RA8876LiteTeensy For Teensy T36 and T40

pd0lew · Apr 19, 2025

Dear group,

For the speed of my project I need to use external font rom ER3304_1 is this possible with the RA8876 7" display.

Best,

Johan

dundakitty · Apr 20, 2025

With an older version of the library I used

Code:

ExternalFontRom rom = RA8876_FONT_ROM_GT30L32S4W;
tft.initExternalFontRom(0, rom);
tft.selectExternalFont( RA8876_FONT_FAMILY_TIMES, RA8876_FONT_SIZE_16,
                RA8876_FONT_ENCODING_ASCII);

then to switch to Arial I only had to use

Code:

tft.selectExternalFont( RA8876_FONT_FAMILY_ARIAL, RA8876_FONT_SIZE_16,
                RA8876_FONT_ENCODING_ASCII);

I haven't tested with the current version of the library.

pd0lew · Apr 20, 2025

Not working on my RA8876 display

error: 'class RA8876_t3' has no member named 'initExternalFontRom'
35 | tft.initExternalFontRom(0, rom);

error: 'class RA8876_t3' has no member named 'selectExternalFont'

Best,
Johan

dundakitty · Apr 20, 2025

Here's the code from the library I've been using. The entries might be named something else in the current library:

Code:

void RA8876::initExternalFontRom(int spiIf, enum ExternalFontRom chip)
{
  // See data sheet figure 16-10
  // TODO: GT30L24T3Y supports FAST_READ command (0x0B) and runs at 20MHz. Are the other font chips the same?

  // Find a clock divisor. Values are in the range 2..512 in steps of 2.
  int divisor;
  uint32_t speed = 20000;  // 20MHz target speed
  for (divisor = 2; divisor <= 512; divisor += 2)
  {
    if (m_corePll.freq / divisor <= speed)
      break;
  }

  m_fontRomInfo.present = true;
  m_fontRomInfo.spiInterface = spiIf;
  m_fontRomInfo.spiClockDivisor = divisor;
  m_fontRomInfo.chip = chip;

  if (deBug & 0x4) {
    Serial.print("External font SPI divisor: ");
    Serial.println(divisor);
  }

  SPI.beginTransaction(m_spiSettings);

  // Ensure SPI is enabled in chip config register
  uint8_t ccr = readReg(RA8876_REG_CCR);
  if (!(ccr & 0x02))
    writeReg(RA8876_REG_CCR, ccr | 0x02);

  if (deBug & 0x4) {
    Serial.print("SFL_CTRL: ");
    Serial.println(((spiIf & 1) << 7) | 0x14, HEX);
  }
  writeReg(RA8876_REG_SFL_CTRL, ((spiIf & 1) << 7) | 0x14);  // Font mode, 24-bit address, standard timing, supports FAST_READ
  if (deBug & 0x4) {
    Serial.print("SPI_DIVSOR: ");
    Serial.println((divisor >> 1) - 1, HEX);
  }
  writeReg(RA8876_REG_SPI_DIVSOR, (divisor >> 1) - 1);
  if (deBug & 0x4) {
    Serial.print("GTFNT_SEL: ");
    Serial.println((chip & 0x07) << 5, HEX);
  }
  writeReg(RA8876_REG_GTFNT_SEL, (chip & 0x07) << 5);

  SPI.endTransaction();
}

void RA8876::selectExternalFont(enum ExternalFontFamily family, enum FontSize size, enum FontEncoding enc, FontFlags flags)
{
  m_fontSource = RA8876_FONT_SOURCE_EXT_ROM;
  m_fontSize   = size;
  m_fontFlags  = flags;

  SPI.beginTransaction(m_spiSettings);

  if (deBug & 0x4) {
    Serial.print("CCR0: ");
    Serial.println(0x40 | ((size & 0x03) << 4), HEX);
  }
  writeReg(RA8876_REG_CCR0, 0x40 | ((size & 0x03) << 4));  // Select external font ROM and size

  uint8_t ccr1 = readReg(RA8876_REG_CCR1);
#ifdef TRANSPARENT
  if ((ccr1 & 0x40) == 0) {
    ccr1 |= 0x40;  // Transparent background
    writeReg(RA8876_REG_CCR1, ccr1);
  }
#else
  if (ccr1 & 0x40) {
    ccr1 &= ~0x40;  // no Transparent background
    writeReg(RA8876_REG_CCR1, ccr1);
  }
#endif
  if (deBug & 0x4) {
    Serial.print("CCR1: ");
    Serial.println(ccr1, HEX);
  }

  if (deBug & 0x4) {
    Serial.print("GTFNT_CR: ");
    Serial.println((enc << 3) | (family & 0x03), HEX);
  }
  writeReg(RA8876_REG_GTFNT_CR, (enc << 3) | (family & 0x03));  // Character encoding and family

  SPI.endTransaction();
}

pd0lew · Apr 20, 2025

Thank you for the reply, but how to use this in my Arduino code .... perhaps a stupid question...

pd0lew · Apr 21, 2025

I think we must redo keywords text for the RA8876 because a lot of things are not there when I look in source files.
This is confusing so I will make a new keywords file special for the RA8876 display.

My RTTY modem works awesome on a RA8876 display.
Here the very basic setup to get something to work without hassels.

Code:

// Test program for RA8876
#include <SPI.h>
#include <Wire.h>
#include <FT5206.h>
#include "RA8876_t3.h"
#include "USBHost_t36.h"
// Please use  ILI9341_fonts-master
#include "font_LiberationMono.h"
#define SCREEN_WIDTH 1024
#define SCREEN_HEIGHT 600
#define RA8876_CS 10
#define RA8876_RESET 255
// Backlite connect pin 14 (RA8876) to 3.3V or use an ouput from Teensy PWM
RA8876_t3 tft = RA8876_t3(RA8876_CS, RA8876_RESET);
#define CTP_INT 6

uint8_t registers[FT5206_REGISTERS];
uint16_t new_coordinates[1][2];
uint8_t current_touches = 0;
uint16_t TouchX, TouchY, TouchZ;
FT5206 cts = FT5206(CTP_INT);
bool flag_touch = false;

void setup() {
  cts.begin();
  tft.begin(30000000);
  tft.fillScreen(BLACK);
  tft.setCursor(340, 300);
  tft.setFont(LiberationMono_28);
  tft.setTextColor(YELLOW);
  tft.print(" Welcome to PJRC");
 
}

void loop() {

  if (cts.touched()) {
    cts.getTSregisters(registers);
    current_touches = cts.getTScoordinates(new_coordinates, registers);
    TouchX = SCREEN_WIDTH - new_coordinates[0][0];
    TouchY = SCREEN_HEIGHT - new_coordinates[0][1];
    TouchZ = current_touches;
    cts.rearmISR();
  }
  if (TouchZ && !flag_touch) {
    flag_touch = true;
    tft.fillScreen(BLACK);
    tft.setFont(LiberationMono_28);
    tft.setTextColor(WHITE, BLACK);
    tft.setCursor(220, 300);
    tft.println(" Touchscreen is working ");
  }
}

pd0lew · Apr 22, 2025

Hi group,

Is there anyone who can help with the font rom for my RTTY decoder. The thing is when using LiberationMono font and use 9 lines of text and when shifting up it not looks very nice that can better. There is simply to much delay, with the font rom we can avoid that problem and shifting very fast the lines up.

Please help!

Best,

Johan

MorganS · Apr 22, 2025

"Shifting it up"? Use a scroll window or BTE function. If you're really stuck on a custom font then write the special characters to another layer and just copy layer-to-layer. Layers are actually more useful when used for their original purpose: spend time writing to a hidden layer then promote that to be visible only when you're finished.

pd0lew · Apr 22, 2025

Unfortunately layers are not supported in this library, I used layers a lot in the RA8875 but in the the lite version I can not find anything about layers.

Best,
Johan

MorganS · Apr 22, 2025

Sorry, I was thinking of the "5" not the "6". You are correct that they are not the same thing. The "6" has pages but they're not as good as layers.
But you still have a scroll function.

pd0lew · Apr 23, 2025

It's also not a 6" but a 7" here I show you what I mean ... this can be a bit better.

Best regards,

Johan

MorganS · Apr 23, 2025

Did you try the scroll function?
What SPI frequency did you use? I seem to remember this can go to 80MHz so long as your wiring isn't completely terrible.

dundakitty · Apr 24, 2025

Looks like the Lite library uses genitopCharacterRomParameter() to select the external font ROM. Something like:

Code:

genitopCharacterRomParameter(RA8876_SERIAL_FLASH_SELECT1,RA8876_SPI_DIV4,RA8876_GT30L32S4W,
                      RA8876_ASCII, RA8876_GT_VARIABLE_WIDTH_ARIAL);

or

Code:

genitopCharacterRomParameter(RA8876_SERIAL_FLASH_SELECT1,RA8876_SPI_DIV4,RA8876_GT30L32S4W,
                      RA8876_ASCII, RA8876_GT_VARIABLE_FIXED_WIDTH_ROMAN);

RA8876LiteTeensy For Teensy T36 and T40

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