How to clear UART's RX_buffer in stm32f030cct6

[NHing.1]

Hello Forum,

I am using stm32f030cct6 and Quectel L86 GPS module for my application.

I am doing coding on STMCubeIDE, using HAL libraries.

The GPS module is in continuously receiving data mode.

I am receiving that data on uart in a buffer.

Max size of buffer i kept is 1500, which is sufficient.

My main question is that while receiving the data i need to clear the previously stored data from buffer.

For a while it receives variation in data but after some time it keep same data till reset of MCU.

I want to clear the previous data as it receives fresh data each second.

Can anyone tell me how to do that?

This is the data that received on UART

$PMTK011,MTKGPS*08
$PMTK010,001*2E
$PMTK011,MTKGPS*08
$PMTK010,002*2D
$GPRMC,064512.498,V,,,,,0.00,0.00,270121,,,N*4B
$GPVTG,0.00,T,,M,0.00,N,0.00,K,N*32
$GPGGA,064512.498,,,,,0,0,,,M,,M,,*49
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GPGSV,1,1,00*79
$GLGSV,1,1,00*65
$GPGLL,,,,,064512.498,V,N*7B
$GPTXT,01,01,02,ANTSTATUS=OPEN*2B
 
$GPRMC,064513.498,V,,,,,0.00,0.00,270121,,,N*4A
$GPVTG,0.00,T,,M,0.00,N,0.00,K,N*32
$GPGGA,064513.498,,,,,0,0,,,M,,M,,*48
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GPGSV,1,1,00*79
$GLGSV,1,1,00*65
$GPGLL,,,,,064513.498,V,N*7A
$GPTXT,01,01,02,ANTSTATUS=OPEN*2B

@Guenael Cadier

[KnarfB]

Sounds like an issue with your code (not shown). Use memset to clear the buffer before the next message comes in?

Receive with HAL_UARTEx_ReceiveToIdle_IT(&huart2, &buffer, sizeof(buffer) ); and in the callback, you get the number of bytes read:

void HAL_UARTEx_RxEventCallback(UART_HandleTypeDef *huart, uint16_t Size)
{
	// process message of size Size in buffer
	HAL_UARTEx_ReceiveToIdle_IT(&huart2, &buffer, sizeof(buffer) );
}

[NHing.1]

Hello @KnarfB​,

Thanks for the reply.

I am using

HAL_UART_Receive(&GPSUART,(uint8_t *)ch,MAX,500); /* Receiving data from GPS on UART_1*/
str_len = strlen(ch);
HAL_UART_Transmit(&TerminalUART,(uint8_t *)ch,str_len,500);  /*Transmitting data to Terminal UART_2*/

 this in while loop

when i use memset after transmit loop get stops

[KnarfB]

Put memset immediately before HAL_UART_Receive.

Note that HAL_UART_Receive returns after either MAX bytes were read or the timeout (500ms) elapsed.

[Piranha]

An array of some data is not a zero terminated string. You cannot use strlen() or other string manipulation functions on it.

[NHing.1]

Hello @KnarfB​ , @Piranha​ 

I use memset before receiving data

memset(ch,0,MAX);
 
HAL_UART_Receive(&GPSUART,(uint8_t *)ch,MAX,1000); /* Receiving data from GPS on UART_1*/
str_len = strlen(ch);
HAL_UART_Transmit(&TerminalUART,(uint8_t *)ch,str_len,1000);/*Transmitting data to Terminal UART_2*/

and i got this output

$PMTK011,MTKGPS*08
$PMTK010,001*2E
$PMTK011,MTKGPS*08
$PMTK010,002*2D
$GPRMC,063153.974,V,,,,,0.00,0.00,040221,,,N*40
$GPVTG,0.00,T,,M,0.00,N,0.00,K,N*32
$GPGGA,063153.974,,,,,0,0,,,M,,M,,*40
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GPGSV,1,1,00*79
$GLGSV,1,1,00*65
$GPGLL,,,,,063153.974,V,N*72
$GPTXT,01,01,02,ANTSTATUS=OPEN*2B
 
 
330
 
$GPRMC,063154.974,V,,,,,0.00,0.00,040221,,,N*47
$GPVTG,0.00,T,,M,0.00,N,0.00,K,N*32
$GPGGA,063154.974,,,,,0,0,,,M,,M,,*47
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GPGSV,1,1,00*79
$GLGSV,1,1,00*65
$GPGLL,,,,,063154.974,V,N*75
$GPTXT,01,01,02,ANTSTATUS=OPEN*2B
 
 
256
 
$
 
1

 and HAL_UART_Receive returns after timeout

[NHing.1]

Hello @Piranha​ ,

I didn't understand your point regarding the manipulation.

[NHing.1]

Hello @KnarfB​ ,

I need some updates on this.

[Alexander Stankov]

https://www.youtube.com/watch?v=EsZLgqhqfO0&t=455s - watch right after the 13-minute mark. Maybe this can give you an idea. There is a (Rx/Tx)HalfCpltCallback or something in the HAL_Drivers. And UART can also use DMA.