UART issue for reading 2 or more bytes length

[GGhed.1]

I am having an issue with the UART1 communication between two devices (Computer and a STM8S208 board).

I implemented software in the computer that writes two bytes length of data to the STM8

• the first byte that acts as an identifier;

•the second byte was the data that I wanted to write at VLS memory,

However, at the STM8, only the first byte was read and twice, For instance, I sent the identifier 0x04 and the data 0x90, but only the byte 0x04 was read and stored in the buffer as: (0x04 , 0x04 ).

Now I am implementing it reading 1-byte lenght each time via a UART interruption, but I am afraid that it could let the firmware more prone to bugs, in case of the data, have the same value of the identifier byte - Some of my data are 2 bytes long + 1 byte for Identifier.

I believe that the best solution is to send it as one byte for identifier plus two bytes for data, altogether.

But how could I implement it or why only the first byte is being read repeatly?

Below are the functions for Receiving and Writing data in the STM8:

void UART1_ReceiveBytes(uint8_t * buf, uint8_t numberOfBytes)
{
    while (numberOfBytes > 0){
        *(buf++) = UART1_ReceiveData8();
        numberOfBytes--;
    }
}
 
 
void UART1_SendBytes(uint8_t *data, unsigned int numberOfBytes)
{
    while (numberOfBytes > 0) {
        UART1_SendData8(*data++);
        numberOfBytes--;
        while(UART1_GetFlagStatus(UART1_FLAG_TXE) == RESET);
    }
}

UART Setup:

void UART1_setup(void)
{
    UART1_DeInit();
    UART1_Init( 9600, 
                UART1_WORDLENGTH_8D,
                UART1_STOPBITS_1,
                UART1_PARITY_NO,
                UART1_SYNCMODE_CLOCK_DISABLE,
                UART1_MODE_TXRX_ENABLE);
    
    UART1_ITConfig(UART1_IT_RXNE_OR, ENABLE);
    enableInterrupts();
    
    UART1_Cmd(ENABLE);
}

[Cristian Gyorgy]

C compilers are great! But, you would best know what they do, and the functions you use!

"UART1_ReceiveData8();" - is this a library function? What does it do? Just read the UART rx input register, or it waits for a byte to actually be available in the rx register and than it reads it?

[GGhed.1]

Yes, it is from the STM8 UART1 library and this function just read and returns the most recent received byte by the UART peripheral

[Cristian Gyorgy]

"this function just read and returns the most recent received byte" - right, so if you have 0x04 in the data input register, you can read the register 100 times and get 100 times the 0x04 value!

I suggest you check if there is new data available in the rx register and than read it. Or better yet: use interrupts!