STM32F103 Timer alternate function remapping

Question

I am experimenting with some VGA generating code by Artekit, at https://www.artekit.eu/vga-output-using-a-36-pin-stm32/. This code generates a PWM signal for HSYNC using TIM2 Channel 2, which is output on port PA1. This all works correctly. Now I would like to remap TIM2 so that the PWM signal is remapped to pin PB3. After calling GPIO_PinRemapConfig(GPIO_FullRemap_TIM2, ENABLE) the PWM signal no longer appears on PA1 but it does not appear on PB3 although all timer interrupts continue to work as normal. What am I missing?

RCC configuration is as follows:

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_SPI1 | RCC_APB2Periph_TIM1 | RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOC | RCC_APB2Periph_AFIO, ENABLE);

Relevant code is below.

GPIO_InitTypeDef GPIO_InitStructure;
NVIC_InitTypeDef nvic;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
u32 TimerPeriod = 0;
u16 Channel1Pulse = 0, Channel2Pulse = 0, Channel3Pulse = 0;

// Remap PA1 -> PB3
GPIO_PinRemapConfig(GPIO_FullRemap_TIM2, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_Init(GPIOB, &GPIO_InitStructure);

TimerPeriod = 2048;
Channel1Pulse = 144;        /* HSYNC */
Channel2Pulse = 352;         /* HSYNC + BACK PORCH */

TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
TIM_OCInitStructure.TIM_Pulse = Channel1Pulse;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Set;

TIM_OC1Init(TIM1, &TIM_OCInitStructure);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Inactive;
TIM_OCInitStructure.TIM_Pulse = Channel2Pulse;
TIM_OC2Init(TIM1, &TIM_OCInitStructure);

/* TIM1 counter enable and output enable */
TIM_CtrlPWMOutputs(TIM1, ENABLE);

/* Select TIM1 as Master */
TIM_SelectMasterSlaveMode(TIM1, TIM_MasterSlaveMode_Enable);
TIM_SelectOutputTrigger(TIM1, TIM_TRGOSource_Update);

TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Gated);
TIM_SelectInputTrigger(TIM2, TIM_TS_ITR0);

TimerPeriod = 625;        /* Vertical lines */
Channel2Pulse = 2;        /* Sync pulse */
Channel3Pulse = 24;        /* Sync pulse + Back porch */
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
TIM_OCInitStructure.TIM_Pulse = Channel2Pulse;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Set;
TIM_OC2Init(TIM2, &TIM_OCInitStructure);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Inactive;
TIM_OCInitStructure.TIM_Pulse = Channel3Pulse;
TIM_OC3Init(TIM2, &TIM_OCInitStructure);

/*    TIM2 counter enable and output enable */
TIM_CtrlPWMOutputs(TIM2, ENABLE);

/* Interrupt TIM2 */
nvic.NVIC_IRQChannel = TIM2_IRQn;
nvic.NVIC_IRQChannelPreemptionPriority = 1;
nvic.NVIC_IRQChannelSubPriority = 0;
nvic.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&nvic);
TIM_ITConfig(TIM2, TIM_IT_CC3, ENABLE);

/* Interrupt TIM1 */
nvic.NVIC_IRQChannel = TIM1_CC_IRQn;
nvic.NVIC_IRQChannelPreemptionPriority = 1;
nvic.NVIC_IRQChannelSubPriority = 0;
nvic.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&nvic);
TIM_ITConfig(TIM1, TIM_IT_CC2, ENABLE);

TIM_Cmd(TIM2, ENABLE);
TIM_Cmd(TIM1, ENABLE);

is the signal still on pa1? this is pretty high level hal stuff, but looks right either full remap or 0b01 partial remap should put timer2 channel2 on pb3. — old_timer
– old_timer, Commented Jul 10, 2017 at 19:37
ahh search pb3 in the docs, pb3 is used for jtag/swd look at the SWJ_CFG register/bits...change them to 0b010 so you can still have SWD functionality. — old_timer
– old_timer, Commented Jul 10, 2017 at 19:39
same AFIO_MAPR register that controls the TIM2 alternate function pins — old_timer
– old_timer, Commented Jul 10, 2017 at 19:40

Batperson · Accepted Answer · 2017-07-11 19:18:00Z

1

Thanks @old_timer, that put me on the right track. SWO is enabled by default, which is on PB3 and needs to be disabled.

GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable, ENABLE);
GPIO_PinRemapConfig(GPIO_FullRemap_TIM2, ENABLE);

does the trick. The two remappings need to be done separately, combining them does not work.

answered Jul 11, 2017 at 19:18

Batperson

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