Why elements in an array elements shift?

[ahmetgunduz]

Hi, i am using stm32f4. in my project i have one transmitter and one receiver.

i transmit an 2 byte integer value using

HAL_UART_Transmit(&huart1,&temp_byte1,sizeof(temp_byte1), 500);
HAL_UART_Transmit(&huart1,&temp_byte2,sizeof(temp_byte2), 500);

and on the receiver part. i read these values using

void USART6_IRQHandler(void)
{
HAL_UART_Receive_IT(&huart6,&rx_data,1);
temp_data[rx_index]=rx_data;
			rx_index++;
			if(rx_index==2)
			{
			rx_index=0;			
			temp = ((temp_data[0]<<8)|temp_data[1]);
			if(temp!=79){ //sometimes i see a 79 in my buffer!
			hc05_flag = 3; //irrelevant flag with this question
			nm=0; //irrelevant flag with this question				
			}
}

it works fine for one time. but after, i see  temp_data[1]  in  temp_data[0]. it shift 8 bits and i see a big  temp value (63744 etc.) . where is my problem?

[raptorhal2]

My guess is that this is a classroom exercise.

Your problem is that you have two processes and no method to synchronize related transmits and receives.

Its your project. I will leave it up to you to figure out how to keep them in sync.

Cheers, Hal

[Tesla DeLorean]

HAL_UART_Receive_IT() does not work like this. You need to collect the data in the callback, as the function you're using should return immediately, not when it actually has data.

[Piranha]

You must use HAL_UART_IRQHandler() and HAL_UART_RxCpltCallback().