Bad wiring on NHD-2.7-12864WDW3

TheogirarD

March 12, 2021 14:46

Hi,
I've just received a NHD-2.7-12864WDW3 and can't get it to light up a single pixel...
I've wired it as :
1 : GND
2 : +3V3
3 : not connected
4 : GPIO output (D/C)
5 : GND because I intend to write only on the screen (using timings on "Enable" instead of reading the response from the screen)
6 : GPIO output (EN)
7-14 : D0-D7 GPIO outputs (used as 6800 parallel interface)
15 : not connected
16 : +3V3 (I suppose I can never reset the screen ?)
17 : GND
18 : not connected
19 : +3V3
20 : +3V3 (to use the 6800 parallel interface)

I don't know where I'm wrong but with this wiring nothing happens...
I tried an initialisation sequence such as :

WriteCommand(0xAE); (display OFF)
WriteCommand(0xC7);
WriteCommand(0xC1); (set contrast)
WriteCommand(0xA5); (set display mode as all LEDs lit up)
WriteCommand(0xAF); (display ON)

But still nothing...
I tested WriteCommand with leds and it outputs the rigth binary data...
Just in case, I maintain Enable LOW during 10µs for each command and wait 5ms between each command. (Which far exceed the datasheet timing)
I know I'm getting something wrong but I can't find what's going on !
Is there a simpler way to light the screen to check if my wiring is correct ?
I think the code should be correct because I ran a Hitachi HD44780-based LCD screen with pretty much the same code (just changed the commands)...
Thanks a lot for your future answer !

Comments

8 comments

Ted M.

NHD Staff

March 15, 2021 10:12

Hi TheogirarD,

The reset line needs to be controlled during initialization.

https://newhavendisplay.com/content/specs/NHD-2.7-12864WDW3.pdf

digitalWrite(RES, LOW); //pull /RES (pin #16) low
delayUS(200); //keep /RES low for minimum 200µs
digitalWrite(RES, HIGH); //pull /RES high
delayUS(200); //wait minimum 200µs before sending commands

Please try connecting the reset line to a GPIO and follow the initialization code below.

void NHD12864WDY3_Init(void){
digitalWrite(RES, LOW); //pull /RES (pin #16) low
delayUS(200); //keep /RES low for minimum 200µs
digitalWrite(RES, HIGH); //pull /RES high
delayUS(200); //wait minimum 200µs before sending commands
 writeCommand(0xAE); //display OFF
 writeCommand(0xB3); //set CLK div. & OSC freq.
 writeData(0x91);
 writeCommand(0xCA); //set MUX ratio
 writeData(0x3F);
 writeCommand(0xA2); //set offset
 writeData(0x00);
 writeCommand(0xAB); //function selection
 writeData(0x01);
 writeCommand(0xA0); //set re-map
 writeData(0x16);
 writeData(0x11);
 writeCommand(0xC7); //master contrast current
 writeData(0x0F);
 writeCommand(0xC1); //set contrast current
 writeData(0x9F);
 writeCommand(0xB1); //set phase length
 writeData(0xF2);
 writeCommand(0xBB); //set pre-charge voltage
 writeData(0x1F);
 writeCommand(0xB4); //set VSL
 writeData(0xA0);
 writeData(0xFD);
 writeCommand(0xBE); //set VCOMH
 writeData(0x04);
 writeCommand(0xA6); //set display mode
 writeCommand(0xAF); //display ON

Regards,

TheogirarD

March 15, 2021 14:21
Hi,
thanks a lot for your answer ! I indeed realized that RES was missing. I also figured out another error because one of the data bus was not a gpio.
But even with those problems solved there is still an issue...
I can now send commands like display ON/OFF and display mode (and it works pretty well) ! But the screen doesn't seem to understand data as data ! Whatever the data I send, nothing happens.
If I send a data byte like 0xAE it is unterstood by the OLED as a command and it shuts down (0xAE is the command for display OFF).
I double-checked the D/C pin, it is receiving a UP (3V3). I tried adding a resistor to fix the input. May I have broken the input due to my anterior bad commands ?!
Does the D/C pin need a resistor (I'm sending the code from a beaglebone GPIO) ?

Here is the code I use for writeCommand
```
void OLED::writeCommand(uint8_t Commande)
{
  uint8_t Binaire(Commande);

  PinRe.write(0);
  WaitForUnbusy(100);
  for(int i(0); i<8; i++)
  {
    uint8_t masque(pow(2,i));
    bool Value(Binaire & masque);
    DataPin[i].write(Value);
  }
  ShotEnable();
  WaitForUnbusy(100);
}
```
This code is fully functionnal but the one for writeData (following) isn't... The only difference is the PinRe UP (this pin is connected to D/C) !
```
void OLED::writeData(uint8_t Commande)
{
  uint8_t Binaire(Commande);

  PinRe.write(1);
  WaitForUnbusy(100);
  for(int i(0); i<8; i++)
  {
    uint8_t masque(pow(2,i));
    bool Value(Binaire & masque);
    DataPin[i].write(Value);
  }
  ShotEnable();
  WaitForUnbusy(100);
}
```
Sorry if the problem seems trivial...
0

Ted M.

NHD Staff

March 16, 2021 15:16

Hi TheogirarD,

Please refer to this example code for writing to the display. 2 Pixels must be written at a time.

void newWrite2Pixels(unsigned char xPos, unsigned char yPos, unsigned char pixel1, unsigned char pixel2){
    if(pixel1>=1) pixel1 = 0xFF;      //set 1st pixel value to ON
    else pixel1 = 0x00;       //set 1st pixel value to OFF
    if(pixel2>=1) pixel2 = 0xFF;      //set 2nd pixel value to ON
    else pixel2 = 0x00;       //set 2nd pixel value to OFF
    if(xPos>127) xPos = 127;      //boundary check (MIN xPos = 0, MAX xPos = 127)
    xPos = xPos/2;                //account for GDDRAM address mapping
    xPos+=28;                    //account for GDDRAM address mapping
    if(yPos>63) yPos = 63;        //boundary check (MIN yPos = 0, MAX yPos = 63)
    newSetColumn(xPos,xPos);  //set column (x-axis) start/end address
    newSetRow(yPos,yPos);        //set row (y-axis) start/end address
    writeRAM();                //single byte command (0x5C) to initiate pixel data write to GDDRAM;
    writeData(pixel1);     //write 1st of 2 pixels to the display
    writeData(pixel2);     //write 2nd of 2 pixels to the display
}
void newSetColumn(unsigned char xStart, unsigned char xEnd){
    writeCommand(0x15);       //set column (x-axis) start/end address
    writeData(xStart);          //column start; 28 is left-most column
    writeData(xEnd);          //column end; 91 is right-most column
}
void newSetRow(unsigned char yStart, unsigned char yEnd){
    writeCommand(0x75);       //set row (y-axis) start/end address
    writeData(yStart);          //row start; 0 is top row
    writeData(yEnd);          //row end; 63 is bottom row
}



void newDisplayArray12864(const unsigned char arr[]){
    unsigned int i, j; 
    newSetColumn(28,91);
    newSetRow(0,63);
    writeRAM();
    for(i=0;i<1024;i++){ //translate each byte/bit into pixel data
      for(j=0;j<8;j++){
        if(((arr[i]<<j)&0x80)==0x80){
          writeData(0xFF);
        }
        else{
          writeData(0x00);
        }
      }
    }     
}


const unsigned char NHDlogo [] = { //128x64 monochrome bitmap, horizontal pixel arrangement, 8-pixels per byte, 1,024 bytes
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};

Regards,

TheogirarD

March 16, 2021 15:48
Hello,
Yes I'm using the whole code provided in the datasheet including draw2Pixels !
But when I use only the init code (the one you've sent before) shows a pixel snowy pattern (attached picture).
This is due to a bad interpretation from the screen (because there is probably something I'm doing the wrong way).
Neither draw2Pixels nor clearDisplay are working ! Because they both require data reception. And data is understood as command...
I checked multiple times but the pin 4 (D/C) is indeed tied to 3V3 when I try to send Data and to GND when I send command...
Apart from data, I can successfully send each command (but the one that require data parameters are not applied)...
Sorry if my explanations are bad...
Thanks a lot again for your patience and your answer !
0
Ted M.
NHD Staff

March 25, 2021 15:48
Hi TheogirarD,

Check the D/C line to be sure it is active at the correct timing and it's going low enough to toggle the Data line.
Try changing the GPIO pin that controls it or you can add a pull down resistor to the D/C line.

Regards,
0

TheogirarD

March 26, 2021 15:48

Hi !
Thanks again for your patience !
I've purchased another screen (NHD-2.7-12864WDY3) to check if I wasn't using a broken product and... No, the result is strictly the same (the picture is attached).
I checked with LEDs and delays increased, the lighting sequence of the pins is exactly as coded...
I can't understand the error... Do you have any idea what could cause the weird screen (the one on the attached picture) to show up ?
Here is the whole code I'm using :

#include "OLEDscreen.h"
#include <vector>
#include <string>
#include <cstdint>
#include <unistd.h>
#include <math.h>
#include <Bela.h>
#include <Gpio.h>


//Test :
#include <iostream>

using namespace std;



void OLED::writeCommand(uint8_t Commande)
{
  uint8_t Binaire(Commande);
 
  for(int i(0); i<8; i++)
  {
    uint8_t masque(pow(2,i));//on genere 0001000 a la ieme position
    bool Value(Binaire & masque); //Value prend la valeur booleene du ieme bit
    DataPin[i].write(Value);//Update the pin
  }

  PinRe.write(0);
  WaitForUnbusy(100);
  ShotEnable();
  WaitForUnbusy(100);
}

void OLED::writeData(uint8_t Commande)
{
  uint8_t Binaire(Commande);
 
  for(int i(0); i<8; i++)
  {
    uint8_t masque(pow(2,i));//on genere 0001000 a la ieme position
    bool Value(Binaire & masque); //Value prend la valeur booleene du ieme bit
    DataPin[i].write(Value);// Update the pin
  }

  PinRe.write(1);
  WaitForUnbusy(100);
  ShotEnable();
  WaitForUnbusy(100);
 
}


void OLED::ShotEnable()
{
  PinE.write(0);
   WaitForUnbusy(100);
  PinE.write(1);
}

void OLED::WaitForUnbusy(int delayInUs)
{
  usleep(delayInUs);
}

void OLED::initDisplay()
{
PinRes.write(0); //pull /RES (pin #16) low
WaitForUnbusy(200); //keep /RES low for minimum 200µs
PinRes.write(1); //pull /RES high
WaitForUnbusy(200);

writeCommand(0xAE); //display OFF
writeCommand(0xB3); //set CLK div. & OSC freq.
writeData(0x91);
writeCommand(0xCA); //set MUX ratio
writeData(0x3F);
writeCommand(0xA2); //set offset
writeData(0x00);
writeCommand(0xAB); //function selection
writeData(0x01);
writeCommand(0xA0); //set re-map
writeData(0x16);
writeData(0x11);
writeCommand(0xC7); //master contrast current
writeData(0x0F);
writeCommand(0xC1); //set contrast current
writeData(0x9F);
writeCommand(0xB1); //set phase length
writeData(0xF2);
writeCommand(0xBB); //set pre-charge voltage
writeData(0x1F);
writeCommand(0xB4); //set VSL
writeData(0xA0);
writeData(0xFD);
writeCommand(0xBE); //set VCOMH
writeData(0x04);
writeCommand(0xA6); //set display mode
writeCommand(0xAF); //display ON
}


OLED::OLED(int pinRe, int pinE, int pinRES, int dataPin[])
{

  for(int i(0); i < 8; i++)
  {
    DataPin[i].open(dataPin[i], OUTPUT);
  }

  PinE.open(pinE, OUTPUT);
  PinRe.open(pinRe, OUTPUT);
  PinRes.open(pinRES, OUTPUT);
  PinE.write(1);
  PinRe.write(0);
 
  initDisplay();

}


void OLED::writeRAM()
{
writeCommand(0x5C);
}

void OLED::setColumn(unsigned char xStart, unsigned char xEnd)
{
writeCommand(0x15); //set column (x-axis) start/end address
writeData(xStart); //column start; 28 is left-most column
writeData(xEnd); //column end; 91 is right-most column
}

void OLED::setRow(unsigned char yStart, unsigned char yEnd)
{
writeCommand(0x75); //set row (y-axis) start/end address
writeData(yStart); //row start; 0 is top row
writeData(yEnd); //row end; 63 is bottom row
}
void OLED::clearDisplay(void)
{
setColumn(0,127); //set column (x-axis) start/end address
setRow(0,63); //set row (y-axis) start/end address
writeRAM(); //single byte command (0x5C) to initiate pixel data write to GDDRAM;
for(int i=0;i<8192;i++){ // ((91-28)+1)*((63-0)+1)
writeData(0x00);
writeData(0x00);
}
}
void OLED::draw2Pixels(unsigned char xPos, unsigned char yPos, unsigned char pixel1, unsigned char pixel2)
{
if(pixel1>=1) pixel1 = 0xFF; //set 1st pixel value to ON
else pixel1 = 0x00; //set 1st pixel value to OFF
if(pixel2>=1) pixel2 = 0xFF; //set 2nd pixel value to ON
else pixel2 = 0x00; //set 2nd pixel value to OFF
if(xPos>127) xPos = 127; //boundary check (MIN xPos = 0, MAX xPos = 127)
xPos = xPos/2; //account for GDDRAM address mapping
xPos+=28; //account for GDDRAM address mapping
if(yPos>63) yPos = 63; //boundary check (MIN yPos = 0, MAX yPos = 63)
setColumn(xPos,xPos); //set column (x-axis) start/end address
setRow(yPos,yPos); //set row (y-axis) start/end address
writeRAM(); //single byte command (0x5C) to initiate pixel data write to GDDRAM;
writeData(pixel1); //write 1st of 2 pixels to the display
writeData(pixel2); //write 2nd of 2 pixels to the display
}

void OLED::displayArray12864(const unsigned char arr[])
{ //display 128x64 monochrome bitmap, horizontal pixel arrangement, 8-pixels per byte
unsigned int i, j;
setColumn(28,91); //set column (x-axis) start/end address
setRow(0,63); //set row (y-axis) start/end address
writeRAM(); //single byte command (0x5C) to initiate pixel data write to GDDRAM;
for(i=0;i<1024;i++)
{ //translate each byte/bit into pixel data
for(j=0;j<8;j++)
{
if(((arr[i]<<j)&0x80)==0x80)
{
writeData(0xFF);
}
else
{
writeData(0x00);
}
}
}
}

I also tried with a pull down resistor on D/C pin... Here is what happens on the LED when I send a data :
1) The byte appears on the Data pins D0-7 in the right order (D0 is the first bit)
2) The D/C pin goes up
3) The Enable pin (which is always up) falls down to latch Data
CS is always tied to LOW, R/W is always tied to LOW

I'm pretty desperate, I think this will be my last attempts to get it to work... If you have any idea or suggestion about what I could try, I would gladly try it !
Thanks !

TheogirarD

March 27, 2021 15:57
Hi !
Sorry, my bad, I found the issue !
I was maintaining the enable pin high all the time, thinking that only the falling edge was important ! It is the case in the other 6800 parallel interface that I used so I thought it was similar.
But no, to get it to work, I have to tie up the enable pin after the data is sent on the data and after the D/C pin is correctly tied. And then I latch the data by tying low the enable pin !
Thanks a lot for your answers. I hope this can be useful to other people ! Perhaps you could add this specification to the datasheet as the process differs from other 6800 interface such as the classic LCD Hitachi !
0
Ted M.
NHD Staff

March 31, 2021 15:48
Hi TheogirarD,

Thanks for your update! It's great to hear you have it working.

Best Regards,
0

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