59 lines
1.1 KiB
C++
59 lines
1.1 KiB
C++
#define resolution 8
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#define mains 50 // 60: north america, japan; 50: most other places
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#define refresh 2 * 1000000 / mains
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// Counter for the timer
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extern volatile unsigned long timer0_overflow_count;
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/* === */
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/* ??? */
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void startTimer() {
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timer0_overflow_count = 0;
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TCNT0 = 0;
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}
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unsigned long checkTimer() {
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return ((timer0_overflow_count << 8) + TCNT0) << 2;
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}
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long time(int pin, byte mask) {
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unsigned long count = 0, total = 0;
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while(checkTimer() < refresh) {
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// pinMode is about 6 times slower than assigning
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// DDRB directly, but that pause is important
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pinMode(pin, OUTPUT);
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PORTB = 0;
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pinMode(pin, INPUT);
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while((PINB & mask) == 0)
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count++;
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total++;
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}
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startTimer();
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return (count << resolution) / total;
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}
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/* ??? */
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/* === */
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void setup() {
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// Initialize serial communication
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Serial.begin(115200);
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// INPUT on pin 8
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pinMode(8, INPUT);
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// Start timer
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startTimer();
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}
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void loop() {
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// Print output to serial in decimal
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Serial.print(time(8, B00000001), DEC);
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Serial.print(" ");
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}
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