johnwasser:
Very strange. I put in a 500 millisecond delay and the outputs only come out every 5 seconds. WTF?At what rate did you want the interrupts? 4 KHz?
I notice you clear some bits in TCCR1A but leave the other bits unchanged. How do you assure that the other bits are already set as you desire?
Sorry about that--that comment and a couple of others were relics of old code that I missed when trimming. The other bits in those registered are initialized to zero, according to the Atmel docs, so in actuality, I don't need to manually clear anything at all. Here's an update:
#include <stdint.h>
#include <avr/interrupt.h>
#include <avr/io.h>
volatile static unsigned long init_counter = 0;
void setup() {
// Disable global interrupts
cli();
// Setup Timer/Counter1 Control Registers (TCCR1) with the following options:
// Timer/Counter Mode of Operation | CTC
// TOP | OCR1A
// Update of OCR1x at | Immediate
// TOV1 Flag Set on | MAX
TCCR1B |= _BV(WGM12); // Clear bit WGM13 and set bit WGM12 in TCCR1B
TCCR1B |= _BV(CS11); // Setup clock prescaler for TCCR1 as clk_IO/8
unsigned long ocr1a_divisor = (unsigned long) 8 * 100 * 100;
OCR1A = F_CPU / ocr1a_divisor;
// Enable Timer/Counter1 Output Compare A Match Interrupt
TIMSK1 |= _BV(OCIE1A);
// Re-enable global interrupts
sei();
Serial.begin(9600);
}
void loop() {
while(true) {
Serial.println(init_counter);
}
}
ISR(TIMER1_COMPA_vect) {
if (init_counter < 50000)
init_counter++;
}
With the I/O clock running at 16MHz, OCR1A is set to 200. So, that ISR should be firing at 10kHz. (Please feel free to correct my calculation if it's wrong.) Where were you putting the delay?