Hello everyone,

I am a beginner with the MSP430 and my first application is a 
communication between two MSP430s via UART.

The first step I wanted to do is to send a byte.
I connected a oscilloscope to the UTXD0 pin but I can't see the byte, 
that should be transmitted.
So, I'm not sure if I configured the UART in the right way, or if I 
have set all bits correctly at the right position.
This is my code:

;-------------------------------

#include  "msp430x14x.h"

            ORG     01100h          ;Program Start
RESET       mov.w   #0A00h,SP       ; Initialize 'F149 stackpointer
            call    #Init_Sys       ;
       
Mainloop    nop
            jmp     Mainloop        ; Do nothing
               
Init_Sys                            ; Initalize

StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT
            
            bis.b   #030h,&P3SEL    ; P3.4,5 = USART0 TXD/RXD
            bis.b   #010h,&P3DIR    ; P3.4 = output direction
            
SetupUART0  
            clr.b   &TXBUF0         ; Clear TXBUF0      
            mov.b   #0D1h,&UCTL0    ; Parity enabled
                                    ; Even parity
                                    ; 8-bit data
                                    ; SWRST enabled
            bis.b   #010h,&UTCTL0   ; Source ACLK
            mov.b   #00Dh,&UBR00    ; 32k/2400 - 13.65
            mov.b   #000h,&UBR10    ; 32k 2400
            mov.b   #06Bh,&UMCTL0   ; 32k 2400 modulation 
            
            bic.b   #SWRST,&UCTL0   ; Clear SWRST
            bis.b   #UTXIE0,&IE1    ; Enable USART0 TX interrupt
            bis.b   #URXIE0,&IE1    ; Enable USART0 RX interrupt
            eint                    ; General enable interrupts
             
tx1         bit.b   #UTXIFG0,&IFG1  ; USART0 TX buffer ready?
            jz      tx1             ; Jump is TX buffer not ready
                                            
            ret                     ; Return from subroutine
          
USART_ISR                           ; Echo back RXed character
TX1         bit.b   #UTXIFG0,&IFG1  ; USART0 TX buffer ready?
            jz      TX1             ; Jump is TX buffer not ready
            mov.b   &RXBUF0,&TXBUF0 ; TX -> RXed character
            reti                    ; 

UART_TRANSMIT
            nop
            reti
                  
; Interrupt Vectors Used MSP430x13x/14x        

            ORG     0FFFEh                  ; 
            DW      RESET                   ; 
            ORG     0FFF2h                  ; 
            DW      UART0RX_VECTOR          ; USART0 receive
            DW      USART_ISR               ; USART0 receive
            ORG     0FFF0h                  ; 
            DW      UART_TRANSMIT           ; USART0 transmit
           end

;-------------------------------

In my view this should run endless, because when I send AAh it is 
received and send again...
But I only see a high level on the P3.4/UTXD0 pin after setting 
P3.4,5 = USART0 TXD/RXD and no signal.

I hope somebody can help me.
Nice greetings!
Bernhard

hill_valley1979 wrote:
> Hello everyone,
> 
> I am a beginner with the MSP430 and my first application is a 
> communication between two MSP430s via UART.
> 
> So, I'm not sure if I configured the UART in the right way, or if I 
> have set all bits correctly at the right position.

You haven't enabled the UART.

Refer to the data sheet for registers ME1 & ME2 (Module enable). They 
have bits for the Tx & Rx for UART0 & 1. Note the bit numbers are 
different in each register.

HTH

	Stephen

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Tel: +44 1225 868228  ||  Stephen Bashford (sbashford@sbas...)
Fax: +44 1225 868191  ||  Software Engineer
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