Hello all,

When no output was measured while testing to see if the UART TXD was writing characters out with the help of Kiel's CodeArchitect for a p89lpc935, I tried setting a value to SBUF and then checking the output via an LCD. Using a sample code as a base found on codearchitect.org, I have reached the current point and am not sure where to go from here.

SBUF is currently never set to the value passed into the uart_transmit() function. If anyone can help it would be greatly appreciated.

Thanks,


/****************************************************************
UART Program Code
***************************************************************/
include "reg932.h"
void main(){
uart_init();
forever{
uart_transmit('Z');
}
}

/*******************************************************************
DESC: Initializes UART for mode 1
Baudrate: 9600
RETURNS: Nothing
CAUTION: If interrupts are being used then EA must be set to 1
after calling this function
************************************************************************/
void uart_init
(
void
)
{
// configure UART
// clear SMOD0
PCON &= ~0x40;
SCON = 0x50;
// set or clear SMOD1
PCON &= 0x7f;
PCON |= (0 << 8);
SSTAT = 0x80;

// configure baud rate generator
BRGCON = 0x00;
BRGR0 = 0xD2;
BRGR1 = 0x04;
BRGCON = 0x03;

// initially not busy
mtxbusy = 0;

// set isr priority to 0
IP0 &= 0xEF;
IP0H &= 0xEF;
// enable uart interrupt
ES = 1;

} // uart_init

/***********************************************************************
DESC: UART Interrupt Service Routine
RETURNS: Nothing
CAUTION: uart_init must be called first
EA must be set to 1
************************************************************************/
void uart_isr
(
void
) interrupt 4 using 1
{
if (RI)
{
// clear interrupt flag
RI = 0;
} // if

if (TI)
{
// clear interrupt flag
TI = 0;
// no longer busy
mtxbusy = 0;
} // if

} // uart_isr

/***********************************************************************
DESC: Transmits a 8-bit value via the UART in the current mode
May result in a transmit interrupt if enabled.
RETURNS: Nothing
CAUTION: uart_init must be called first
************************************************************************/
void uart_transmit
(
unsigned char value // data to transmit
)
{

mtxbusy = 1;

while(mtxbusy){
SBUF = value;
LcdClear();
LcdWriteString("Writing SBUF Value");
if (SBUF != value){
LcdWriteCmd(0x0C0);
LcdWriteString("SBUF Value: ");
LcdWriteChar(SBUF);
LcdWriteString(" Not Equal to ");
LcdWriteChar(value);
}
}
} // uart_transmit

/***********************************************************************
DESC: Gets a received 8-bit value from the UART
RETURNS: Received data
CAUTION: uart_init must be called first
************************************************************************/
unsigned char uart_get
(
void
)
{
return SBUF;
} // uart_get