mirror of https://github.com/midilab/uClock
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
62 lines
2.0 KiB
62 lines
2.0 KiB
#include <Arduino.h>
|
|
|
|
#define ATOMIC(X) noInterrupts(); X; interrupts();
|
|
|
|
// want a different avr clock support?
|
|
// TODO: we should do this using macro guards for avrs different clocks freqeuncy setup at compile time
|
|
#define AVR_CLOCK_FREQ 16000000
|
|
|
|
void initTimer(uint32_t init_clock)
|
|
{
|
|
ATOMIC(
|
|
// 16bits Timer1 init
|
|
// begin at 120bpm (48.0007680122882 Hz)
|
|
TCCR1A = 0; // set entire TCCR1A register to 0
|
|
TCCR1B = 0; // same for TCCR1B
|
|
TCNT1 = 0; // initialize counter value to 0
|
|
// set compare match register for 48.0007680122882 Hz increments
|
|
OCR1A = 41665; // = 16000000 / (8 * 48.0007680122882) - 1 (must be <65536)
|
|
// turn on CTC mode
|
|
TCCR1B |= (1 << WGM12);
|
|
// Set CS12, CS11 and CS10 bits for 8 prescaler
|
|
TCCR1B |= (0 << CS12) | (1 << CS11) | (0 << CS10);
|
|
// enable timer compare interrupt
|
|
TIMSK1 |= (1 << OCIE1A);
|
|
)
|
|
}
|
|
|
|
void setTimer(uint32_t us_interval)
|
|
{
|
|
float tick_hertz_interval = 1/((float)us_interval/1000000);
|
|
|
|
uint32_t ocr;
|
|
uint8_t tccr = 0;
|
|
|
|
// 16bits avr timer setup
|
|
if ((ocr = AVR_CLOCK_FREQ / ( tick_hertz_interval * 1 )) < 65535) {
|
|
// Set CS12, CS11 and CS10 bits for 1 prescaler
|
|
tccr |= (0 << CS12) | (0 << CS11) | (1 << CS10);
|
|
} else if ((ocr = AVR_CLOCK_FREQ / ( tick_hertz_interval * 8 )) < 65535) {
|
|
// Set CS12, CS11 and CS10 bits for 8 prescaler
|
|
tccr |= (0 << CS12) | (1 << CS11) | (0 << CS10);
|
|
} else if ((ocr = AVR_CLOCK_FREQ / ( tick_hertz_interval * 64 )) < 65535) {
|
|
// Set CS12, CS11 and CS10 bits for 64 prescaler
|
|
tccr |= (0 << CS12) | (1 << CS11) | (1 << CS10);
|
|
} else if ((ocr = AVR_CLOCK_FREQ / ( tick_hertz_interval * 256 )) < 65535) {
|
|
// Set CS12, CS11 and CS10 bits for 256 prescaler
|
|
tccr |= (1 << CS12) | (0 << CS11) | (0 << CS10);
|
|
} else if ((ocr = AVR_CLOCK_FREQ / ( tick_hertz_interval * 1024 )) < 65535) {
|
|
// Set CS12, CS11 and CS10 bits for 1024 prescaler
|
|
tccr |= (1 << CS12) | (0 << CS11) | (1 << CS10);
|
|
} else {
|
|
// tempo not achiavable
|
|
return;
|
|
}
|
|
|
|
ATOMIC(
|
|
TCCR1B = 0;
|
|
OCR1A = ocr-1;
|
|
TCCR1B |= (1 << WGM12);
|
|
TCCR1B |= tccr;
|
|
)
|
|
} |