ARM LPC2129 Mini Development Board – UART0 Interfacing

In ARM LPC2129, there are two UART modules named by UART0 and UART1. Considering UART0 communication, two port pins are used – P0.0(transmission), P0.1(reception).

This Mini Development Board features 4 different connections for on board UART0 communication, they are:

USB via CP2102
Serial RS232 via MAX232
RMC connecter (GND,TXD0,RXD0,Vout) 3V3/5V level
Zigbee compatible connector on top and bottom side

UART0 communication via USB/Serial port is selected using jumpers J7 and J9. Through RMC connecter,UART0 can be used in two voltage levels of 3V3/5V which can be selected using jumper J16. While using UART0 communication PROGRAMMER switch should in manual mode else communication is not possible.

Sample code to test both transmission & reception of UART0 is given below. Initially the string “Checking UART0” to gets transmitted. Upon receiving a character, the same gets retransmitted.

Schematic:Sample code :

/*******************************************************************************************************
*                                       UART0 PROGRAM                                                  *
********************************************************************************************************
*                                     HEADER DECLARATIONS                                              *
*******************************************************************************************************/
#include<lpc21xx.h>

/*******************************************************************************************************
* Function    : Uart_Init
*
* Description : UART_0 initialization function
*               
* Parameter   : None
*******************************************************************************************************/
void Uart_Init(void)
 {
   U0LCR=0X83;                           /* line control registor                                     */
   U0DLL=0XC3;                           /* baud rate registor                                        */
   U0DLM=0X00;                           /* baud rate registor                                        */
   U0LCR=0X03;                           /* line control registor                                     */
 } 

/******************************************************************************************************
* Function    : Uart_Data
*
* Description : UART_0 data transmission function
*               
* Parameter   : data
******************************************************************************************************/
void Uart_Data(unsigned char data )
 {
   U0THR = data;
   while((U0LSR & 0X20)!= 0X20);
 }

/******************************************************************************************************
* Function    : Uart_String
*
* Description : UART_0 group of data transmission function
*               
* Parameter   : dat
******************************************************************************************************/
void Uart_String(unsigned char *dat)
 {
    while(*dat!='\0') 
    {
         Uart_Data(*dat);
         dat++;
    }
 }

/*******************************************************************************************************
*                                PORT INITIALIZATION FUNCTION                                          *
*******************************************************************************************************/
void Port_Initial(void)	
 {
    PINSEL0  =  0x00000005;
 } 

/*******************************************************************************************************
*                                         CODE AREA                                                    *
*******************************************************************************************************/	
int main()
 {
    Port_Initial();                         /* Function to initialize the ports                       */
    Uart_Init();                            /* Initialization of Uart0                                */
    Uart_String("Checking UART0");	
    while(1)
    {
     if((U0LSR&0X01)==0X01)
     {
      U0THR  = U0RBR;
      while((U0LSR&0X20)!=0X20);
     }
    }
 }

/*********************************************END******************************************************/

/*******************************************************************************************************

* UART0 PROGRAM *

********************************************************************************************************

* HEADER DECLARATIONS *

*******************************************************************************************************/

#include<lpc21xx.h>

/*******************************************************************************************************

* Function : Uart_Init

* Description : UART_0 initialization function

* Parameter : None

*******************************************************************************************************/

void Uart_Init(void)

{

U0LCR=0X83; /* line control registor */

U0DLL=0XC3; /* baud rate registor */

U0DLM=0X00; /* baud rate registor */

U0LCR=0X03; /* line control registor */

}

/******************************************************************************************************

* Function : Uart_Data

* Description : UART_0 data transmission function

* Parameter : data

******************************************************************************************************/

void Uart_Data(unsigned char data )

{

U0THR = data;

while((U0LSR & 0X20)!= 0X20);

}

/******************************************************************************************************

* Function : Uart_String

* Description : UART_0 group of data transmission function

* Parameter : dat

******************************************************************************************************/

void Uart_String(unsigned char *dat)

{

while(*dat!='\0')

{

Uart_Data(*dat);

dat++;

}

/*******************************************************************************************************

* PORT INITIALIZATION FUNCTION *

*******************************************************************************************************/

void Port_Initial(void)

{

PINSEL0 = 0x00000005;

}

/*******************************************************************************************************

* CODE AREA *

*******************************************************************************************************/

int main()

{

Port_Initial(); /* Function to initialize the ports */

Uart_Init(); /* Initialization of Uart0 */

Uart_String("Checking UART0");

while(1)

{

if((U0LSR&0X01)==0X01)

{

U0THR = U0RBR;

while((U0LSR&0X20)!=0X20);

}

/*********************************************END******************************************************/

OUTPUT:

The following screenshots explain how to test the sample code.
Realterm (Download)

Step 1:Open the Realterm

Step 2: RealTerm opens as shown below

Step 3: Go to ‘Port’ option, set correct baudrate (which is set as 9600 in the sample code) and give correct port number.

Step 4: Click ‘Change’ (encircled in red) to apply the changes. Now check the status of Port. If it is closed, click ‘Open’ button (encircled in green) to open it.

Step 5: The data transmitted from the board can be viewed as shown below.

Step 6: To check reception, go to Send option, type the string in the space provided(encircled in green) and click Send ASCII button. The first “hello” in green colour is transmitted from PC & that in yellow colour is retransmitted by the controller

Topics related to ARM LPC2129 Mini Development Board:

Resources

Softwares
- Keil uVision4 IDE
- Flash Utility Tool
Datasheets
- LPC2129
- MCP 2551
- MCP 9700
- LM 7805
- LD 1117
- MAX 232

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