STM32 chaser

// Chaser: a dot sweeping back and forth along six LEDs.
//
// One GPIO per lamp: PA1 to PA6, in order along the Black Pill's left header.
// No shift register, no timer, just six pinMode calls and a loop, the same
// circuit as the ESP32-C3 Knight Rider example, wired to a different board.
//
// The sweep turns round one short of each end, so the two end lamps light
// once a pass and the middle ones twice.

const int LAMPS[] = {PA1, PA2, PA3, PA4, PA5, PA6};
const int COUNT = 6;
const int STEP_MS = 90;

static void show(int lit) {
  for (int i = 0; i < COUNT; i++) {
    digitalWrite(LAMPS[i], i == lit ? HIGH : LOW);
  }
}

void setup() {
  for (int i = 0; i < COUNT; i++) {
    pinMode(LAMPS[i], OUTPUT);
    digitalWrite(LAMPS[i], LOW);
  }
  Serial.begin(115200);
  Serial.println("Mokxi STM32F411: six lamps, one dot");
}

void loop() {
  for (int i = 0; i < COUNT; i++) {
    show(i);
    delay(STEP_MS);
  }
  for (int i = COUNT - 2; i > 0; i--) {
    show(i);
    delay(STEP_MS);
  }
}