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avr: initial implementation for PWM

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Signed-off-by: Ron Evans <ron@hybridgroup.com>

Edited slightly by Ayke van Laethem
This commit is contained in:
Ron Evans
2018-09-14 14:42:47 +02:00
committed by Ayke van Laethem
parent 94358959f5
commit fc0ff3a987
5 changed files with 142 additions and 6 deletions
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src/machine/machine.go
+4
View File
@@ -15,3 +15,7 @@ func (p GPIO) High() {
func (p GPIO) Low() {
p.Set(false)
}
type PWM struct {
Pin uint8
}
src/machine/machine_avr.go
+66
View File
@@ -58,3 +58,69 @@ func (p GPIO) Get() bool {
return (val > 0)
}
}
// InitPWM initializes the registers needed for PWM.
func InitPWM() {
// use waveform generation
*avr.TCCR0A |= avr.TCCR0A_WGM00
// set timer 0 prescale factor to 64
*avr.TCCR0B |= avr.TCCR0B_CS01 | avr.TCCR0B_CS00
// set timer 1 prescale factor to 64
*avr.TCCR1B |= avr.TCCR1B_CS11
// put timer 1 in 8-bit phase correct pwm mode
*avr.TCCR1A |= avr.TCCR1A_WGM10
// set timer 2 prescale factor to 64
*avr.TCCR2B |= avr.TCCR2B_CS22
// configure timer 2 for phase correct pwm (8-bit)
*avr.TCCR2A |= avr.TCCR2A_WGM20
}
// Configure configures a PWM pin for output.
func (pwm PWM) Configure() {
if pwm.Pin < 8 {
*avr.DDRD |= 1 << pwm.Pin
} else {
*avr.DDRB |= 1 << (pwm.Pin - 8)
}
}
// Set turns on the duty cycle for a PWM pin using the provided value. On the AVR this is normally a
// 8-bit value ranging from 0 to 255.
func (pwm PWM) Set(value uint16) {
value8 := value >> 8
switch pwm.Pin {
case 3:
// connect pwm to pin on timer 2, channel B
*avr.TCCR2A |= avr.TCCR2A_COM2B1
*avr.OCR2B = avr.RegValue(value8) // set pwm duty
case 5:
// connect pwm to pin on timer 0, channel B
*avr.TCCR0A |= avr.TCCR0A_COM0B1
*avr.OCR0B = avr.RegValue(value8) // set pwm duty
case 6:
// connect pwm to pin on timer 0, channel A
*avr.TCCR0A |= avr.TCCR0A_COM0A1
*avr.OCR0A = avr.RegValue(value8) // set pwm duty
case 9:
// connect pwm to pin on timer 1, channel A
*avr.TCCR1A |= avr.TCCR1A_COM1A1
// this is a 16-bit value, but we only currently allow the low order bits to be set
*avr.OCR1AL = avr.RegValue(value8) // set pwm duty
case 10:
// connect pwm to pin on timer 1, channel B
*avr.TCCR1A |= avr.TCCR1A_COM1B1
// this is a 16-bit value, but we only currently allow the low order bits to be set
*avr.OCR1BL = avr.RegValue(value8) // set pwm duty
case 11:
// connect pwm to pin on timer 2, channel A
*avr.TCCR2A |= avr.TCCR2A_COM2A1
*avr.OCR2A = avr.RegValue(value8) // set pwm duty
default:
panic("Invalid PWM pin")
}
}