MSP430 serial receive-RX problem

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I am trying to get the TX/RX echo example program to work on an Olimex
Easyweb II MSP430 starter kit. I am able to receive character on the
host PC using HyperTerminal to monitor the serial connection (TX on
embedded microcontroller). However, it does not receive any characters
sent from the terminal program, and I am just about out of options on
how to debug this problem. Anyone that could provide any help? I post
my code (small changes from TI example to adapt to other oscillator

Thanks, regards


#include <msp430x14x.h>

void main(void)
  unsigned int i;
  WDTCTL = WDTPW + WDTHOLD;             // Stop WDT
  P3SEL |= 0x30;                        // P3.4,5 = USART0 TXD/RXD
  P3DIR &= ~0x20;  // set bit 5 to low = input
  P3DIR |= 0x10;  // set bit 4 to high = output
  BCSCTL1 |= XTS;                       // ACLK = LFXT1 = HF XTAL

  IFG1 &= ~OFIFG;                       // Clear OSCFault flag
  for (i = 0xFF; i > 0; i--);           // Time for flag to set
  while ((IFG1 & OFIFG));               // OSCFault flag still set?

  BCSCTL2 |= SELM_3;                    // MCLK = LFXT1 (safe)
  ME1 |= UTXE0 + URXE0;                 // Enable USART0 TXD/RXD
  UCTL0 |= CHAR;                        // 8-bit character
  UTCTL0 |= SSEL0;                      // UCLK = ACLK
  UBR00 = 0x41;                         // 8Mhz/9600 = 0x341
  UBR10 = 0x03;                         //
  UMCTL0 = 0x00;                        // no modulation
  UCTL0 &= ~SWRST;                      // Initialize USART state
  IE1 |= URXIE0;                        // Enable USART0 RX interrupt

  TXBUF0 = 'x';

  _BIS_SR(LPM0_bits + GIE);             // Enter LPM0 w/ interrupt

#pragma vector=UART0RX_VECTOR
__interrupt void usart0_rx (void)
  while (!(IFG1 & UTXIFG0));            // USART0 TX buffer ready?
  TXBUF0 = RXBUF0;                      // RXBUF0 to TXBUF0

Re: MSP430 serial receive-RX problem

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Without digging up my examples (I use MSP430 a lot, but I wrote the UART
code a long time ago), why not try it in stages:

(0) Is HyperTerminal broken? I had this recently when playing with an
ez80. I used TeraTerm instead, and all was fine.

(1) get rid of the interrupt. Loop transmitting a character in main().
Does the output appear?

(2) Once (1) works, wait to receive a character in main and echo it. Use
the scope to check that the character actually reaches the pin.

(3) Then put the lot back in interrupt. Make it flash an LED or an
output you can scope when it goes through the ISR.

Paul Burke

Re: MSP430 serial receive-RX problem
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I'd second that as a first step (!). HyperTerminal is not very happy unless
all the control lines are connected and even then it gets things wrong.
TeraTerm is much easier to use, has macros and doesn't pester you with
dialog boxes.


Re: MSP430 serial receive-RX problem

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No, not if you configure it for Flow Control = none.

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Agreed. Minicom even nicer.

- Mark ->

Re: MSP430 serial receive-RX problem
Thanks all for your replies. As is, my first sample code printed a
character 'x' in Hyperterminal, thus everything seemed fine in baud
rate settings, register settings and so on. Every other example I've
tried has worked like charm every time. But, reading your suggestions
led me to try with Hyperterminal once more, with flow control = none.
And what do you know, it worked!!

I'll try Tera Term next time! But a brief search for Tera Term led me
to think it wasn't supported by Win XP, but I've just hit another site
which seems to support TT Pro for Win XP.

Well, thanks for now.



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Re: MSP430 serial receive-RX problem

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Tera Term is one of these rare programs which does everything the author
wanted it to do, and is (as far as I know) bug-free.  Thus it has not
changed in 5 years, simply because it does not need to be changed.  As far
as I have heard, it works fine in all 32-bit windows (and there is a win3.1
version too).  Since it is open source, a few others have made extensions
for ssh and webby stuff, but the serial port stuff is the same.

TeraTerm (was: MSP430 serial receive-RX problem)
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... snip ...
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I found I had a distribution from 1998 tucked away on my drive,
and it looks good.  Do you know offhand where the source is to be
found?  My only wishes so far are that it had a single page
printable helpfile/manual and that the 'monitor communications'
ability had been implemented.

 "This is a wonderful answer. It's off-topic, it's incorrect,
  and it doesn't answer the question."  --  Richard Heathfield

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Re: TeraTerm (was: MSP430 serial receive-RX problem)

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Google is your friend - the tera term pro home page is the first hit when
googling for "tera term pro":

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