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twiboot
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Calculate timer values

This commit is contained in:
Olaf Rempel 2020-01-20 23:41:18 +01:00
parent 1ff13ca69e
commit 7e7e50ad84
1 changed files with 8 additions and 7 deletions
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15
main.c
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@ -25,11 +25,13 @@
#define EEPROM_SUPPORT 1 #define EEPROM_SUPPORT 1
#define LED_SUPPORT 1 #define LED_SUPPORT 1
/* 25ms @8MHz */ #define F_CPU 8000000ULL
#define TIMER_RELOAD (0xFF - 195) #define TIMER_DIVISOR 1024
#define TIMER_IRQFREQ_MS 25
#define TIMEOUT_MS 1000
/* 40 * 25ms */ #define TIMER_MSEC2TICKS(x) ((x * F_CPU) / (TIMER_DIVISOR * 1000ULL))
#define TIMEOUT 40 #define TIMER_MSEC2IRQCNT(x) (x / TIMER_IRQFREQ_MS)
#if LED_SUPPORT #if LED_SUPPORT
#define LED_INIT() DDRB = ((1<<PORTB4) | (1<<PORTB5)) #define LED_INIT() DDRB = ((1<<PORTB4) | (1<<PORTB5))
@ -130,8 +132,7 @@ const static uint8_t chipinfo[8] = {
#endif #endif
}; };
/* wait 40 * 25ms = 1s */ static uint8_t boot_timeout = TIMER_MSEC2IRQCNT(TIMEOUT_MS);
static uint8_t boot_timeout = TIMEOUT;
static uint8_t cmd = CMD_WAIT; static uint8_t cmd = CMD_WAIT;
/* flash buffer */ /* flash buffer */
@ -413,7 +414,7 @@ static void TWI_vect(void)
static void TIMER0_OVF_vect(void) static void TIMER0_OVF_vect(void)
{ {
/* restart timer */ /* restart timer */
TCNT0 = TIMER_RELOAD; TCNT0 = 0xFF - TIMER_MSEC2TICKS(TIMER_IRQFREQ_MS);
/* blink LED while running */ /* blink LED while running */
LED_GN_TOGGLE(); LED_GN_TOGGLE();