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//go:build avr && atmega
package runtime
import (
"device/avr"
"machine"
)
func initUART() {
machine.InitSerial()
}
func putchar(c byte) {
machine.Serial.WriteByte(c)
}
func getchar() byte {
for machine.Serial.Buffered() == 0 {
Gosched()
}
v, _ := machine.Serial.ReadByte()
return v
}
func buffered() int {
return machine.Serial.Buffered()
}
// Sleep for a given period. The period is defined by the WDT peripheral, and is
// on most chips (at least) 3 bits wide, in powers of two from 16ms to 2s
// (0=16ms, 1=32ms, 2=64ms...). Note that the WDT is not very accurate: it can
// be off by a large margin depending on temperature and supply voltage.
//
// TODO: disable more peripherals etc. to reduce sleep current.
func sleepWDT(period uint8) {
// Configure WDT
avr.Asm("cli")
avr.Asm("wdr")
// Start timed sequence.
avr.WDTCSR.SetBits(avr.WDTCSR_WDCE | avr.WDTCSR_WDE)
// Enable WDT and set new timeout
avr.WDTCSR.SetBits(avr.WDTCSR_WDIE | period)
avr.Asm("sei")
// Set sleep mode to idle and enable sleep mode.
// Note: when using something other than idle, the UART won't work
// correctly. This needs to be fixed, though, so we can truly sleep.
avr.SMCR.Set((0 << 1) | avr.SMCR_SE)
// go to sleep
avr.Asm("sleep")
// disable sleep
avr.SMCR.Set(0)
}
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