STM32F4Â GPIO_ReadInputData while in AF mode?

[Bogdan]

Posted on January 09, 2017 at 21:35

Hello,

i have a bldc motor with hall sensors, each hall sensor is conected to PA0 PA1 PA2  which coresponds to CH1,2,3 of timer2.

So in my gpio init routine i have declared the gpio's as following

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 |GPIO_Pin_2;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource0, GPIO_AF_TIM2);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM2);GPIO_PinAFConfig(GPIOA, GPIO_PinSource2, GPIO_AF_TIM2);

And somewhere in the timer2 cc1 irq handler i want to read the bit order of the 3 hall sensors.

i was thinking ading something like this   uint16_t pdata = GPIO_ReadInputData(GPIOA) & 0x0007 

But i read some unusual values.

Do i need another mode for GPIO in order to read the corect data? i was thinking of using GPIO_Mode_IN , but in this case will i am able to trigger the timer2 ?

[Tesla DeLorean]

Posted on January 09, 2017 at 21:41

You should be able to read the GPIOx->IDR in all modes except Analogue In, which turns of the Schmitt Trigger on the input.

[Bogdan]

Posted on January 09, 2017 at 23:40

Hello Clive, 

Thanks for the information. After seeing this, i was concerned about framing errors on USART.... i keep forgeting to check the stm32f4xx.h file.... i was having HSE_VALUE 25 MHZ , and my discovery board has 8MHZ  ... anyway... redefined the PLL settings and HSE valyue, and the USART behaves normal, i can see the corect data from the hall GPIO inputs (hall3 is MSB)