Uno R4 · Wire and Qwiic OLEDs

// First-party P5-C acceptance: official Wire/Wire1 drive distinct OLED pixels.
#include <Wire.h>
#include <FspTimer.h>

static FspTimer overlapTimer;
static volatile bool qwiicDone = false;
static volatile uint8_t qwiicStatus = 9;

static uint8_t pattern(TwoWire &bus, bool inverted) {
  static const uint8_t init[] = {
    0xae, 0xd5, 0x80, 0xa8, 0x3f, 0xd3, 0x00, 0x40,
    0x8d, 0x14, 0x20, 0x02, 0xa1, 0xc8, 0xda, 0x12,
    0x81, 0x7f, 0xd9, 0xf1, 0xdb, 0x40, 0xa4, 0xa6, 0x2e, 0xaf
  };
  bus.beginTransmission(0x3c);
  bus.write(0x00);
  bus.write(init, sizeof(init));
  uint8_t status = bus.endTransmission();
  if (status) return status;
  for (uint8_t page = 0; page < 8; ++page) {
    bus.beginTransmission(0x3c);
    bus.write(0x00);
    bus.write(0xb0 | page);
    bus.write(0x00);
    bus.write(0x10);
    status = bus.endTransmission();
    if (status) return status;
    bus.beginTransmission(0x3c);
    bus.write(0x40);
    for (uint8_t x = 0; x < 128; ++x) {
      uint8_t value = ((x / 8 + page) & 1) ? 0xaa : 0x55;
      bus.write(inverted ? (uint8_t)~value : value);
    }
    status = bus.endTransmission();
    if (status) return status;
  }
  return status;
}

static void drawQwiic(timer_callback_args_t *) {
  overlapTimer.stop();
  qwiicStatus = pattern(Wire1, true);
  qwiicDone = true;
}

void setup() {
  Serial.begin(115200);
  Wire.begin();
  Wire1.begin();
  Wire.setClock(400000);
  Wire1.setClock(400000);
  uint8_t timerType = GPT_TIMER;
  int8_t channel = FspTimer::get_available_timer(timerType);
  // A lower-priority GPT callback starts Wire1 while Wire is transmitting.
  // Both official IIC ISR sets can preempt it and continue independently.
  if (channel < 0 || timerType != GPT_TIMER ||
      !overlapTimer.begin(TIMER_MODE_PERIODIC, timerType, channel,
                          (uint32_t)48000, (uint32_t)0, TIMER_SOURCE_DIV_1, drawQwiic) ||
      !overlapTimer.setup_overflow_irq(15) || !overlapTimer.open() || !overlapTimer.start()) {
    Serial.println("timer-error");
    return;
  }
  uint8_t wireStatus = pattern(Wire, false);
  while (!qwiicDone) {}
  Serial.print("wire-pattern ");
  Serial.println(wireStatus);
  Serial.print("qwiic-pattern ");
  Serial.println(qwiicStatus);
  // Two PCF8574s may share this address; their solved input bits combine.
  Wire.beginTransmission(0x20);
  Wire.write(0xff);
  Wire.endTransmission(false);
  uint8_t count = Wire.requestFrom((uint8_t)0x20, (uint8_t)3, (uint8_t)true);
  Serial.print("and-read ");
  Serial.print(count);
  while (Wire.available()) {
    Serial.print(' ');
    Serial.print(Wire.read());
  }
  Serial.println();
  for (uint8_t address = 8; address < 0x78; ++address) {
    Wire.beginTransmission(address);
    Wire.write(0);
    if (!Wire.endTransmission()) {
      Serial.print("found ");
      Serial.println(address);
    }
  }
  Serial.println("scan-done");
}

void loop() {}