Small problem of STM8s using library to configure port

　　When used, the PA2 port needs to be set to push-pull output to control an external power switch. The port initialization procedure is as follows:

　　　　GPIO_DeInit(GPIOA);

　　　　GPIO_Init(GPIOA,GPIO_PIN_2,GPIO_MODE_OUT_PP_HIGH_SLOW);

　　After the setting is completed, the port will immediately output a high level, so another sentence is added:

　　　　GPIO_WriteLow(GPIOA,GPIO_PIN_2);

　　After completion, it was found that the powered device would be triggered when it was powered on for the first time, and the program did not output a high level on PA2. This powered device is equipped with a power supply battery and will start if a high level is detected on the port.

Using an oscilloscope to observe the PA2 port, I found that there was a short pulse at the moment of power-on, which seemed to be the problem. I checked the source code of the library function:

void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_Pin_TypeDef GPIO_Pin, GPIO_Mode_TypeDef GPIO_Mode)
{

　　assert_param(IS_GPIO_MODE_OK(GPIO_Mode));
　　assert_param(IS_GPIO_PIN_OK(GPIO_Pin));

　　/* Reset corresponding bit to GPIO_Pin in CR2 register */
　　GPIOx->CR2 &= (uint8_t)(~(GPIO_Pin));

　　/*-----------------------------*/
　　/* Input/Output mode selection */
　　*-----------------------------*/

　　if ((((uint8_t)(GPIO_Mode)) & (uint8_t)0x80) != (uint8_t)0x00) /* Output mode */
　　{
　　　　if ((((uint8_t)(GPIO_Mode)) & (uint8_t)0x10) != (uint8_t)0x00) /* High level */
　　{
　　　　GPIOx->ODR |= (uint8_t)GPIO_Pin;
　　}
　　else /* Low level */
　　{
　　　　GPIOx->ODR &= (uint8_t)(~(GPIO_Pin));
　　}
　　/* Set Output mode */
　　　　GPIOx->DDR |= (uint8_t)GPIO_Pin;
　　}
　　else /* Input mode */
　　{
　　　　/* Set Input mode */
　　　　GPIOx->DDR &= (uint8_t)(~(GPIO_Pin));
　　}

/*------------------------------------------------------------------------*/
/* Pull-Up/Float (Input) or Push-Pull/Open-Drain (Output) modes selection */
/*------------------------------------------------------------------------*/

　　if ((((uint8_t)(GPIO_Mode)) & (uint8_t)0x40) != (uint8_t)0x00) /* Pull-Up or Push-Pull */
　　{
　　　　GPIOx->CR1 |= (uint8_t)GPIO_Pin;
　　}
　　else /* Float or Open-Drain */
　　{
　　　　GPIOx->CR1 &= (uint8_t)(~(GPIO_Pin));
　　}

　　/*-----------------------------------------------------*/
　　/* Interrupt (Input) or Slope (Output) modes selection */
　　/*-----------------------------------------------------*/

　　if ((((uint8_t)(GPIO_Mode)) & (uint8_t)0x20) != (uint8_t)0x00) /* Interrupt or Slow slope */
　　{
　　　　GPIOx->CR2 |= (uint8_t)GPIO_Pin;
　　}
　　else /* No external interrupt or No slope control */
　　{
　　　　GPIOx->CR2 &= (uint8_t)(~(GPIO_Pin));
　　}
}

　　From the source code, CR2 is cleared first. Then write the DDR direction register 1 for output, 0 for input, and then CR1. This can be used with DDR to determine 4 modes: when DDR is 0, CR1 is 0 for floating input, when CR1 is 1 for pull-up input, when DDR is 1, CR1 is 0 for open-drain output, and when CR1 is 1 for push-pull output. When DDR is 0, CR1 is the switch for external interrupts, 1 is on, 0 is off, and when DDR is 1, it controls the slew rate. If a steeper edge is required, it can be set to 1.

　　I don't know why this happens. Hardware simulation found that CR1 will be pulled high after it is set. Later, I used the register method to set it normally. The code is as follows:

　　GPIOA->CR2 |= 0x04;
　　GPIOA->DDR |= 0x04;
　　GPIOA->CR1 |= 0x04;