can.cpp

#include <ILI9341_t3.h> // https://github.com/PaulStoffregen/ILI9341_t3

struct CanData {
  uint32_t id;
  uint8_t len;
  uint8_t data[8] __attribute__((aligned(8)));
};

int CAN_IDS[] = {
  0x050,
  0x0AE,
  0x0C2,
  0x0D0,
  //...
}
#define CAN_IDS_SIZE (sizeof(CAN_IDS)/sizeof(CAN_IDS[0]))
CanData canData[CAN_IDS_SIZE] = {0};

void init() {
  for (int i = 0; i < CAN_IDS_SIZE; i++) {
    int y = i * 10;
    // initial step, display ids:
    lcdDisplay.setTextSize(1);
    lcdDisplay.setCursor(0, y);
    lcdDisplay.print(canData[i].id, HEX);
  }
}

void loop() {
  static __uint8_t canDataCache[CAN_IDS_SIZE][8] = {0};
  
  // read available CAN messages into canData[] array...
  
  // display data lines:
  for (int i = 0; i < CAN_IDS_SIZE; i++) {
    int y = i * 10;
    const __uint8_t *data = canData[i].data;
    if (memcmp(canDataCache[i], data, 8) == 0)
      continue;
    for (int d = 0; d < 8; d++) {
      if (canDataCache[i][d] == data[d])
        continue;
      int dw = data[d] / 2; // line width, range: 0...128
      lcdDisplay.drawFastHLine(20, y + d, dw, ILI9341_GREEN);
      lcdDisplay.drawFastHLine(20 + dw, y + d, 128 - dw, ILI9341_BLACK);
    }
    memcpy(canDataCache[i], data, 8);
  }
}