. At first I was getting frustrated as I created a PNG image to scale. When I imported it, I thought it was too small until I realized the scale is in inches not mm. Once I realized my error, I looked for an option to change it but could not find one. I attempted to find a way to scale it to the correct size but there is no option to type in the size or view the exact measurement. It is necessary to guess what size it is by looking at the ruler on the screen which is not very accurate. What I ended up doing was using the 1:1 scale printout and placing it in the Glowforge so I could attempt to scale it correctly. Once I did that, I could not figure out how to do cuts where I wanted them. I did some reading and found that an SVG is needed for cuts. I then used Inkscape to create an SVG from a modified image with only the cuts. This worked and I was able to scale it exactly. I then created another PNG file with just the engraving and uploaded both files. I still needed to scale the engraving but that was easy and not critical. Once everything looked good, I pressed the print button. The Glowforge performed the cuts but not the engraving. I then removed the cut image and clicked print again. This time the engraving was done. On my next print, I will need to see what I did wrong here so I do not make that mistake again.

Overall it was easy to use the Glowforge but I do have a few concerns. Firstly, a desktop application to prepare the print would afford a better setup experience. Secondly, it is not possible to print if your network connection is down for any reason or if Glowforge goes out of business. While it is nice to use a device this way, it does leave users vulnerable to the existence of the company and the health of the web servers.


The original PNG file I created.


A modified PNG for the cuts. This file could not be used for the cuts as PNG files may only be used for engraving. I needed to convert this file to SVG using Inkscape.


The modified PNG for the engraving.

Overall, I’m pleased with the Glowforge. I just hope that the company and the web-service run well for many years to come so I may continue to use the Glowforge.

BTW: The size of the escutcheon is 119.903 x 119.903 mm. I was not able to upload the SVG for the cuts so if you decide to use the PNG, you will need to convert it to SVG and resize it.

All Electronics LCD-101 (256×128 LCD) with Arduino

All Electronics has a rather large LCD display which will work great in a Jeopardy! like game that I am building. The display should be rather easy to use with an Arduino or Raspberry Pi but searching for Arduino or Raspberry Pi projects using the display turns up very few details. Fortunately the SED1330F datasheet is fairly well written. With some experimentation, it is possible to figure out how to get it to work. Especially helpful is table 32 in section 9.1.2. Some of the parameters need to be changed but it is a great example of how to get the display to work.

Here is a very short video of the LCD running from an Arduino UNO. The video starts with the display showing the result from the test2 function from the sample code below. I then upload the code again with the test2 function call commented out and the testDataSheetSection9 function call uncommented.

test2(511);

testDataSheetSection9();

#include 

// All Electronics LCD-101
// HG25504 with SED1330F

// LCD Pins
#define d0 14
#define d1 15
#define d2 2
#define d3 3
#define d4 4
#define d5 5
#define d6 6
#define d7 7
#define res 8
#define rd 9
#define wr 10
#define cs 11
#define a0 12

// LCD Comands
#define SYSTEM_SET  0x40
#define SLEEP_IN    0x53
#define DISP_OFF    0x58
#define DISP_ON     0x59
#define SCROLL      0x44
#define CSRFORM     0x5D
#define CGRAM_ADR   0x5C
#define CSRDIR_R    0x4C
#define CSRDIR_L    0x4D
#define CSRDIR_U    0x4E
#define CSRDIR_D    0x4F
#define HDOT_SCR    0x5A
#define OVLAY       0x5B
#define CSRW        0x46
#define CSRR        0x47
#define MWRITE      0x42
#define MREAD       0x43

// LCD Parameters
#define LCD_RES_W 256
#define LCD_RES_H 128
#define CHAR_BITS_WIDE 8  
#define CHARS_PER_LINE  32//8 bit
#define TEXT_ROWS 16

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Serial.println("Hello world");
  delay(2000);// Give reader a chance to see the output.
  
  // Set pins for output
  setDataPinsForOutput();
  pinMode(res, OUTPUT);
  pinMode(rd, OUTPUT);
  pinMode(wr, OUTPUT);
  pinMode(cs, OUTPUT);
  pinMode(a0, OUTPUT);

  lcdReset();
  lcdInit();

  testDataSheetSection9();
  //test2(511);
}

void loop() {
  // put your main code here, to run repeatedly:
}

/*** Functions ***/

void clearGraphicsLayer() {
  // Set Start at 03E8H
  lcdWriteCommand(CSRW);
  lcdWriteData(0x03);
  lcdWriteData(0xE8);

  // Write 00H (blank data) for 8000 bytes
  lcdWriteCommand(MWRITE);
  for(int i=0; i<8000; i++) {
    lcdWriteData(0x00);
  }
}

void clearTextLayer() {
  // Set Start at 0000H
  lcdWriteCommand(CSRW);
  lcdWriteData(0x00);
  lcdWriteData(0x00);

  // Write 20H (space character) for 1000 bytes
  lcdWriteCommand(MWRITE);
  for(int i=0; i<1000; i++) {
    lcdWriteData(0x20);
  }
}

void lcdInit() {
  Serial.println("Step  3");
  //  3 Initialize LCD Sequence
  lcdWriteCommand(SYSTEM_SET);  // C
  lcdWriteData(0x30);  // P1 M0, M1, M2, W/S, IV, T/L, & DR
  lcdWriteData(0x87);  // P2 FX & WF
  lcdWriteData(0x07);  // P3 FY
  lcdWriteData(0x1F);  // P4 (C/R) Address range covered by one line
  lcdWriteData(0x23);  // P5 (TC/R) Length of one line
  lcdWriteData(0x7F);  // P6 (L/F) Frame height in lines
  lcdWriteData(0x20);  // P7 (APL)
  lcdWriteData(0x00);  // P8 (APH)
}

void lcdReset() {
  digitalWrite(res, LOW);
  // Set init state for wr & cs
  digitalWrite(wr, LOW);
  digitalWrite(cs, LOW);
  delay(50);
}

void lcdWriteCommand(byte command) {
  lcdWriteCtrl(0x05);
  lcdWriteJustData(command);
  digitalWrite(wr, HIGH); // Latch Data
  //delay(10);
}

void lcdWriteCtrl(byte ctrl) {
  digitalWrite(cs, LOW);
  digitalWrite(res, HIGH);
  
  digitalWrite(a0, ctrl & 0x04);
  digitalWrite(wr, ctrl & 0x02);
  digitalWrite(rd, ctrl & 0x01);
}

void lcdWriteData(byte data) {
  lcdWriteCtrl(0x01);
  lcdWriteJustData(data);
  digitalWrite(wr, HIGH); // Latch Data
  //delay(10);
}

void lcdWriteJustData(byte data) {
  digitalWrite(d7, (data & 0x80) == 0x80);
  digitalWrite(d6, (data & 0x40) == 0x40);
  digitalWrite(d5, (data & 0x20) == 0x20);
  digitalWrite(d4, (data & 0x10) == 0x10);
  digitalWrite(d3, (data & 0x08) == 0x08);
  digitalWrite(d2, (data & 0x04) == 0x04);
  digitalWrite(d1, (data & 0x02) == 0x02);
  digitalWrite(d0, (data & 0x01) == 0x01);
}

void setDataPinsForOutput() {
  pinMode(d0, OUTPUT);
  pinMode(d1, OUTPUT);
  pinMode(d2, OUTPUT);
  pinMode(d3, OUTPUT);
  pinMode(d4, OUTPUT);
  pinMode(d5, OUTPUT);
  pinMode(d6, OUTPUT);
  pinMode(d7, OUTPUT);
}

void testDataSheetSection9() {
  Serial.println("Running Test 2");

  Serial.println("Step  4");
  //  4 Set display start address and display regions
  lcdWriteCommand(SCROLL);
  lcdWriteData(0x00);     // P1 (SAD 1 L)
  lcdWriteData(0x00);     // P2 (SAD 1 H)
  lcdWriteData(0x80);     // P3 (SL 1)
  lcdWriteData(0x00);     // P4 (SAD 2 L)
  lcdWriteData(0x10);     // P5 (SAD 2 H)
  lcdWriteData(0x80);     // P6 (SL 2)
  lcdWriteData(0x00);     // P7 (SAD 3 L)
  lcdWriteData(0x04);     // P8 (SAD 3 H)
  //lcdWriteData(0x00);     // P9 (SAD 4 L)
  //lcdWriteData(0x30);     // P10 (SAD 4 H)
  
  Serial.println("Step  5");
  //  5 Set Horizontal Scroll position
  lcdWriteCommand(HDOT_SCR);
  lcdWriteData(0x00);
  
  Serial.println("Step  6");
  //  6 Set display overlay format
  lcdWriteCommand(OVLAY);
  lcdWriteData(0x01);
  
  Serial.println("Step  7");
  //  7 Set display off
  lcdWriteCommand(DISP_OFF);
  lcdWriteData(0x56);

  Serial.println("Step  8");
  //  8 Clear data in first layer with 20H (space character)
  clearTextLayer();

  Serial.println("Step  9");
  //  9 Clear data in second layer with 00H (blank data)
  clearGraphicsLayer();

  Serial.println("Step 10");
  // 10 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x00);
  lcdWriteData(0x00);

  Serial.println("Step 11");
  // 11 Set Cursor type
  lcdWriteCommand(CSRFORM);
  lcdWriteData(0x04);
  lcdWriteData(0x86); 
  
  Serial.println("Step 12");
  // 12 Set display on
  lcdWriteCommand(DISP_ON);

  Serial.println("Step 13");
  // 13 Set Cursor direction - Right
  lcdWriteCommand(CSRDIR_R);

  Serial.println("Step 14");
  // 14 Write characters
  lcdWriteCommand(MWRITE);
  lcdWriteData(0x20);
  lcdWriteData(0x45);
  lcdWriteData(0x50);
  lcdWriteData(0x53);
  lcdWriteData(0x4F);
  lcdWriteData(0x4E);

  Serial.println("Step 15");
  // 15 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x00);
  lcdWriteData(0x10);

  Serial.println("Step 16");
  // 16 Set Cursor direction - Down
  lcdWriteCommand(CSRDIR_D);
  
  Serial.println("Step 17");
  // 17 Fill square
  lcdWriteCommand(MWRITE);
  for(int i0=0; i0<9; i0++) {
    lcdWriteData(0xFF);
  }

  Serial.println("Step 18");
  // 18 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x01);
  lcdWriteData(0x10);

  Serial.println("Step 19");
  // 19 Fill square
  lcdWriteCommand(MWRITE);
  for(int i0=0; i0<9; i0++) {
    lcdWriteData(0xFF);
  }

  Serial.println("Step 20");
  // 20 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x02);
  lcdWriteData(0x10);

  Serial.println("Step 21");
  // 21 Fill square
  lcdWriteCommand(MWRITE);
  for(int i0=0; i0<9; i0++) {
    lcdWriteData(0xFF);
  }

  Serial.println("Step 22");
  // 22 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x03);
  lcdWriteData(0x10);

  Serial.println("Step 23");
  // 23 Fill square
  lcdWriteCommand(MWRITE);
  for(int i0=0; i0<9; i0++) {
    lcdWriteData(0xFF);
  }

  Serial.println("Step 24");
  // 24 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x04);
  lcdWriteData(0x10);

  Serial.println("Step 25");
  // 25 Fill square
  lcdWriteCommand(MWRITE);
  for(int i0=0; i0<9; i0++) {
    lcdWriteData(0xFF);
  }

  Serial.println("Step 26");
  // 26 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x05);
  lcdWriteData(0x10);

  Serial.println("Step 27");
  // 27 Fill square
  lcdWriteCommand(MWRITE);
  for(int i0=0; i0<9; i0++) {
    lcdWriteData(0xFF);
  }

  Serial.println("Step 28");
  // 28 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x06);
  lcdWriteData(0x10);

  Serial.println("Step 29");
  // 29 Fill square
  lcdWriteCommand(MWRITE);
  for(int i0=0; i0<9; i0++) {
    lcdWriteData(0xFF);
  }

  Serial.println("Step 30");
  // 30 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x00);
  lcdWriteData(0x01);

  Serial.println("Step 31");
  // 31 Set Cursor direction - Right
  lcdWriteCommand(CSRDIR_R);

  Serial.println("Step 32");
  // 32 Write more text
  lcdWriteCommand(MWRITE);
  lcdWriteData(0x44);
  lcdWriteData(0x6F);
  lcdWriteData(0x74);
  lcdWriteData(0x20);
  lcdWriteData(0x4D);
  lcdWriteData(0x61);
  lcdWriteData(0x74);
  lcdWriteData(0x72);
  lcdWriteData(0x69);
  lcdWriteData(0x78);
  lcdWriteData(0x20);
  lcdWriteData(0x4C);
  lcdWriteData(0x43);
  lcdWriteData(0x44);  
  
  
  Serial.println("Done with Datasheet Section 9 Sample");
}

void test2(int testNum) {
  
  Serial.println("Running Test 2");

  Serial.println("Step  4");
  //  4 Set display start address and display regions
  lcdWriteCommand(SCROLL);
  lcdWriteData(0x00);     // P1 (SAD 1 L)
  lcdWriteData(0x00);     // P2 (SAD 1 H)
  lcdWriteData(0x80);     // P3 (SL 1)
  lcdWriteData(0x00);     // P4 (SAD 2 L)
  lcdWriteData(0x10);     // P5 (SAD 2 H)
  lcdWriteData(0x80);     // P6 (SL 2)
  lcdWriteData(0x00);     // P7 (SAD 3 L)
  lcdWriteData(0x04);     // P8 (SAD 3 H)
  
  Serial.println("Step  5");
  //  5 Set Horizontal Scroll position
  lcdWriteCommand(HDOT_SCR);
  lcdWriteData(0x00);
  
  Serial.println("Step  6");
  //  6 Set display overlay format
  lcdWriteCommand(OVLAY);
  lcdWriteData(0x01);
  
  Serial.println("Step  7");
  //  7 Set display off
  lcdWriteCommand(DISP_OFF);
  lcdWriteData(0x56);

  Serial.println("Step  8");
  //  8 Clear data in first layer with 20H (space character)
  clearTextLayer();

  Serial.println("Step  9");
  //  9 Clear data in second layer with 00H (blank data)
  clearGraphicsLayer();

  Serial.println("Step 10");
  // 10 Set cursor address
  lcdWriteCommand(CSRW);
  lcdWriteData(0x00);
  lcdWriteData(0x00);

  Serial.println("Step 11");
  // 11 Set Cursor type
  lcdWriteCommand(CSRFORM);
  lcdWriteData(0x04);
  lcdWriteData(0x86); 
  
  Serial.println("Step 12");
  // 12 Set display on
  lcdWriteCommand(DISP_ON);
  //lcdWriteData(0x16);

  Serial.println("Step 13");
  // 13 Set Cursor direction - Right
  lcdWriteCommand(CSRDIR_R);

  Serial.println("Step 14");
  // 14 Write characters
  writeNumbers(testNum);

  
  Serial.println("Done with Test 2");
}


void writeNumbers(int numQty) {
  byte numZero = 0x30;
  int idx = 0;
  byte data = 0x00;
  byte offset = 1;
  
  lcdWriteCommand(MWRITE);
  while(idx < numQty) {
    if(offset > 9)
      offset = 0;

    data = numZero + offset;
    lcdWriteData(data);
    
    offset++;
    idx++;
  }
}

I plan to post more information as the project progresses. I do want to mention a few things that I found out in regards to the display.

  • You may wonder if the HG25504 is single or dual-panel display. It is a one panel display. This becomes obvious when you look at the ICs on the back of the display. The columns are driven by four HD66204FC Dot Matrix LCD column driver with 80-channels. If each column was used on these chips, they could drive 320 columns. This is 64 more columns than the display has but no where near 512 columns which would be required for a dual-panel configuration.
  • Included ICs and function
    • HD66204FC (Qty 4) Dot Matrix LCD column driver with 80-channels
    • HD66205FC (Qty 2) Dot Matrix LCD common driver with 80-channels
    • SED1330F (Qty 1) LCD Controller
    • HY6264A (Qty 1) Static RAM (8K bytes)
    • KA324D (Qty 1) Quad Operational Amplifier
  • Vo (LCD Contrast Voltage) – You really do need to apply at least -10V to Vo in respect to ground. There are some posts regarding this display stating that tying it to ground is enough but it is not. I had applied a negative voltage but was only seeing something when Vo was near ground potential. I was able to initialize the LCD but could not see anything displayed. I knew the screen was initialized because with Vo being close to ground potential, I saw one or more lines on the LCD when it was initially powered up. When I initialized the LCD, the line(s) were gone. I was getting frustrated as I could not display anything on the screen after initializing it. When I finally used a different power supply, I could see that I had been doing things right.
  • Power Requirements (You may have different results)
    • LCD Contrast (-10.5VDC @ 3.5mA)
    • LCD Logic (5VDC @ 10mA)
    • Arduino Uno (5VDC @ 10mA
  • The SED1330F supports 8080 and 6800 family processors. This matters as the LCD is wired for one or the other and the control lines change function based on the wiring of the LCD. Section 2.4.3 of the datasheet specifies that SEL1 and SEL2 determine the operation. Both SEL1 and SEL2 are connected to ground on the LCD therefore it is operating in 8080 mode.

CNC Machine

I have had a MyDIYCNC Machine sitting around for a few years now. I was having some problems with the controller boards so I set it aside and am just getting back to take another look at it. I found that one of the boards that was sent to me was indeed bad but MyDIYCNC no longer sells machines or parts. I then decided to go to Amazon and pick out a controller board to try. I picked the SainSmart CNC TB6560 3 Axis Stepper Motor Driver Controller Board & Cable. This board seems to work quite well. I have been having a bit of a time getting it to work properly in LinuxCNC but I have got it to home and move but it seems to be at 1/2 scale. I am still tweaking with the settings to see if I can get it to work 100%.

A few notes about wiring and hardware. The MyDIYCNC instructions refer to the motor which moves the Z axis carrier as the Y axis. It appears that it should really be the X axis and the table should be the Y axis. If it were the Y axis, the home position would be in the wrong corner of the machine. I played with the configuration a bit to see if I could get it to work as expected but I had no luck. Finally when I decided to try to swap the X and Y axes did home line up in the correct corner. I could have swapped A & B around on the Y motor and that may have reversed the direction of the motor but I did not want to go there. Swapping the axes made the most sense.

Here is a short video of a test of the CNC. The spindle has a ink cartage in it and is simply running the default LinuxCNC project. The drawing should be 5.3 inches wide but is only half that size.

Here are the settings for LinuxCNC.

001
Base Information

  • Machine Name: MyDIYCNC_inches
  • Axis configuration: XYZ
  • Reset Default machine units: Inch
  • Driver type: Other
  • Driver Timing Settings (The Stepper Drive Timing page on linux.org states that 150,000 ns should be used for all values however the current version of LinuxCNC has a max value of 100,000.)
    • Step Time: 100000
    • Step Space: 100000
    • Direction Hold: 100000
    • Direction Setup: 100000
  • Base Period Maximum Jitter: 9000

002
Parallel Port 1

  • Outputs (PC to Mill):
    • Pin 1: Amplifier Enable (Invert)
    • Pin 2: X Step
    • Pin 3: X Direction
    • Pin 4: Y Step
    • Pin 5: Y Direction
    • Pin 6: Z Step
    • Pin 7: Z Direction
    • Pin 8: Unused
    • Pin 9: Unused
    • Pin 14: Spindle ON (Invert)
    • Pin 16: Unused
    • Pin 17: Unused
  • Inputs (Mill to PC):
    • Pin 10: Both Limit + Home X (Invert)
    • Pin 11: Both Limit + Home Y (Invert)
    • Pin 12: Both Limit + Home Z (Invert)
    • Pin 13: ESTOP In
    • Pin 15: Unused
  • Parport Base Address: 0
  • Output pinout presets: Sherline (The value here is not important. It is actually used with the “Preset” button to load values.)

003
Options

Selections here really do not matter. I have not figured out how to use these yet. I may look into it more in the future.

004
Axis X

  • Motor steps per revolution: 800 (Steppers included with MyDIYCNC are 50 steps per revolution. The TB6560 board has the switches set for 1/16 microstepping. 50 x 16 = 800)
  • Driver Microstepping: 2.0 (Someone posted that 2 meant that microsteping was being used. I had this set to 32 earlier.)
  • Pulley teeth (Motor:Leadscrew): 1.0:1.0 (All axes are direct drive so they are all 1:1.)
  • Leadscrew Pitch: 20.0
  • Maximum Velocity: 0.4
  • Maximum Acceleration: 30.0
  • Home location: 0.125 This took awhile to get. If using the limit switches as home switches as well, we need to back the machine off so that the limit switches are not active when at home position. I choose to back them off 1/8 inch on all axes.)
  • Table travel: 0.0 to 5.5
  • Home Switch Location: 0.0
  • Home Search velocity: -0.05
  • Home Latch direction: Same

005
Axis Y

  • Motor steps per revolution: 800
  • Driver Microstepping: 2.0
  • Pulley teeth (Motor:Leadscrew): 1.0:1.0
  • Leadscrew Pitch: 20.0
  • Maximum Velocity: 0.4
  • Maximum Acceleration: 30.0
  • Home location: 0.125
  • Table travel: 0.0 to 8.0
  • Home Switch Location: 0.0
  • Home Search velocity: -0.05
  • Home Latch direction: Same

006
Axis Z

  • Motor steps per revolution: 800
  • Driver Microstepping: 2.0
  • Pulley teeth (Motor:Leadscrew): 1.0:1.0
  • Leadscrew Pitch: 20.0
  • Maximum Velocity: 0.4
  • Maximum Acceleration: 30.0
  • Home location: -0.125
  • Table travel: -4.0 to 0.0
  • Home Switch Location: 0.0
  • Home Search velocity: 0.05
  • Home Latch direction: Same

007
Almost Done

008
Do you want to quit?

Screenshot added for completeness

I plan to continue to look into what is going on with the scaling and settle on the correct settings or at least settings which will work.

Test Video

I would like to add more videos to the blog. One of the problems that I have had is the time it takes to perform post processing on videos to add different sources and information. I found the Open Broadcaster Software application and started messing around with it and found that it is quite good, once you get use to how it works. Here is my first attempt at creating a video with the software.

BTW: Yes, I totally ripped off some ideas from Adafruit. I’m not too creative so I copied what I like. I will attempt to change it but it is tough as Limor and Phil have created a very nice format for the shows that Adafruit produces. I also like Ben Heck and Dave Jones (EEVBlog) videos as well but I seem to watch more of the videos Adafruit puts out.

Here is my first recording.

I2C Communications between Raspberry Pi and Arduino – Update

Over the past few days, I have been able to bit bang the I2C bus with the PIGPIO library. I found a very helpful example at http://raspberrypi.stackexchange.com/questions/3627/is-there-an-i2c-library/4052 which was posted by crj11. This example was using the pigpiod_if.h library. This worked well but required the application to be run with elevated privileges (sudo) which was not acceptable as I needed to run the application from a Python script which in turn was running every 5 minutes from a cron job. The final solution was to use the pigpiod_if2.h and run the pigpio daemon on startup.

The final solution has been running for a few days with three sensors connected over a total of 9 feet (~3 meters) of cable. The data has been logged at Adafruit.IO which I have made public. I may remove or rename the Dashboard in the near future so here is a screenshot of the page.
adafruit_io_v0.1.0

I have also updated the GitHub site for the project so there are now two releases available. Version RC_0.0.1 is the version using the hardware for I2C control and version RC_0.1.0 is the bit bang version.

I still have more work to do to make this project valuable to others. I plan to create some better documentation on the project and provide a full write-up to allow someone to follow along and build there own from start to finish. Right now, 80% to 90% is captured in various places but there are obvious gaps such as the connection to the Raspberry Pi. One can figure this missing information out by looking through the right source files and piece it together however I do not like it when I find a project write-up that is only 80% to 90% documented. It is still better than nothing or only 10% to 25% though.

I hope someone will find some of the information here useful.

Sensor with one cable connected

I2C Communications between Raspberry Pi and Arduino – Update, BOM, and Source Control

Update

I have been working on this project over the past couple of weeks when I have free time but have not been posting updates. This is a general update which is why the title is different from the other posts regarding this project.

My boards from OSH Park arrived last week. I was able to populate them and test them out. Fortunately I did not make any errors on the PCB or schematic so they all worked as designed. There are a few things that I would change on a future version if I choose to make another version of the board.

  1. I would put the ICSP header on the bottom of the board so it does not stick out from the front. This would make it much easier to assemble and would make it possible to not have any exposed circuitry which may allow the device to be damaged from static electricity.
  2. I would move the resistors toward the bottom of the board if possible. It would allow the DHT11 sensor to stick out further from the case.
  3. I would also try to push the ATtiny85 a little further towards the bottom for the same reason as the resistors.

Currently I am looking to bit bang the I2C bus on the Raspberry Pi. I seem to have gotten around the clock stretching issue if there is only one device connected to the I2C bus but as soon as I add another device, the clock stretching becomes an issue again. I really wish that the Pi Foundation would work with Broadcom and fix the issue with the I2C bus.

Here are some pictures.

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Bill of Materials (BOM)

Materials List (For One Sensor)

  • QTY 1 – PCB (Source: OSH Park)
  • QTY 2 – 3.5mm 4 Pole Audio Jack, J1 & J2 (Source: MCM Electronics NOTE: I ordered 27-9485 but received ones which look like 27-9487)
  • QTY 1 – 2×3 Position Male Header 2.54mm Pitch, JP1 (Source: MCM Electronics NOTE: This is a 2×13 header. You will need to cut it for 2×3 header.)
  • QTY 1 – T-1 3mm LED, LED1 (Source: MCM Electronics NOTE: May choose another color)
  • QTY 1 – CDS Photoresistor Photoelectric 5549 GL5549, PH1 (Source: Ebay)
  • QTY 2 – Resistor 1/4W 10K Ohm, R1 & R2 (Source: MCM Electronics)
  • QTY 1 – Resistor 1/4W 220 Ohm, R3 (Source: MCM Electronics)
  • QTY 1 – DHT11 Digital Temperature & Humidity Sensor Moudle, SE1 (Source: Ebay)
  • QTY 1 – ATMEL ATtiny85, U1 (Source: Newark)

Materials List for Raspberry Pi Hat

  • Qty 1 – Perfboard (Source: Adafruit)
  • Qty 1 – GPIO Header for Raspberry Pi NOTE: The one you will need depends on which model of Raspberry Pi you are using. (Source: Adafruit 2×13 Header for original Raspberry Pi or 2×20 Header for newer Raspberry Pi)
  • QTY 1 – 3.5mm 4 Pole Audio Jack (Source: MCM Electronics NOTE: I ordered 27-9485 but received ones which look like 27-9487)
  • Optional items

Source Control

I have added the source files for the Hardware and Software onto GitHub. I did this so the community may have access to the files and any updates to them. I mainly did it because I was having a hard time remembering which set of files I last worked with especially if a few days went by when I could not work on the project. I think this is a win-win for me and anyone interested in this project.

The files are located at https://github.com/TeelSys/TeelSys_THL. When you first go to the page, it may look like there are mo project files included in the project. If that is the case it is because I am still trying to get everything working properly before I commit code to the master branch. You will see a button with the text “Branch: master” and a downward arrow. Click that button and select another branch such as “dev”. You will then see the project files in their current state.

If you wish to contribute, add a comment here or if you can request through GitHub, do that. I will reply once I see the request but keep in mind that it may be a few days.