STM32F103C8Tx / USART1 remap issue

[Sam6600]

STM32CubeMX : Version 5.3.0

Package : STM32CubeF1 Firmware Package V1.8.0

Project Settings : Toolchain / IDE = TrueSTUDIO

MCU : STM32F103C8Tx

USART1 > Mode = Single Wire (Half-Duplex) > Pin usage PB6

Lib : LL

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In USART1 GPIO Configuration section of USART1 Initialization Function Generate the following code :

/**USART1 GPIO Configuration 
 PB6 ------> USART1_TX 
 */
 GPIO_InitStruct.Pin = LL_GPIO_PIN_6;
 GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
 GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_MEDIUM;
 GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_OPENDRAIN;
 LL_GPIO_Init(GPIOB, &GPIO_InitStruct);
 
 LL_GPIO_AF_EnableRemap_USART1();

​

When the program runs to LL_GPIO_AF_EnableRemap_USART1(), it will cause PB6 to issue a pull-down pulse, which will cause trouble to the UART receiver.

This problem can be ruled out by call LL_GPIO_AF_EnableRemap_USART1() before LL_GPIO_Init().