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Having problems with UART P3.4 (UTXD0) on MSP430F149

Started by owaiscareer ●March 13, 2006
Hi

I am evaluating the MSP430 for a new design.  To get started, I'm
trying to put up a simple link between the micro and the computer
using the code below.  THis is a 1200 baud link using the supplied 32K
crystal.  Needless to say I do not see any of the 0xaa characters on
the PC terminal.  (i have an rs232 transceiver max2232 between the
micro and the computer uart). This transceiver works, so that is not
the problem! When I put a osc' probe on P3.4, I see an extremly
low-level signal around 200mv, I was expecing a nice 0-3V output. 
This must mean that I'm not setting up the pins correctly.  Please
advice as to what I am doing wrong.
Thanks,
Owais

CODE:


#include <msp430x14x.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD; //turn watchdog off
  
  UCTL0 = CHAR;   //char = 8 bits
  UTCTL0 = SSEL0; //uclk = aclk (from 32.768 crystal); use auxiliary
clock source

  //N = brclk/baudrate = 32.768K/1200 = 27.31
//  UBR00 = 0x1B; //lsb(N) of baud rate register
  UBR00 = 0x03; //lsb(N) of baud rate register
  UBR10 = 0x00; //msb(N) of baud rate register
  UMCTL0 = 0x4A;//set modulation cntl register

  ME1 |= UTXE0 + URXE0;  //enable transmit and receive modules for USART0
  P3SEL |= 0x30;  //P3.4 P3.5, use alternate (UART) function
  P3DIR |= 0x10;  //P3.4 = output direction 00010000
  P3DIR &= ~0x20; // set bit 5 to low = input
  P3DIR |= 0x01;  //P3.1 toggle bit (output direction)
  for(;;)
  {
    TXBUF0 = 0xAA;  //send again...
    while(!(UTCTL0 & TXEPT));
    P3OUT ^= 0x01;
//    P1OUT ^= 0x01;                      // Toggle P1.0 using
exclusive-OR
  }
}

Beginning Microcontrollers with the MSP430

Reply by Adriano Caye ●March 14, 20062006-03-14
Take a moment to read page 13-4 of the user's guide (SLAU049). There is 
a correct sequence to initialize UART described over there.

Regards,
Adriano.

owaiscareer wrote:
> Hi
> 
> I am evaluating the MSP430 for a new design.  To get started, I'm
> trying to put up a simple link between the micro and the computer
> using the code below.  THis is a 1200 baud link using the supplied 32K
> crystal.  Needless to say I do not see any of the 0xaa characters on
> the PC terminal.  (i have an rs232 transceiver max2232 between the
> micro and the computer uart). This transceiver works, so that is not
> the problem! When I put a osc' probe on P3.4, I see an extremly
> low-level signal around 200mv, I was expecing a nice 0-3V output. 
> This must mean that I'm not setting up the pins correctly.  Please
> advice as to what I am doing wrong.
> Thanks,
> Owais
> 
> CODE:
> 
> 
> #include <msp430x14x.h>
> 
> void main(void)
> {
>   WDTCTL = WDTPW + WDTHOLD; //turn watchdog off
>   
>   UCTL0 = CHAR;   //char = 8 bits
>   UTCTL0 = SSEL0; //uclk = aclk (from 32.768 crystal); use auxiliary
> clock source
> 
>   //N = brclk/baudrate = 32.768K/1200 = 27.31
> //  UBR00 = 0x1B; //lsb(N) of baud rate register
>   UBR00 = 0x03; //lsb(N) of baud rate register
>   UBR10 = 0x00; //msb(N) of baud rate register
>   UMCTL0 = 0x4A;//set modulation cntl register
> 
>   ME1 |= UTXE0 + URXE0;  //enable transmit and receive modules for USART0
>   P3SEL |= 0x30;  //P3.4 P3.5, use alternate (UART) function
>   P3DIR |= 0x10;  //P3.4 = output direction 00010000
>   P3DIR &= ~0x20; // set bit 5 to low = input
>   P3DIR |= 0x01;  //P3.1 toggle bit (output direction)
>   for(;;)
>   {
>     TXBUF0 = 0xAA;  //send again...
>     while(!(UTCTL0 & TXEPT));
>     P3OUT ^= 0x01;
> //    P1OUT ^= 0x01;                      // Toggle P1.0 using
> exclusive-OR
>   }
> }
> 
> 
> 
> 
> 
> 
> 
> .
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>
Reply by owaiscareer ●March 14, 20062006-03-14
Hi Adriano,

I looked and implemented with no progress on UART0: please see below
(I now disable the UART state machine before initializing the
registers: UCTL0 |= SWRST)

...curiously, moving the same code to UART1 makes it spit out data but
it is the wrong baud rate (250Khz) when I measure with the
oscilloscope, the data line is correctly toggling between 0 and 3.3V
though.  What gives?

Thanks,
Owais

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD; //turn watchdog off

  UCTL0 |= SWRST;
    
  UCTL0 |= CHAR;   //char = 8 bits
  UTCTL0 |= SSEL0; //uclk = aclk (from 32.768 crystal); use auxiliary
clock source

  //N = brclk/baudrate = 32.768K/1200 = 27.31
//  UBR00 = 0x1B; //lsb(N) of baud rate register
  UBR00 = 0x03; //lsb(N) of baud rate register
  UBR10 = 0x00; //msb(N) of baud rate register
  UMCTL0 = 0x4A;//set modulation cntl register

  
  ME1 |= UTXE0 + URXE0;  //enable transmit and receive modules for USART0
  
  UCTL0 &= ~SWRST;                          // Initialize USART state
machine

  P3SEL |= 0x30;  //P3.4 P3.5, use alternate (UART) function 11000000
  P3DIR |= 0x10;  //P3.4 = output direction 01000000
  P3DIR &= ~0x20; // set bit 5 to low = input 1000000
  P3DIR |= 0x01;  //P3.1 toggle bit (output direction)
  for(;;)
  {
    TXBUF0 = 0xAA;  //send again...
    while(!(UTCTL0 & TXEPT));
    P3OUT ^= 0x01;
//    P1OUT ^= 0x01;                      // Toggle P1.0 using
exclusive-OR
  }
}


--- In msp430@msp4..., Adriano Caye <adriano@...> wrote:
>
> 
> Take a moment to read page 13-4 of the user's guide (SLAU049). There
is 
> a correct sequence to initialize UART described over there.
> 
> Regards,
> Adriano.
> 
> owaiscareer wrote:
> > Hi
> > 
> > I am evaluating the MSP430 for a new design.  To get started, I'm
> > trying to put up a simple link between the micro and the computer
> > using the code below.  THis is a 1200 baud link using the supplied 32K
> > crystal.  Needless to say I do not see any of the 0xaa characters on
> > the PC terminal.  (i have an rs232 transceiver max2232 between the
> > micro and the computer uart). This transceiver works, so that is not
> > the problem! When I put a osc' probe on P3.4, I see an extremly
> > low-level signal around 200mv, I was expecing a nice 0-3V output. 
> > This must mean that I'm not setting up the pins correctly. 
Please
> > advice as to what I am doing wrong.
> > Thanks,
> > Owais
> > 
> > CODE:
> > 
> > 
> > #include <msp430x14x.h>
> > 
> > void main(void)
> > {
> >   WDTCTL = WDTPW + WDTHOLD; //turn watchdog off
> >   
> >   UCTL0 = CHAR;   //char = 8 bits
> >   UTCTL0 = SSEL0; //uclk = aclk (from 32.768 crystal); use auxiliary
> > clock source
> > 
> >   //N = brclk/baudrate = 32.768K/1200 = 27.31
> > //  UBR00 = 0x1B; //lsb(N) of baud rate register
> >   UBR00 = 0x03; //lsb(N) of baud rate register
> >   UBR10 = 0x00; //msb(N) of baud rate register
> >   UMCTL0 = 0x4A;//set modulation cntl register
> > 
> >   ME1 |= UTXE0 + URXE0;  //enable transmit and receive modules for
USART0
> >   P3SEL |= 0x30;  //P3.4 P3.5, use alternate
(UART) function
> >   P3DIR |= 0x10;  //P3.4 = output direction 00010000
> >   P3DIR &= ~0x20; // set bit 5 to low = input
> >   P3DIR |= 0x01;  //P3.1 toggle bit (output direction)
> >   for(;;)
> >   {
> >     TXBUF0 = 0xAA;  //send again...
> >     while(!(UTCTL0 & TXEPT));
> >     P3OUT ^= 0x01;
> > //    P1OUT ^= 0x01;                      // Toggle P1.0 using
> > exclusive-OR
> >   }
> > }
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > .
> > 
> >  
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> >
>
Reply by Greg Maki ●March 14, 20062006-03-14
owaiscareer wrote:
> Hi Adriano,
> 
> I looked and implemented with no progress on UART0: please see below
> (I now disable the UART state machine before initializing the
> registers: UCTL0 |= SWRST)
> 
> ...curiously, moving the same code to UART1 makes it spit out data but
> it is the wrong baud rate (250Khz) when I measure with the
> oscilloscope, the data line is correctly toggling between 0 and 3.3V
> though.  What gives?
> 
> Thanks,
> Owais
> 
> void main(void)
> {
>   WDTCTL = WDTPW + WDTHOLD; //turn watchdog off
> 
>   UCTL0 |= SWRST;
>    
>   UCTL0 |= CHAR;   //char = 8 bits
>   UTCTL0 |= SSEL0; //uclk = aclk (from 32.768 crystal); use auxiliary
> clock source
> 
>   //N = brclk/baudrate = 32.768K/1200 = 27.31
> //  UBR00 = 0x1B; //lsb(N) of baud rate register
>   UBR00 = 0x03; //lsb(N) of baud rate register
>   UBR10 = 0x00; //msb(N) of baud rate register
>   UMCTL0 = 0x4A;//set modulation cntl register
> 
>  
>   ME1 |= UTXE0 + URXE0;  //enable transmit and receive modules for USART0
>  
>   UCTL0 &= ~SWRST;                          // Initialize USART state
> machine
> 
>   P3SEL |= 0x30;  //P3.4 P3.5, use alternate (UART) function 11000000
>   P3DIR |= 0x10;  //P3.4 = output direction 01000000
>   P3DIR &= ~0x20; // set bit 5 to low = input 1000000
>   P3DIR |= 0x01;  //P3.1 toggle bit (output direction)
>   for(;;)
>   {
>     TXBUF0 = 0xAA;  //send again...
>     while(!(UTCTL0 & TXEPT));
>     P3OUT ^= 0x01;
> //    P1OUT ^= 0x01;                      // Toggle P1.0 using
> exclusive-OR
>   }
> }

It looks like you have it set up correctly. I do notice that it looks 
like you're trying to run at 9600 baud, based on the values of UBR00 and 
UBR10. That being the case, the 250 KHz output you are getting sounds 
like you are running off of the default DCO frequency of approximately 
750 KHz. Take a look to make sure that the ACLK is selected in UTCTL0 
and not the SMCLK.

HTH,

Greg
Reply by owaiscareer ●March 14, 20062006-03-14
Thanks!
since uart0 did not work, i switched to uart1, by changing all 0s to
1s, i changed ssel0 to ssel1 mistakenly.  And yes, I did notice the
wrong baud rate in the meantime...TI tech support also got back to me,
the other problem was I was using a really old version of IAR
kickstart.  Both these changes when applied worked!
Thanks to everyone that helped!

--- In msp430@msp4..., Greg Maki <gmaki@...> wrote:
>
> owaiscareer wrote:
> > Hi Adriano,
> > 
> > I looked and implemented with no progress on UART0: please see below
> > (I now disable the UART state machine before initializing the
> > registers: UCTL0 |= SWRST)
> > 
> > ...curiously, moving the same code to UART1 makes it spit out data but
> > it is the wrong baud rate (250Khz) when I measure with the
> > oscilloscope, the data line is correctly toggling between 0 and 3.3V
> > though.  What gives?
> > 
> > Thanks,
> > Owais
> > 
> > void main(void)
> > {
> >   WDTCTL = WDTPW + WDTHOLD; //turn watchdog off
> > 
> >   UCTL0 |= SWRST;
> >    
> >   UCTL0 |= CHAR;   //char = 8 bits
> >   UTCTL0 |= SSEL0; //uclk = aclk (from 32.768 crystal); use auxiliary
> > clock source
> > 
> >   //N = brclk/baudrate = 32.768K/1200 = 27.31
> > //  UBR00 = 0x1B; //lsb(N) of baud rate register
> >   UBR00 = 0x03; //lsb(N) of baud rate register
> >   UBR10 = 0x00; //msb(N) of baud rate register
> >   UMCTL0 = 0x4A;//set modulation cntl register
> > 
> >  
> >   ME1 |= UTXE0 + URXE0;  //enable transmit and receive modules for
USART0
> >  
> >   UCTL0 &= ~SWRST;                          // Initialize USART
state
> > machine
> > 
> >   P3SEL |= 0x30;  //P3.4 P3.5, use alternate (UART) function 11000000
> >   P3DIR |= 0x10;  //P3.4 = output direction 01000000
> >   P3DIR &= ~0x20; // set bit 5 to low = input 1000000
> >   P3DIR |= 0x01;  //P3.1 toggle bit (output direction)
> >   for(;;)
> >   {
> >     TXBUF0 = 0xAA;  //send again...
> >     while(!(UTCTL0 & TXEPT));
> >     P3OUT ^= 0x01;
> > //    P1OUT ^= 0x01;                      // Toggle P1.0 using
> > exclusive-OR
> >   }
> > }
> 
> It looks like you have it set up correctly. I do notice that it looks 
> like you're trying to run at 9600 baud, based on the values of UBR00
and 
> UBR10. That being the case, the 250 KHz output you
are getting sounds 
> like you are running off of the default DCO frequency of approximately 
> 750 KHz. Take a look to make sure that the ACLK is selected in UTCTL0 
> and not the SMCLK.
> 
> HTH,
> 
> Greg
>
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