Issue wih UART1 and SD card bootloader

Hi dear Keil fellows,

I am developping a SD card bootloader based on the app note AN10835: LPC2000 Secondary bootloader. I don't need the menu and the command set to match the requirements of my application, but I think that displaying messages on the UART is a good way to get an easy debug monitoring. To achieve this goal I use the retarget.c and serial.c files provided with the app note but I am not able to get any frame I am supposed to send on my terminal.

I made many in-depth searchs over the inernet and in the LPC23xx user manual without success. I've seen few errors in the init_serial function so I modified it to match NXP's instructions.

The original init_serial:

/*----------------------------------------------------------------------------
 *       init_serial:  Initialize Serial Interface
 *---------------------------------------------------------------------------*/
/* init UART1, 115200/8/N/1, suppose PCLK=12MHz,  */
void init_serial () {
   /* Initialize the serial interface */

   /* Configure UART1 for 115200 baud. */
   PINSEL0 &= ~0xC0000000;
   PINSEL0 |=  0x40000000;                   /* Enable TxD1 pin              */
   PINSEL1 &= ~0x00000003;
   PINSEL1 |=  0x00000001;                   /* Enable RxD1 pin              */

   U1LCR = 0x83;                             /* 8 bits, no Parity, 1 Stop bit*/
   U1DLL = 3;                                /* for 12MHz PCLK Clock         */
   U1FDR = 0x67;                             /* Fractional Divider           */
   U1LCR = 0x03;                            /* DLAB = 0                     */
}

The one I use now:

/*----------------------------------------------------------------------------
 *       init_serial:  Initialize Serial Interface
 *---------------------------------------------------------------------------*/
/* init UART1, 115200/8/N/1, suppose PCLK=12MHz,  */
void init_serial () {
   /* Initialize the serial interface */

   /* Configure UART1 for 115200 baud. */
   PINSEL0 &= ~0xC0000000;
   PINSEL0 |=  0x40000000;                   /* Enable TxD1 pin              */
   PINSEL1 &= ~0x00000003;
   PINSEL1 |=  0x00000001;                   /* Enable RxD1 pin              */

   U1LCR = 0x83;                             /* 8 bits, no Parity, 1 Stop bit*/
   U1DLL = 4;                                /* for 12MHz PCLK Clock         */
   U1FDR = 0x85;                             /* Fractional Divider           */
   U1LCR &= 0x7F;                            /* DLAB = 0                     */
}

NB: Those values are from LPC23xx user manual page 455.

I was suspecting an issue with the retargeting of printf so I made a little funcion I called uprintf to not call printf.

/*----------------------------------------------------------------------------
 *       uprintf:  Print a string on Serial Port
 *---------------------------------------------------------------------------*/
void uprintf ( const char *buf , char len )
{
        for(  ; len ; len--) sendchar (*buf++);
}

I use this function in combination with sprintf:

char len;
char buf[128];

len = sprintf(buf, "\n> Initializing SD/MMC Card : ");
uprintf(buf, len);

Even with this method I don't have anything on my terminal. I managed to monitor the TXD1 pin with an oscilloscope but the pin remains tied to high level so I ask to know if you guys have any idea of what is going on or what I am doing wrong ?

My target is a LPC2388 and I develop with µvision 4.02 and RL-ARM 3.4 if it can help.

Thanks in advance for your help :)

Kind regards.