STM32 UART remapping

When designing the schematic diagram, I found that there was a conflict between the pin allocations and needed to remap the pins. I learned from the manual that there are many I/O ports on STM32, and there are also many built-in peripherals such as I2C, ADC, ISP, USART, etc. In order to save lead pins, these built-in peripherals basically share pins with I/O ports, that is, the multiplexing function of I/O pins. However, STM32 has another special feature: many I/O pins of multiplexed built-in peripherals can be led out from different I/O pins through the remapping function, that is, the pins of the multiplexing function can be changed through the program.

The first time I did this, I felt unsure, so I implemented it on the STM32F103RBT6 board for USART1. The following is the relevant test code:

 

/****************************************************** ******************************

//Function name: void Uart1_Init(void)

//Function: Serial port (USART1) remapping initialization configuration function, TX PA9~PB6 RX PA10~~PB7

*************************************************** ***************************/

void Uart1_Init(void)

{

 RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO,ENABLE); //Enable port B and multiplex function clock

 GPIO_PinRemapConfig(GPIO_Remap_USART1,ENABLE); //Enable port remapping

 GPIO_InitTypeDef GPIO_InitStructure;

 //Uart GPIO remapping pin initialization PB6 usart1_TX PB7 USART_RX

 GPIO_InitStructure.GPIO_Pin=GPIO_Pin_6;

 GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF_PP; //Push-pull output

 GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;

 GPIO_Init(GPIOB,&GPIO_InitStructure);

 

 GPIO_InitStructure.GPIO_Pin=GPIO_Pin_7;

 GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IN_FLOATING; //Floating input

 GPIO_Init(GPIOB,&GPIO_InitStructure);

 

 

 RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);

 USART_InitTypeDef USART_InitStructure;

//Serial port parameter configuration: 9600,8,1, no parity check, no hard flow control, enable sending and receiving

 USART_InitStructure.USART_BaudRate = 9600;

 USART_InitStructure.USART_WordLength = USART_WordLength_8b;

 USART_InitStructure.USART_StopBits = USART_StopBits_1;

 USART_InitStructure.USART_Parity = USART_Parity_No;

 USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

 USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

 USART_Init(USART1, &USART_InitStructure);

 USART_ITConfig(USART1, USART_IT_RXNE,ENABLE); //Serial port receive interrupt

 USART_Cmd(USART1, ENABLE);

}

A brief analysis of the remapping steps is:

 

1. Turn on the remapped clock and the USART remapped I/O port pin clock,

 RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB |RC C_APB2Periph_AFIO,ENABLE);

2.I/O port remapping is enabled.

  GPIO_PinRemapConfig(GPIO_Remap_USART1,ENABLE);

3. Configure the remapped pins. Here you only need to configure the remapped I/Os, and the original ones do not need to be configured.

 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;

 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

 GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;

 GPIO_Init(GPIOB, &GPIO_InitStructure);

 

 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;

 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;

 GPIO_Init(GPIOB, &GPIO_InitStructure);

Just follow these three steps to get it done easily.