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SPI Comms With ILI9341

 
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Backfire



Joined: 12 Oct 2020
Posts: 46

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SPI Comms With ILI9341
PostPosted: Mon Oct 12, 2020 10:28 am     Reply with quote
Hi everyone,
I was hoping for some advice on an issue I'm having trying to get a PIC (specifically a 18F2455) communicating with a ILI9341 based GFX LCD over SPI.

I've used the library from adafruit for the CCS C compiler as a jumping off point, and attach my modified code below for reference.

I just can't seemingly get the display to, well... display anything. I'm awaiting delivery of a cheap logic analyser to look into things further, but until then I thought I'd see if anyone could point out if I'm missing anything simple/obvious, as this is my first foray into SPI comms with CCS.

My hardware connections are all direct, and are listed below, the screen has 3.2V stable d.c. power, and does illuminate, just routines are not producing anything on the display.

PIC RB1 -> LCD SCK
PIC RC4 -> LCD CS
PIC RC5 -> LCD RST
PIC RC6 -> LCD D/C
PIC RC7 -> LCD SDAT

PIC is running from a 8MHz XTAL, PLL'ed up to 48MHz internally, and the LED flash routine of destiny runs without issues.

I know the code is ugly and needs MUCH further development, I've thrown this together to (attempt) the most basic of functionality first with everything clear and step-by-step.

Code:

#include <main.h>
#include <stdint.h>

#use spi (MASTER, SPI1, MODE=0, BITS=8)


// Screen function prototypes
void LCDHardReset(void);
void LCDInit(void);
void LCDEnableWrite(void);
void LCDDisableWrite(void);
void LCDWriteCmd(int8 Command);
void LCDSetAddressWindow(int16 x1, int16 y1, int16 w, int16 h);
void LCDRenderPixel(int16 x, int16 y, int16 colour);
void LCDSetCursor(int16 X, int16 Y);

void main()
{
   int8 i = 0;
   
   setup_adc_ports(AN0, VSS_VDD);
   setup_adc(ADC_CLOCK_INTERNAL | ADC_TAD_MUL_0);

   LCDHardReset();
   LCDInit();

   while(TRUE)
   {
      output_low(LED_BI_GRN);
      delay_ms(500);
      output_high(LED_BI_GRN);
      delay_ms(500);
     
      LCDRenderPixel(100, 100, 0xF800);
     
      i++;
   }
}



//-----------------------------------------------------------------------------
//
//-----------------------------------------------------------------------------

void LCDHardReset()
{
   output_high(SCREEN_RST);
   output_drive(SCREEN_RST);
   delay_ms(100);
   output_low(SCREEN_RST);
   delay_ms(100);
   output_high(SCREEN_RST);
   delay_ms(200);
}

void LCDInit()
{
   output_high(SCREEN_CS);
   output_drive(SCREEN_CS);
   output_drive(SCREEN_DC);

   LCDEnableWrite();

   LCDWriteCmd(0xCB);
   spi_xfer(0x39);
   spi_xfer(0x2C);
   spi_xfer(0x00);
   spi_xfer(0x34);
   spi_xfer(0x02);

   LCDWriteCmd(0xCF);
   spi_xfer(0x00);
   spi_xfer(0xC1);
   spi_xfer(0x30);

   LCDWriteCmd(0xE8);
   spi_xfer(0x85);
   spi_xfer(0x00);
   spi_xfer(0x78);

   LCDWriteCmd(0xEA);
   spi_xfer(0x00);
   spi_xfer(0x00);
   
   LCDWriteCmd(0xED);
   spi_xfer(0x64);
   spi_xfer(0x03);
   spi_xfer(0x12);
   spi_xfer(0x81);
   
/*
   LCDWriteCmd(0xEF);
   spi_xfer(0x03);
   spi_xfer(0x80);
   spi_xfer(0x02);
*/

   LCDWriteCmd(0xF7);
   spi_xfer(0x20);
   
   // Power Control
   LCDWriteCmd(0xC0);
   spi_xfer(0x23);
   LCDWriteCmd(0xC1);
   spi_xfer(0x10);
   
   // VCOM Control
   LCDWriteCmd(0xC5);
   spi_xfer(0x3E);
   spi_xfer(0x28);
   LCDWriteCmd(0xC7);
   spi_xfer(0x86);
   
   // Memory Access Control
   LCDWriteCmd(0x36);
   spi_xfer(0x88);
   
/*
   // Vertical Scroll Start Address
   LCDWriteCmd(0x37);
   spi_xfer(0x00);
*/

   // Pixel Format Colour Mode
   LCDWriteCmd(0x3A);
   spi_xfer(0x55);
   
   // Frame Rate Control
   LCDWriteCmd(0xB1);
   spi_xfer(0x00);
   spi_xfer(0x18);
   
   // Display Function Control
   LCDWriteCmd(0xB6);
   spi_xfer(0x08);
   spi_xfer(0x82);
   spi_xfer(0x27);
   
   LCDWriteCmd(0xF2);
   spi_xfer(0x00);
   
   // Set Screen Gamma
   LCDWriteCmd(0x26);
   spi_xfer(0x01);
   
   // Positive Gamma Correction
   LCDWriteCmd(0xE0);
   spi_xfer(0x0F);
   spi_xfer(0x31);
   spi_xfer(0x2B);
   spi_xfer(0x0C);
   spi_xfer(0x0E);
   spi_xfer(0x08);
   spi_xfer(0x4E);
   spi_xfer(0xF1);
   spi_xfer(0x37);
   spi_xfer(0x07);
   spi_xfer(0x10);
   spi_xfer(0x03);
   spi_xfer(0x0E);
   spi_xfer(0x09);
   spi_xfer(0x00);
   
   // Negative Gamma Correction
   LCDWriteCmd(0xE1);
   spi_xfer(0x00);
   spi_xfer(0x0E);
   spi_xfer(0x14);
   spi_xfer(0x03);
   spi_xfer(0x11);
   spi_xfer(0x07);
   spi_xfer(0x31);
   spi_xfer(0xC1);
   spi_xfer(0x48);
   spi_xfer(0x08);
   spi_xfer(0x0F);
   spi_xfer(0x0C);
   spi_xfer(0x31);
   spi_xfer(0x36);
   spi_xfer(0x0F);

   LCDWriteCmd(0x11);
   delay_ms(150);
   LCDWriteCmd(0x2C);
   
   LCDWriteCmd(0x29);
   LCDWriteCmd(0x2C);

   LCDDisableWrite();
}

void LCDWriteCmd(int8 Command)
{
  output_low(SCREEN_DC);
  spi_xfer(Command);
  output_high(SCREEN_DC);
}

void LCDEnableWrite(void)
{
   output_low(SCREEN_CS);
}

void LCDDisableWrite(void)
{
   output_high(SCREEN_CS);
}

void LCDSetAddressWindow(int16 x1, int16 y1, int16 w, int16 h)
{
    int16 x2 = (x1 + w - 1), y2 = (y1 + h - 1);
   
    LCDWriteCmd(0x2A);
    spi_xfer(x1 >> 8);
    spi_xfer(x1);
    spi_xfer(x2 >> 8);
    spi_xfer(x2);
   
    LCDWriteCmd(0x2B);
    spi_xfer(y1 >> 8);
    spi_xfer(y1);
    spi_xfer(y2 >> 8);
    spi_xfer(y2);
   
    LCDWriteCmd( 0x2C);
}

void LCDRenderPixel(int16 x, int16 y, int16 colour)
{
    LCDEnableWrite();
   
    LCDSetCursor(x, y);
   
    spi_xfer(colour >> 8);
    spi_xfer(colour & 0xFF);
   
    LCDDisableWrite();
}


void LCDSetCursor(int16 X, int16 Y)
{

    LCDWriteCmd(0x2B);
    spi_xfer(X >> 8);
    spi_xfer(X & 0xFF);
    LCDWriteCmd(0x2C);
   
    LCDWriteCmd(0x2A);
    spi_xfer(Y >> 8);
    spi_xfer(Y & 0xFF);
    LCDWriteCmd(0x2C);
}


I'm using the IDE suite and PCH Compiler V5.094

Thanks for taking the time to read this folks!

- BackFire
temtronic



Joined: 01 Jul 2010
Posts: 9245
Location: Greensville,Ontario

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PostPosted: Mon Oct 12, 2020 10:47 am     Reply with quote
1st question, what VDD is the PIC running ? If 3 volts, that's below the spec as shown in figure 28.1 of the datasheet.....
Backfire



Joined: 12 Oct 2020
Posts: 46

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PostPosted: Mon Oct 12, 2020 10:50 am     Reply with quote
Hi temtronic,
system voltage is a stable, decoupled locally against HF interference, 3.2-3.3V d.c.

Thanks for your reply.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Oct 12, 2020 11:36 am     Reply with quote
Quote:

PIC RB1 -> LCD SCK
PIC RC4 -> LCD CS
PIC RC5 -> LCD RST
PIC RC6 -> LCD D/C
PIC RC7 -> LCD SDAT

On the 18F2455, pins C4 and C5 are "input only". They are not going to
work for the lcd chip select or reset lines.
Ttelmah



Joined: 11 Mar 2010
Posts: 19546

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PostPosted: Mon Oct 12, 2020 11:41 am     Reply with quote
and as has already been mentioned, the 18F2455, is not rated to run at
this voltage. You will commonly find that PIC's will work below their
rated voltage, but peripherals won't. I'd not be surprised to find that
the SPI won't work at this voltage.
The 18LF2455 (note the 'L'), is rated to run down at this voltage at
a maximum of about 20MHz.
Backfire



Joined: 12 Oct 2020
Posts: 46

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PostPosted: Mon Oct 12, 2020 2:51 pm     Reply with quote
Well... that certainly explains that! :-D

I already had some ‘L’ variants on order luckily, but I had straight-up missed the input-only port pins. Thanks for the feedback all, I’ll report back with an update on following the advice!

Cheers again.

- BackFire
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