Reply by aaronedsinger ●August 14, 20032003-08-14
Hello. I'm trying to use the SCI1 on my 56F807 to do a simple 9-bit
protocol address-wakeup communication. However, I seem to be having
problems with getting the baud rate correct. With the following code:

----------------
SciConfig.SciCntl = SCI_CNTL_WORD_9BIT | SCI_CNTL_PARITY_NONE |
SCI_CNTL_LOOP_NO| SCI_CNTL_ENABLE_IN_WAIT| SCI_CNTL_WAKE_BY_ADDRESS;

SciConfig.SciHiBit = SCI_HIBIT_0;
SciConfig.BaudRate = SCI_USER_BAUD_RATE_1; //def as 10

Sci9FD = open(BSP_DEVICE_NAME_SCI_1, O_RDWR | O_NONBLOCK, &
(SciConfig));
ioctl( Sci9FD, SCI_DATAFORMAT_EIGHTBITCHARS, NULL );

/* NonBlocking Read and Write */
ioctl( Sci9FD, SCI_CALLBACK_EXCEPTION, NULL ); //no error handling
ioctl( Sci9FD, SCI_CALLBACK_RX,sci_9bit_rx );
ioctl( Sci9FD, SCI_CALLBACK_TX, sci_9bit_tx);

sci_rx_len=1; //callback on every rx char
ioctl( Sci9FD, SCI_SET_READ_LENGTH, (void *)&sci_rx_len );

------------------
I get a baud rate that is far too low for 250,000 baud, which I
should get with my IP Bus Freq@,000,000 and SCI_USER_BAUD_RATE_1.

However, If I make a subsequent call:

periphMemWrite(10, &ArchIO.Sci1.BaudRateReg);

The rate looks correct and the SCI seems to receive bytes ok. However
it fails to identify the address bytes (set by the 9th bit). I sniff
for these by issuing:

ioctl( Sci9FD, SCI_CMD_WAIT, NULL );

and when I next enter my sci rx callback, I assume that the received
byte is an address byte. However, this rarely happens.

Does anyone have any insight or experience with this? Thank you.

-Aaron

Aaron Edsinger
Living Machines Group
MIT Artificial Intelligence Lab