USART Not Receiving Data (Polling)

[tonyblake9]

Posted on May 31, 2017 at 17:06

Hi guys,

So I'm using an STM32F1 and am trying to send data from a serial terminal (RealTerm) to USART3 via a FTDI USB-UART converter cable. I have written code to poll for data on the RX line but for some reason my USART_FLAG_RXNE is not being set when I send data from the terminal. Here is my code (no errors):

void USART3_Config(void)

{ GPIO_InitTypeDef GPIO_InitStruct; USART_InitTypeDef USART_InitStruct; // Clock Config RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3,ENABLE); RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB,ENABLE); RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

// GPIO Config

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_10; // USART3 TX GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP; GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOB, &GPIO_InitStruct); GPIO_InitStruct.GPIO_Pin = GPIO_Pin_11; // USART3 RX GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN_FLOATING; GPIO_Init(GPIOB, &GPIO_InitStruct); // USART Struct Config USART_InitStruct.USART_BaudRate = 9600; USART_InitStruct.USART_StopBits = USART_StopBits_1; USART_InitStruct.USART_WordLength = USART_WordLength_8b; USART_InitStruct.USART_Parity = USART_Parity_No; USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None; USART_InitStruct.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; USART_Init(USART3, &USART_InitStruct); USART_Cmd(USART3, ENABLE); }

int main(void)

{ RCC_Configuration(); ... USART3_Config(); ... while(1) { ... State = POLLING_TEST; switch (State) { ... case POLLING_TEST: while(USART_GetFlagStatus(USART3, USART_FLAG_RXNE) == RESET); sprintf(data, 'dummy'); // breakpoint here break;

Can anyone help me with this? Have I done something wrong?

Cheers,

Tony

#stm32f1 #usart #rx #polling

[tonyblake9]

Posted on May 31, 2017 at 17:09

p.s. my wiring is fine (I can transmit data fine)

[Elkin Granados]

Posted on May 31, 2017 at 18:59

Hi, checking the code I see it right. I'm not sure about this:

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_11; // USART3 RX

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN_FLOATING;

I generated an example code with CubeMX and get this:

GPIO_InitStruct.Pin = GPIO_PIN_10;

GPIO_InitStruct.Mode = GPIO_MODE_AF_PP; GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH; HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

GPIO_InitStruct.Pin = GPIO_PIN_11;

GPIO_InitStruct.Mode = GPIO_MODE_INPUT; GPIO_InitStruct.Pull = GPIO_NOPULL; HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

Maybe it could be useful for you:

https://community.st.com/0D50X00009XkXrmSAF

[Tesla DeLorean]

Posted on May 31, 2017 at 20:46

Still doesn't seem to be receiving.

https://community.st.com/0D50X00009XkdezSAB

 

Make sure to fully initialize the GPIO structure, consider using GPIO_InitTypeDef GPIO_InitStruct = { 0 };

Check the GPIO configuration view debugger peripheral review.

Check the USART SR for other errors flagging.

Consider doing a simple loop back test, ie TX connects to RX, with no other external connectivity.

[Tesla DeLorean]

Posted on June 01, 2017 at 01:08

The F1 didn't have a pin level AF multiplexor, peripheral inputs were not 'AF', because inputs can be shared by everyone without interference, so the peripheral just taps into the buffer. ie GPIOx->IDR.x

Dozens of F1 USART SPL examples have been posted, I'm loathed to have to keep fixing broken wheels.

[Tesla DeLorean]

Posted on June 01, 2017 at 04:55

This is a STM32F1 USART3 PC10/PC11 example

https://community.st.com/0D70X000006SjYUSA0

 

Not sure which F1 specifically is being discussed here. I suppose there is a possible conflict with I2C2, which could be remapped off PB10/PB11. Other than that it is more probably failing for mundane reasons. For ST boards check solder-bridge options and whether pins in question reach headers or not, or connect to other peripheral hardware.

Replicate the issue on known working hardware/designs.