forked from haraldwolff/avr-fw-modules
34 lines
702 B
C
Executable File
34 lines
702 B
C
Executable File
#include <hwo/utils.h>
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#include <avr/io.h>
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#include <avr/wdt.h>
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uint16_t t0_steps[] = { 1,8,64,256,1024 };
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void systick_timer_init(uint32_t systick_us)
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{
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uint64_t clocks = ((uint64_t)systick_us) * ((uint64_t)__freq_cpu) / 1000000LL;
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uint8_t n_prescaler;
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for (n_prescaler = 0; n_prescaler < 5 ; n_prescaler++)
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{
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if ((clocks / t0_steps[ n_prescaler ]) < 256) {
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break;
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};
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};
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if (n_prescaler > 4)
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return;
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n_prescaler++;
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TCCR0A = _BV(WGM01);
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OCR0A = (uint8_t)(clocks / t0_steps[ n_prescaler-1 ]);
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TCCR0B = (n_prescaler & 0x07);
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TIMSK0 |= _BV(OCIE0A);
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//_systick_us = 1000000LL * (1LL << prescale_shift[ n_prescaler ]) * (ocr + 1) / __freq_cpu;
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_systick_us = systick_us;
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};
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