diff options
Diffstat (limited to 'src/machine/machine_atmega328.go')
| -rw-r--r-- | src/machine/machine_atmega328.go | 548 |
1 files changed, 548 insertions, 0 deletions
diff --git a/src/machine/machine_atmega328.go b/src/machine/machine_atmega328.go new file mode 100644 index 000000000..e4b2bb06f --- /dev/null +++ b/src/machine/machine_atmega328.go @@ -0,0 +1,548 @@ +//go:build avr && (atmega328p || atmega328pb) + +package machine + +import ( + "device/avr" + "runtime/interrupt" + "runtime/volatile" +) + +// PWM is one PWM peripheral, which consists of a counter and two output +// channels (that can be connected to two fixed pins). You can set the frequency +// using SetPeriod, but only for all the channels in this PWM peripheral at +// once. +type PWM struct { + num uint8 +} + +var ( + Timer0 = PWM{0} // 8 bit timer for PD5 and PD6 + Timer1 = PWM{1} // 16 bit timer for PB1 and PB2 + Timer2 = PWM{2} // 8 bit timer for PB3 and PD3 +) + +// Configure enables and configures this PWM. +// +// For the two 8 bit timers, there is only a limited number of periods +// available, namely the CPU frequency divided by 256 and again divided by 1, 8, +// 64, 256, or 1024. For a MCU running at 16MHz, this would be a period of 16µs, +// 128µs, 1024µs, 4096µs, or 16384µs. +func (pwm PWM) Configure(config PWMConfig) error { + switch pwm.num { + case 0, 2: // 8-bit timers (Timer/counter 0 and Timer/counter 2) + // Calculate the timer prescaler. + // While we could configure a flexible top, that would sacrifice one of + // the PWM output compare registers and thus a PWM channel. I've chosen + // to instead limit this timer to a fixed number of frequencies. + var prescaler uint8 + switch config.Period { + case 0, (uint64(1e9) * 256 * 1) / uint64(CPUFrequency()): + prescaler = 1 + case (uint64(1e9) * 256 * 8) / uint64(CPUFrequency()): + prescaler = 2 + case (uint64(1e9) * 256 * 64) / uint64(CPUFrequency()): + prescaler = 3 + case (uint64(1e9) * 256 * 256) / uint64(CPUFrequency()): + prescaler = 4 + case (uint64(1e9) * 256 * 1024) / uint64(CPUFrequency()): + prescaler = 5 + default: + return ErrPWMPeriodTooLong + } + + if pwm.num == 0 { + avr.TCCR0B.Set(prescaler) + // Set the PWM mode to fast PWM (mode = 3). + avr.TCCR0A.Set(avr.TCCR0A_WGM00 | avr.TCCR0A_WGM01) + // monotonic timer is using the same time as PWM:0 + // we must adust internal settings of monotonic timer when PWM:0 settings changed + adjustMonotonicTimer() + } else { + avr.TCCR2B.Set(prescaler) + // Set the PWM mode to fast PWM (mode = 3). + avr.TCCR2A.Set(avr.TCCR2A_WGM20 | avr.TCCR2A_WGM21) + } + case 1: // Timer/counter 1 + // The top value is the number of PWM ticks a PWM period takes. It is + // initially picked assuming an unlimited counter top and no PWM + // prescaler. + var top uint64 + if config.Period == 0 { + // Use a top appropriate for LEDs. Picking a relatively low period + // here (0xff) for consistency with the other timers. + top = 0xff + } else { + // The formula below calculates the following formula, optimized: + // top = period * (CPUFrequency() / 1e9) + // By dividing the CPU frequency first (an operation that is easily + // optimized away) the period has less chance of overflowing. + top = config.Period * (uint64(CPUFrequency()) / 1000000) / 1000 + } + + avr.TCCR1A.Set(avr.TCCR1A_WGM11) + + // The ideal PWM period may be larger than would fit in the PWM counter, + // which is 16 bits (see maxTop). Therefore, try to make the PWM clock + // speed lower with a prescaler to make the top value fit the maximum + // top value. + const maxTop = 0x10000 + switch { + case top <= maxTop: + avr.TCCR1B.Set(3<<3 | 1) // no prescaling + case top/8 <= maxTop: + avr.TCCR1B.Set(3<<3 | 2) // divide by 8 + top /= 8 + case top/64 <= maxTop: + avr.TCCR1B.Set(3<<3 | 3) // divide by 64 + top /= 64 + case top/256 <= maxTop: + avr.TCCR1B.Set(3<<3 | 4) // divide by 256 + top /= 256 + case top/1024 <= maxTop: + avr.TCCR1B.Set(3<<3 | 5) // divide by 1024 + top /= 1024 + default: + return ErrPWMPeriodTooLong + } + + // A top of 0x10000 is at 100% duty cycle. Subtract one because the + // counter counts from 0, not 1 (avoiding an off-by-one). + top -= 1 + + avr.ICR1H.Set(uint8(top >> 8)) + avr.ICR1L.Set(uint8(top)) + } + return nil +} + +// SetPeriod updates the period of this PWM peripheral. +// To set a particular frequency, use the following formula: +// +// period = 1e9 / frequency +// +// If you use a period of 0, a period that works well for LEDs will be picked. +// +// SetPeriod will not change the prescaler, but also won't change the current +// value in any of the channels. This means that you may need to update the +// value for the particular channel. +// +// Note that you cannot pick any arbitrary period after the PWM peripheral has +// been configured. If you want to switch between frequencies, pick the lowest +// frequency (longest period) once when calling Configure and adjust the +// frequency here as needed. +func (pwm PWM) SetPeriod(period uint64) error { + if pwm.num != 1 { + return ErrPWMPeriodTooLong // TODO better error message + } + + // The top value is the number of PWM ticks a PWM period takes. It is + // initially picked assuming an unlimited counter top and no PWM + // prescaler. + var top uint64 + if period == 0 { + // Use a top appropriate for LEDs. Picking a relatively low period + // here (0xff) for consistency with the other timers. + top = 0xff + } else { + // The formula below calculates the following formula, optimized: + // top = period * (CPUFrequency() / 1e9) + // By dividing the CPU frequency first (an operation that is easily + // optimized away) the period has less chance of overflowing. + top = period * (uint64(CPUFrequency()) / 1000000) / 1000 + } + + prescaler := avr.TCCR1B.Get() & 0x7 + switch prescaler { + case 1: + top /= 1 + case 2: + top /= 8 + case 3: + top /= 64 + case 4: + top /= 256 + case 5: + top /= 1024 + } + + // A top of 0x10000 is at 100% duty cycle. Subtract one because the counter + // counts from 0, not 1 (avoiding an off-by-one). + top -= 1 + + if top > 0xffff { + return ErrPWMPeriodTooLong + } + + // Warning: this change is not atomic! + avr.ICR1H.Set(uint8(top >> 8)) + avr.ICR1L.Set(uint8(top)) + + // ... and because of that, set the counter back to zero to avoid most of + // the effects of this non-atomicity. + avr.TCNT1H.Set(0) + avr.TCNT1L.Set(0) + + return nil +} + +// Top returns the current counter top, for use in duty cycle calculation. It +// will only change with a call to Configure or SetPeriod, otherwise it is +// constant. +// +// The value returned here is hardware dependent. In general, it's best to treat +// it as an opaque value that can be divided by some number and passed to Set +// (see Set documentation for more information). +func (pwm PWM) Top() uint32 { + if pwm.num == 1 { + // Timer 1 has a configurable top value. + low := avr.ICR1L.Get() + high := avr.ICR1H.Get() + return uint32(high)<<8 | uint32(low) + 1 + } + // Other timers go from 0 to 0xff (0x100 or 256 in total). + return 256 +} + +// Counter returns the current counter value of the timer in this PWM +// peripheral. It may be useful for debugging. +func (pwm PWM) Counter() uint32 { + switch pwm.num { + case 0: + return uint32(avr.TCNT0.Get()) + case 1: + mask := interrupt.Disable() + low := avr.TCNT1L.Get() + high := avr.TCNT1H.Get() + interrupt.Restore(mask) + return uint32(high)<<8 | uint32(low) + case 2: + return uint32(avr.TCNT2.Get()) + } + // Unknown PWM. + return 0 +} + +// Period returns the used PWM period in nanoseconds. It might deviate slightly +// from the configured period due to rounding. +func (pwm PWM) Period() uint64 { + var prescaler uint8 + switch pwm.num { + case 0: + prescaler = avr.TCCR0B.Get() & 0x7 + case 1: + prescaler = avr.TCCR1B.Get() & 0x7 + case 2: + prescaler = avr.TCCR2B.Get() & 0x7 + } + top := uint64(pwm.Top()) + switch prescaler { + case 1: // prescaler 1 + return 1 * top * 1000 / uint64(CPUFrequency()/1e6) + case 2: // prescaler 8 + return 8 * top * 1000 / uint64(CPUFrequency()/1e6) + case 3: // prescaler 64 + return 64 * top * 1000 / uint64(CPUFrequency()/1e6) + case 4: // prescaler 256 + return 256 * top * 1000 / uint64(CPUFrequency()/1e6) + case 5: // prescaler 1024 + return 1024 * top * 1000 / uint64(CPUFrequency()/1e6) + default: // unknown clock source + return 0 + } +} + +// Channel returns a PWM channel for the given pin. +func (pwm PWM) Channel(pin Pin) (uint8, error) { + pin.Configure(PinConfig{Mode: PinOutput}) + pin.Low() + switch pwm.num { + case 0: + switch pin { + case PD6: // channel A + avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1) + return 0, nil + case PD5: // channel B + avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1) + return 1, nil + } + case 1: + switch pin { + case PB1: // channel A + avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1) + return 0, nil + case PB2: // channel B + avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1) + return 1, nil + } + case 2: + switch pin { + case PB3: // channel A + avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1) + return 0, nil + case PD3: // channel B + avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1) + return 1, nil + } + } + return 0, ErrInvalidOutputPin +} + +// SetInverting sets whether to invert the output of this channel. +// Without inverting, a 25% duty cycle would mean the output is high for 25% of +// the time and low for the rest. Inverting flips the output as if a NOT gate +// was placed at the output, meaning that the output would be 25% low and 75% +// high with a duty cycle of 25%. +// +// Note: the invert state may not be applied on the AVR until the next call to +// ch.Set(). +func (pwm PWM) SetInverting(channel uint8, inverting bool) { + switch pwm.num { + case 0: + switch channel { + case 0: // channel A + if inverting { + avr.PORTB.SetBits(1 << 6) // PB6 high + avr.TCCR0A.SetBits(avr.TCCR0A_COM0A0) + } else { + avr.PORTB.ClearBits(1 << 6) // PB6 low + avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A0) + } + case 1: // channel B + if inverting { + avr.PORTB.SetBits(1 << 5) // PB5 high + avr.TCCR0A.SetBits(avr.TCCR0A_COM0B0) + } else { + avr.PORTB.ClearBits(1 << 5) // PB5 low + avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B0) + } + } + case 1: + // Note: the COM1A0/COM1B0 bit is not set with the configuration below. + // It will be set the following call to Set(), however. + switch channel { + case 0: // channel A, PB1 + if inverting { + avr.PORTB.SetBits(1 << 1) // PB1 high + } else { + avr.PORTB.ClearBits(1 << 1) // PB1 low + } + case 1: // channel B, PB2 + if inverting { + avr.PORTB.SetBits(1 << 2) // PB2 high + } else { + avr.PORTB.ClearBits(1 << 2) // PB2 low + } + } + case 2: + switch channel { + case 0: // channel A + if inverting { + avr.PORTB.SetBits(1 << 3) // PB3 high + avr.TCCR2A.SetBits(avr.TCCR2A_COM2A0) + } else { + avr.PORTB.ClearBits(1 << 3) // PB3 low + avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A0) + } + case 1: // channel B + if inverting { + avr.PORTD.SetBits(1 << 3) // PD3 high + avr.TCCR2A.SetBits(avr.TCCR2A_COM2B0) + } else { + avr.PORTD.ClearBits(1 << 3) // PD3 low + avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B0) + } + } + } +} + +// Set updates the channel value. This is used to control the channel duty +// cycle, in other words the fraction of time the channel output is high (or low +// when inverted). For example, to set it to a 25% duty cycle, use: +// +// pwm.Set(channel, pwm.Top() / 4) +// +// pwm.Set(channel, 0) will set the output to low and pwm.Set(channel, +// pwm.Top()) will set the output to high, assuming the output isn't inverted. +func (pwm PWM) Set(channel uint8, value uint32) { + switch pwm.num { + case 0: + value := uint16(value) + switch channel { + case 0: // channel A + if value == 0 { + avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A1) + } else { + avr.OCR0A.Set(uint8(value - 1)) + avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1) + } + case 1: // channel B + if value == 0 { + avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B1) + } else { + avr.OCR0B.Set(uint8(value) - 1) + avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1) + } + } + // monotonic timer is using the same time as PWM:0 + // we must adust internal settings of monotonic timer when PWM:0 settings changed + adjustMonotonicTimer() + case 1: + mask := interrupt.Disable() + switch channel { + case 0: // channel A, PB1 + if value == 0 { + avr.TCCR1A.ClearBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0) + } else { + value := uint16(value) - 1 // yes, this is safe (it relies on underflow) + avr.OCR1AH.Set(uint8(value >> 8)) + avr.OCR1AL.Set(uint8(value)) + if avr.PORTB.HasBits(1 << 1) { // is PB1 high? + // Yes, set the inverting bit. + avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0) + } else { + // No, output is non-inverting. + avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1) + } + } + case 1: // channel B, PB2 + if value == 0 { + avr.TCCR1A.ClearBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0) + } else { + value := uint16(value) - 1 // yes, this is safe (it relies on underflow) + avr.OCR1BH.Set(uint8(value >> 8)) + avr.OCR1BL.Set(uint8(value)) + if avr.PORTB.HasBits(1 << 2) { // is PB2 high? + // Yes, set the inverting bit. + avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0) + } else { + // No, output is non-inverting. + avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1) + } + } + } + interrupt.Restore(mask) + case 2: + value := uint16(value) + switch channel { + case 0: // channel A + if value == 0 { + avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A1) + } else { + avr.OCR2A.Set(uint8(value - 1)) + avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1) + } + case 1: // channel B + if value == 0 { + avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B1) + } else { + avr.OCR2B.Set(uint8(value - 1)) + avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1) + } + } + } +} + +// Pin Change Interrupts +type PinChange uint8 + +const ( + PinRising PinChange = 1 << iota + PinFalling + PinToggle = PinRising | PinFalling +) + +func (pin Pin) SetInterrupt(pinChange PinChange, callback func(Pin)) (err error) { + + switch { + case pin >= PB0 && pin <= PB7: + // PCMSK0 - PCINT0-7 + pinStates[0] = avr.PINB.Get() + pinIndex := pin - PB0 + if pinChange&PinRising > 0 { + pinCallbacks[0][pinIndex][0] = callback + } + if pinChange&PinFalling > 0 { + pinCallbacks[0][pinIndex][1] = callback + } + if callback != nil { + avr.PCMSK0.SetBits(1 << pinIndex) + } else { + avr.PCMSK0.ClearBits(1 << pinIndex) + } + avr.PCICR.SetBits(avr.PCICR_PCIE0) + interrupt.New(avr.IRQ_PCINT0, handlePCINT0Interrupts) + case pin >= PC0 && pin <= PC7: + // PCMSK1 - PCINT8-14 + pinStates[1] = avr.PINC.Get() + pinIndex := pin - PC0 + if pinChange&PinRising > 0 { + pinCallbacks[1][pinIndex][0] = callback + } + if pinChange&PinFalling > 0 { + pinCallbacks[1][pinIndex][1] = callback + } + if callback != nil { + avr.PCMSK1.SetBits(1 << pinIndex) + } else { + avr.PCMSK1.ClearBits(1 << pinIndex) + } + avr.PCICR.SetBits(avr.PCICR_PCIE1) + interrupt.New(avr.IRQ_PCINT1, handlePCINT1Interrupts) + case pin >= PD0 && pin <= PD7: + // PCMSK2 - PCINT16-23 + pinStates[2] = avr.PIND.Get() + pinIndex := pin - PD0 + if pinChange&PinRising > 0 { + pinCallbacks[2][pinIndex][0] = callback + } + if pinChange&PinFalling > 0 { + pinCallbacks[2][pinIndex][1] = callback + } + if callback != nil { + avr.PCMSK2.SetBits(1 << pinIndex) + } else { + avr.PCMSK2.ClearBits(1 << pinIndex) + } + avr.PCICR.SetBits(avr.PCICR_PCIE2) + interrupt.New(avr.IRQ_PCINT2, handlePCINT2Interrupts) + default: + return ErrInvalidInputPin + } + + return nil +} + +var pinCallbacks [3][8][2]func(Pin) +var pinStates [3]uint8 + +func handlePCINTInterrupts(intr uint8, port *volatile.Register8) { + current := port.Get() + change := pinStates[intr] ^ current + pinStates[intr] = current + for i := uint8(0); i < 8; i++ { + if (change>>i)&0x01 != 0x01 { + continue + } + pin := Pin(intr*8 + i) + value := pin.Get() + if value && pinCallbacks[intr][i][0] != nil { + pinCallbacks[intr][i][0](pin) + } + if !value && pinCallbacks[intr][i][1] != nil { + pinCallbacks[intr][i][1](pin) + } + } +} + +func handlePCINT0Interrupts(intr interrupt.Interrupt) { + handlePCINTInterrupts(0, avr.PINB) +} + +func handlePCINT1Interrupts(intr interrupt.Interrupt) { + handlePCINTInterrupts(1, avr.PINC) +} + +func handlePCINT2Interrupts(intr interrupt.Interrupt) { + handlePCINTInterrupts(2, avr.PIND) +} |