UART on ARM9

Dan:

I have a sneaking suspicion that you're right! I'm looking at the ST document 12274.pdf on page 39 and it looks like I definitely need to set P3.1 to "Alternate Output 2". That said, page 78 in ST document 112126.pdf says to set bits 3:2 to 1 and 0 respectively (0x08). I'll check it out tonight and revert in the A.M.

Thanks so much!

-=Rich=-

Dan:

I have a sneaking suspicion that you're right! I'm looking at the ST document 12274.pdf on page 39 and it looks like I definitely need to set P3.1 to "Alternate Output 2". That said, page 78 in ST document 112126.pdf says to set bits 3:2 to 1 and 0 respectively (0x08). I'll check it out tonight and revert in the A.M.

Thanks so much!

-=Rich=-

All:

Dan made the call when he spotted that I had transposed nibbles. After making the suggested correction the code ran just fine.

The following is the working code (for the benefit of anyone else that was having similar problems)

//*************************** TEST.C ************************************
// Auth:    R. McCoy
// Date:    10/5/2006
// Gist:    Blinks LEDS on port 7 of Keil MCBSTR9 board. Also spits a
//          character ('A') out of COM1 (UART0).
// Note:    It appears that there is an error in the documentation on page 78 of
//                  ST Manual UM0216 (STR91x Reference manual). The SCU_GPOINn register
//                  documentation makes no sense whatsoever. Only 8 bits are shown...not
//          the 16 bits that should be depicted. Also, why does the table jump from
//          pin3 to pin7 (going right to left)?
// Stat:    Works fine.
//
// Targ:    Using the Keil MCBSTR9 Demo Board:
//          COM1 is connected to pins P3.0 (Rx) and P3.1 (TX)
//          COM2 is connected to pins P3.2 (Rx) and P3.3 (TX)
//          Both ports are set up as DCE. This means you DON'T need a Null Modem
//          cable. A DB-9 straight-thru works just fine.
//
//          Per Table 4 of the Str91xF (ARM966E-S) datasheet (STR912FW44.pdf):
//          UART0 Rx is Alt Input 1 on GPIO_3.0
//          UART0 Tx is Alt Output 2 on GPIO_3.1
//
//          Board is operating at 48 Mhz and the BRDi and BRDf registers
//          are set up to generate a baudrate of 115,200.
//
//  Warn:   This file does not contain "production" code. It is written for
//          testing purposes only. AS A RESULT, NEITHER RICHARD MCCOY NOR HIS EMPLOYER
//          SHALL NOT BE HELD LIABLE FOR ANY DIRECT, INDIRECT OR CONSEQUENTIAL DAMAGES
//          WITH RESPECT TO ANY CLAIMS ARISING FROM THE CONTENT OF SUCH SOFTWARE AND/OR
//          THE USE MADE BY OTHERS OF THE CODING INFORMATION CONTAINED HEREIN IN
//          CONNECTION WITH THEIR PRODUCTS.
//***********************************************************************

#include <91x_lib.h>
#include "LCD.h"
int sendchar(int ch);
int retval;

void wait (void){   /* Wait function                    */
  long d=950000L;   /* 950,000 gives a delay of about 1 sec. */
  while (d--);      /* Only to delay for LED flashes    */
}
int main (void) {
  unsigned int i;
  SCU->GPIOOUT[7]  = 0x5555;    /* P7.0..7 output - mode 1          */
  GPIO7->DDR       = 0xFF;      /* P7.0..7 Outputs (LED Data)       */

  /* LCD Setup......................................................*/
  GPIO8->DDR       = 0xFF;      /* P8.0..7 Outputs (LCD Data)       */
  GPIO9->DDR       = 0x07;      /* P9.0..2 Outputs (LCD Control)    */

 /* UART0 Setup.....................................................*/

   SCU->GPIOOUT[3] &= 0xFFF3;   /* Enable UART0_TX (COM1) connected to P3.1  */
                                /* by setting bits 3 & 2 to 0 first */
   SCU->GPIOOUT[3] |= 0x0008;   /* then by setting bit 3 to 1  */
                                                                /* this sets GPIOOUT[3] to "Alternate Output 2" */
                                /* see page 78 of ST Microelectronics Document */
                                /* UM0216 (12126.pdf) for info on this register */
                                /* see page 39 of ST Microelectronics 12274.pdf- */
                                /* STR91xF Data Sheet for information on alternate */
                                /* pin functions */

   SCU->GPIOIN[3]  |= 0x01;          /* Enable UART0_RX (COM1) connected to P3.0             */
                                                                /* by setting bit 0 to 1                                */
                                                                /* this sets GPIOIN[3] to "Alternate Input 1" */

                                /* Baud rate integer and fractional divisors were */
                                /* calculated based on the Baud Rate Clock being */
                                /* set to fMSTR (as opposed to fMSTR/2).         */

   UART0->IBRD = 0x1A;          /* Integer divider for 115kBaud */
   UART0->FBRD = 0x03;          /* Fractional divider           */
   UART0->LCR  = 0x0060;        /* 8 bits, no Parity, 1 Stop bit, FIFO disabled */
   UART0->CR   = 0x0301;        /* Enable UART, Receive Enable, Transmit Enable */

  lcd_init();
  lcd_clear();
  lcd_print (" TEST.C  ");      /* this line of code works as expected */
  set_cursor (0, 1);
  lcd_print ("  October 5, 2006  "); /* this line of code works as expected*/
  retval=sendchar('A');             /* This function returns */

  for (i = 0; i < 5; i++) wait();    /* Wait for initial display         */
  while (1) {                        /* Loop forever                     */
      int n=0;
      for(n=0x01;n<=0xFF;n<<=1)             /* scroll thru all eight LEDS                */
          {
          GPIO7->DR[0x3FC] = n;          /* Turn on LED ...this code works   */
      wait();                        /* Delay                            */
          retval=sendchar('A');              /* This function returns */
      }
  }
}

int sendchar (int ch)  {
   /* Debug output to serial port. */

   if (ch == '\n')  {
      while (!(UART0->FR & 0x0080));
      UART0->DR = '\r';
   }
   while (!(UART0->FR & 0x0080));
   return(UART0->DR = ch);


}

I should add that it took some time to figure out that several registers must be modified in the ST91x.s startup file. In particular were the: 1.) Clock control register (SCU_CLKCNTR) 2.) Peripheral Gate Control register (SCU_PCGR1) 3.) Peripheral Reset register (SCU_PRR1) If you don't have these set correctly, the UART won't work. I strongly suggest using the "Configuration Wizard" to modify your startup file. But, by all means, read the docs as well. Good Luck to all and a special thanks to Dan Henry. He's the one responsible for my still having some hair left! -=Rich=-

That's great news Rich! Thanks for closing the loop and for the acknowledgement.