67 lines
1.8 KiB
Arduino
67 lines
1.8 KiB
Arduino
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/**
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* mega-blink-test.ino
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*
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* Arduino Mega 2560 GPIO test sketch used by mega-emulation.test.ts
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*
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* Exercises pins across multiple ATmega2560 ports:
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* - Pin 13 — PORTB bit 7 (LED_BUILTIN)
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* - Pins 22-29 — PORTA bits 0-7 (all HIGH in setup)
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* - Pin 53 — PORTB bit 0 (SPI SS)
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* - Pin 4 — PORTG bit 5
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* - Pin 6 — PORTH bit 3 (PWM)
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* - Pin 42 — PORTL bit 7
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*
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* loop(): blinks pin 13 using a busy-wait loop (avoids Timer0 ISR dependency)
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* so the emulation test can detect both HIGH→LOW and LOW→HIGH transitions
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* within a bounded cycle budget.
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*
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* NOTE: delay() is intentionally avoided here. Arduino's delay() relies on
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* Timer0 overflow interrupts whose vector address differs between ATmega328P
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* (used by avr8js defaults) and ATmega2560, so it would spin forever in the
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* emulator. The busy-wait loop below completes in ~1.4 M CPU cycles per half-
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* period — well within the 20 M cycle budget of the emulation test.
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*/
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/* Number of iterations per half-blink; ~14 cycles/iter × 100 000 ≈ 1.4 M cycles */
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#define HALF_BLINK_ITERS 100000UL
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static void busyWait(unsigned long iters) {
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volatile unsigned long i;
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for (i = 0; i < iters; i++) { /* nothing */ }
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}
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void setup() {
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// LED_BUILTIN = pin 13 = PORTB bit 7
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pinMode(13, OUTPUT);
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digitalWrite(13, HIGH);
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// PORTA: pins 22–29 (bits 0–7)
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for (int i = 22; i <= 29; i++) {
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pinMode(i, OUTPUT);
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digitalWrite(i, HIGH);
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}
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// PORTB bit 0: pin 53 (SPI SS)
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pinMode(53, OUTPUT);
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digitalWrite(53, HIGH);
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// PORTG bit 5: pin 4
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pinMode(4, OUTPUT);
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digitalWrite(4, HIGH);
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// PORTH bit 3: pin 6
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pinMode(6, OUTPUT);
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digitalWrite(6, HIGH);
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// PORTL bit 7: pin 42
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pinMode(42, OUTPUT);
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digitalWrite(42, HIGH);
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}
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void loop() {
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digitalWrite(13, HIGH);
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busyWait(HALF_BLINK_ITERS);
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digitalWrite(13, LOW);
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busyWait(HALF_BLINK_ITERS);
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}
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