Author: richteel

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);
}

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.

#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.