GPIO_PinAFConfig does not configure alternate function register

bluscape · ‎2012-04-12

Posted on April 12, 2012 at 23:01

I'm using a STM32L151C8 with ARM RealView and ST peripheral libraries.

When I try and configure an I/O pin as an alternate function it does not write the alternate function selection to the GPIOx_AFR register. After calling the GPIO_PinAFConfig function the GPIOA_AFRH register should contain a value of 0x07 (AF7) in AFRH10 and AFRH9 but they remain zero.

#define USART_TXD_PIN GPIO_Pin_9

#define USART_RXD_PIN GPIO_Pin_10

#define USART_TXD GPIOA

#define USART_RXD GPIOA

GPIO_InitStructure.GPIO_Pin = GSM_TXD_PIN;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_PinAFConfig(GSM_TXD, GSM_TXD_PIN, GPIO_AF_USART1);

GPIO_InitStructure.GPIO_Pin = GSM_RXD_PIN;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_PinAFConfig(GSM_RXD, GSM_RXD_PIN, GPIO_AF_USART1);

bluscape · ‎2012-04-12

Posted on April 12, 2012 at 23:09

Ok, realized my problem.

It should be: GPIO_PinAFConfig(GSM_TXD,

GPIO_PinSource9

, GPIO_AF_USART1);

and not: GPIO_PinAFConfig(GSM_TXD,

GPIO_Pin9

, GPIO_AF_USART1);