How to send uint32_t hex via USART

[yongjie989]

Posted on March 26, 2016 at 05:33

Hi All,

I would like to send uint32_t hex via USART, but no idea how to do it.

for example:

uint32_t buffer[2];

buffer[0] = 0x12345678;

buffer[1] = 0x87654321;

USART_puts(buffer[0])  <-- ????  the USART_puts length is uint8_t not 32-bit

void USART_puts(uint8_t * data){

    uint8_t u_i=0;

    while(data[u_i]!='\0')

    {

        USART_SendData(USART6, data[u_i++]);

        while(USART_GetFlagStatus(USART6, USART_FLAG_TXE) == RESET);          

    }

}

Thank you.

[macgeorgio]

Posted on March 26, 2016 at 06:48

Hello,

in order to keep the USART_puts function as is (send 8bit characters), I propose you to create an intermediate function which will split the buffer of 32bit elements to a buffer of 8bit elements.

A simple function to do this would be:

void splitbuffer(uint32_t* buf32bit,uint8_t* buf8bit)

{

    int i;

    for (i=0;i<sizeof(buf32bit)/4;i++)

    {

        buf8bit[4*i+0]=(buf32bit[i]>>24)&0xFF;

        buf8bit[4*i+1]=(buf32bit[i]>>16)&0xFF;

        buf8bit[4*i+2]=(buf32bit[i]>>8)&0xFF;

        buf8bit[4*i+3]=(buf32bit[i])&0xFF;

    }

}

and you would call it by:

splitbuffer(buffer32bit,buffer8bit);

(remember to declare a buffer8bit[] array with four times the number of elements of buffer32bit.

How the function works is quite simple:

- The for loop runs for every element of the 32bit buffer after determining its size (sizeof returns the size of the 32bit buffer in bytes and each element is 4 bytes long).

- For every element a shifting is performed starting from the Most Significant Byte (>>24) with a bitwise AND to isolate the specific byte.

- The final 8bit buffer is little endian, meaning that the most significant byte is at the first position and the least significant byte is at the last position.

[Tesla DeLorean]

Posted on March 26, 2016 at 11:16

void USART_buffer(uint8_t * data, size_t size)
{
while(size--)
{
while(USART_GetFlagStatus(USART6, USART_FLAG_TXE) == RESET);// Check it is empty FIRST 
USART_SendData(USART6, *data++);
}
}
USART_buffer((void *)buffer, sizeof(buffer));
USART_puts(buffer[0]); // INCORRECT, buffer[0] is NOT a pointer