I want to put the mcu to deep-sleep and then wake it up some time later.
The datasheet says the clock source can be the RTC crystal, which is 32.768kHz, so I would expect that the symbol counter counted at that speed. This would mean I'd have 2 seconds every 2^16bits in the counter, but instead I'm getting ~1s.
According to this post, every 2^16bits in symbol counter is one second, now why?
I thought the symbol counter would count at the RTC frequency, doesn't it?
On section 10.2 on the datasheet, it says
Quote:
Note: The AVR system clock has to be at least 4 times the symbol counter clock
frequency. The symbol counter clock frequency is usually 62.5kHz, which would require
a minimum of 250kHz AVR system clock frequency
That 'usually' doesn't satisfy me, since that means that sometimes the clock isn't running at that speed, so, how could I control for how long the mcu goes to sleep if I don't know the frequency of the counter.
Anybody knows?
My code:
#include#include #include #include uint8_t temp; ISR(SCNT_CMP1_vect) { } int main(void) { temp = MCUSR; MCUSR = 0; wdt_disable(); serial_init(); //Debug only SCCR0 = (1<<SCEN) | (1<<SCCKSEL); TRXPR |= (1<<SLPTR); #define SLEEP_IDLE 0x00 #define SLEEP_POWER_DOWN 0x02 #define SLEEP_POWER_SAVE 0x03 ASSR |= (1<<AS2); SCOCR1HH = 0x00; SCOCR1HL = 0x28; //this gives around 42s SCOCR1LH = 0x00; SCOCR1LL = 0x00; SCCNTHH = 0; SCCNTHL = 0; SCCNTLH = 0; SCCNTLL = 0; while(SCSR & (1<<SCBSY)); SCIRQM |= (1<<IRQMCP1); printf("\n\tEntra a Deep-Sleep\n"); sei(); SMCR_struct.sm = SLEEP_POWER_SAVE; SMCR_struct.se = 1; asm("sleep"); SMCR_struct.sm = SLEEP_IDLE; SMCR_struct.se = 0; temp = SCCNTLL; while(1) { } }
