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Merged
deadprogram merged 2 commits into from
Mar 24, 2026
+56 −28
Merged

machine/stm32: fix PWM problem due to register shifting #5256

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d669d02
machine/stm32: fix PWM problem due to register shifting.
deadprogram Mar 18, 2026
f6ac807
target: add PWM constant values for Arduino UNO Q
deadprogram Mar 18, 2026
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11 changes: 11 additions & 0 deletions src/examples/pwm/arduino-uno-q.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
//go:build arduino_uno_q

package main

import "machine"

var (
pwm = &machine.TIM3
pinA = machine.D3 // PB0 = TIM3_CH3
pinB = machine.D6 // PB1 = TIM3_CH4
)
26 changes: 13 additions & 13 deletions src/machine/board_arduino_uno_q.go
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Original file line number Diff line number Diff line change
Expand Up @@ -27,24 +27,24 @@ const (
ADC4 = A4
ADC5 = A5

D0 = PB7
D1 = PB6
D2 = PB3
D3 = PB0
D0 = PB7 // USART1 RX, PWM TIM4_CH2
D1 = PB6 // USART1 TX, PWM TIM4_CH1
D2 = PB3 // PWM TIM2_CH2
D3 = PB0 // PWM TIM3_CH3
D4 = PA12
D5 = PA11
D6 = PB1
D5 = PA11 // PWM TIM1_CH4
D6 = PB1 // PWM TIM3_CH4
D7 = PB2
D8 = PB4
D9 = PB8
D10 = PB9
D11 = PB15
D12 = PB14
D8 = PB4 // PWM TIM3_CH1
D9 = PB8 // PWM TIM4_CH3 / TIM16_CH1
D10 = PB9 // PWM TIM4_CH4 / TIM17_CH1
D11 = PB15 // PWM TIM15_CH2
D12 = PB14 // PWM TIM15_CH1
D13 = PB13
D18 = PC1
D19 = PC0
D20 = PB10
D21 = PB11
D20 = PB10 // I2C2 SCL, PWM TIM2_CH3
D21 = PB11 // I2C2 SDA, PWM TIM2_CH4
)

const (
Expand Down
47 changes: 32 additions & 15 deletions src/machine/machine_stm32_tim.go
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Expand Up @@ -13,6 +13,23 @@ import (

const PWM_MODE1 = 0x6

// Hardware bit positions for TIM registers. The SVD-generated constants
// (stm32.TIM_CCMR1_Output_OC1M_Pos, stm32.TIM_CCER_CC1E, etc.) are
// systematically shifted by one channel in some STM32 device files,
// so we define the correct hardware positions here.
const (
// OC1M[2:0] field position within each CCMR half (bits [6:4]).
tim_CCMR_OCxM_Pos = 4

// Per-channel bit positions within CCER (4 bits per channel).
tim_CCER_CCxE = 0x1 // CCxE at bit 0 of channel group
tim_CCER_CCxP = 0x2 // CCxP at bit 1 of channel group

// Per-channel bit positions within SR, EGR, and DIER (1 bit per channel,
// starting at bit 1 for CC1). Use as: tim_CC1_bit << channel.
tim_CC1_bit = 0x2 // CC1G/CC1IF/CC1IE at bit 1
)

type TimerCallback func()
type ChannelCallback func(channel uint8)

Expand Down Expand Up @@ -99,14 +116,14 @@ func (t *TIM) SetMatchInterrupt(channel uint8, callback ChannelCallback) error {
t.OCInterrupt = t.registerOCInterrupt()

// Clear the interrupt flag
t.Device.SR.ClearBits(stm32.TIM_SR_CC1IF << channel)
t.Device.SR.ClearBits(tim_CC1_bit << channel)

// Enable the interrupt
t.OCInterrupt.SetPriority(0xc1)
t.OCInterrupt.Enable()

// Enable the hardware interrupt
t.Device.DIER.SetBits(stm32.TIM_DIER_CC1IE << channel)
t.Device.DIER.SetBits(tim_CC1_bit << channel)

return nil
}
Expand Down Expand Up @@ -210,20 +227,20 @@ func (t *TIM) Set(channel uint8, value uint32) {
// Set the PWM to Mode 1 (active below set value, inactive above)
// Preload is disabled so we can change OC value within one update period.
var ccmrVal uint32
ccmrVal |= PWM_MODE1 << stm32.TIM_CCMR1_Output_OC1M_Pos
ccmrVal |= PWM_MODE1 << tim_CCMR_OCxM_Pos
ccmr.ReplaceBits(ccmrVal, 0xFF, offset)

// Set the compare value
ccr.Set(arrtype(value))

// Enable the channel (if not already)
t.Device.CCER.ReplaceBits(stm32.TIM_CCER_CC1E, 0xD, channel*4)
t.Device.CCER.ReplaceBits(tim_CCER_CCxE, 0xD, channel*4)

// Force update
t.Device.EGR.SetBits(stm32.TIM_EGR_CC1G << channel)
t.Device.EGR.SetBits(tim_CC1_bit << channel)

// Reset Interrupt Flag
t.Device.SR.ClearBits(stm32.TIM_SR_CC1IF << channel)
t.Device.SR.ClearBits(tim_CC1_bit << channel)

// Restore interrupts
interrupt.Restore(mask)
Expand All @@ -242,10 +259,10 @@ func (t *TIM) Unset(channel uint8) {
ccr.Set(0)

// Disable the hardware interrupt
t.Device.DIER.ClearBits(stm32.TIM_DIER_CC1IE << channel)
t.Device.DIER.ClearBits(tim_CC1_bit << channel)

// Clear the interrupt flag
t.Device.SR.ClearBits(stm32.TIM_SR_CC1IF << channel)
t.Device.SR.ClearBits(tim_CC1_bit << channel)

// Restore interrupts
interrupt.Restore(mask)
Expand All @@ -261,10 +278,10 @@ func (t *TIM) SetInverting(channel uint8, inverting bool) {

var val = uint32(0)
if inverting {
val |= stm32.TIM_CCER_CC1P
val |= tim_CCER_CCxP
}

t.Device.CCER.ReplaceBits(val, stm32.TIM_CCER_CC1P_Msk, channel*4)
t.Device.CCER.ReplaceBits(val, tim_CCER_CCxP, channel*4)
}

func (t *TIM) handleUPInterrupt(interrupt.Interrupt) {
Expand All @@ -279,29 +296,29 @@ func (t *TIM) handleUPInterrupt(interrupt.Interrupt) {
}

func (t *TIM) handleOCInterrupt(interrupt.Interrupt) {
if t.Device.SR.HasBits(stm32.TIM_SR_CC1IF) {
if t.Device.SR.HasBits(tim_CC1_bit << 0) {
if t.channelCallbacks[0] != nil {
t.channelCallbacks[0](0)
}
}
if t.Device.SR.HasBits(stm32.TIM_SR_CC2IF) {
if t.Device.SR.HasBits(tim_CC1_bit << 1) {
if t.channelCallbacks[1] != nil {
t.channelCallbacks[1](1)
}
}
if t.Device.SR.HasBits(stm32.TIM_SR_CC3IF) {
if t.Device.SR.HasBits(tim_CC1_bit << 2) {
if t.channelCallbacks[2] != nil {
t.channelCallbacks[2](2)
}
}
if t.Device.SR.HasBits(stm32.TIM_SR_CC4IF) {
if t.Device.SR.HasBits(tim_CC1_bit << 3) {
if t.channelCallbacks[3] != nil {
t.channelCallbacks[3](3)
}
}

// Reset interrupt flags
t.Device.SR.ClearBits(stm32.TIM_SR_CC1IF | stm32.TIM_SR_CC2IF | stm32.TIM_SR_CC3IF | stm32.TIM_SR_CC4IF)
t.Device.SR.ClearBits(tim_CC1_bit<<0 | tim_CC1_bit<<1 | tim_CC1_bit<<2 | tim_CC1_bit<<3)
}

func (t *TIM) channelCCR(channel uint8) *arrRegType {
Expand Down
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