arm serial communication

Asynchronous communication

The so-called asynchronous communication means that data is transmitted in characters. The transmission between characters is completely asynchronous, while the transmission between bits is basically synchronous.

The characteristics of asynchronous serial communication can be summarized as follows

   1) Transmit information in characters

   2) The interval between two adjacent characters is of any length

   3) Because the bits in a character are limited in length, the required receiving clock and sending clock only need to be close.

   4) The characteristics of the asynchronous mode are: asynchronous between characters, and synchronous within each character

Asynchronous serial data format

   1) 1 start bit, defined as low level 0

   2) 5 to 8 data bits, i.e. valid information to be transmitted

   3) 1 parity bit

   4) 1~2 stop bits, specified as high level 1

Synchronous Serial

The so-called synchronous communication means that data transmission is based on data blocks (a group of characters), and the characters and the bits within the characters are synchronized.

The characteristics of synchronous serial communication can be summarized as follows:

   1) Transmit information in blocks

   2) In a data block (information frame), there is no space between characters.

   3) Because a transmitted data block contains a lot of data, the receiving clock and the sending clock are strictly synchronized, usually with a synchronous clock

Data format of synchronous serial mode

   1) Two synchronization characters are used as the start mark of a data block (information frame).

   2) n consecutively transmitted data

   3) Two-byte cyclic redundancy check code (CRC)

example

#include "2410lib.h"

void uart0_test(void);

int main(int argc, char **argv)

{

   sys_init();

   uart_printf("n Embest Arm S3CEB2410 Evaluation Boardn");

while(1)

   {

       uart0_test();

   }        

}

void uart0_test()

{

char cInput[256];

   UINT8T ucInNo=0;

char c;

   uart_init(0,115200,0);

   uart_printf("n UART0 Communication Test Examplen");    

   uart_printf("Please input words, then press Enter:n");

while(1)

   {

       c=uart_getch();

       uart_printf("%c",c);

if(c!='r') //enter key

           cInput[ucInNo++]=c;

else

       {

           cInput[ucInNo]='';

break;

       }

   }

   delay(1000);    

   uart_printf("n The words that you input are: n %sn",cInput);      

   uart_printf(" end.n");  

}