TMS320F280049: UART autobaud rate detection

Kevin Chen31

Prodigy 230 points

Part Number: TMS320F280049

Hi C2K experts,

I am trying to use auto baud rate detection (F280049), however,

the program is stuck at below statement, even I had sent 'a' ('A').

while(SciaRegs.SCIFFCT.bit.ABD != 1) {}

I am sure the RX, TX pins are correct. The host baud rate is 9600.

Here is my code:

void SCIA_AutobaudLock(void)
{

Uint16 byteData;

SciaRegs.SCICCR.all = 0x0007;

SciaRegs.SCICTL1.all = 0x0003;

SciaRegs.SCICTL2.all = 0x0000;

SciaRegs.SCICTL1.all = 0x0023;

// Reset
SciaRegs.SCIFFTX.bit.SCIRST = 1;

//----- SCI Reset -----//
SciaRegs.SCICTL1.bit.SWRESET = 0;
SciaRegs.SCICTL1.bit.SWRESET = 1;
//---------------------//

// Must prime baud register with >= 1
SciaRegs.SCIHBAUD.all = 0x0000;
SciaRegs.SCILBAUD.all = 0x0001;

// Prepare for autobaud detection
// Set the CDC bit to enable autobaud detection
// and clear the ABD bit
SciaRegs.SCIFFCT.bit.CDC = 1;
SciaRegs.SCIFFCT.bit.ABDCLR = 1;

// Wait until we correctly read an
// 'A' or 'a' and lock
while(SciaRegs.SCIFFCT.bit.ABD != 1) {}

// After autobaud lock, clear the ABD and CDC bits
SciaRegs.SCIFFCT.bit.ABDCLR = 1;
SciaRegs.SCIFFCT.bit.CDC = 0;

while(SciaRegs.SCIRXST.bit.RXRDY != 1) { }

byteData = (Uint16)SciaRegs.SCIRXBUF.bit.SAR; //SciaRegs.SCIRXBUF.bit.RXDT;
SciaRegs.SCITXBUF.bit.TXDT = byteData;

return;

}

May I have your comment about this?

Thanks,

over 5 years ago

0 Devin Cottier over 5 years ago

TI__Guru 60865 points

Hi Kevin,

What GPIOs are you using for SCI-A? Are you using a virtual COM port or a physical serial connection? If it is a physical serial connection, what transceiver are you using? Either way, have you run the SCI echoback example (with pre-specified baud) to verify the hook-up and that 'a' is transmitted from the host and received by the MCU as expected?

0 Kevin Chen31 over 5 years ago in reply to Devin Cottier

Prodigy 230 points

Hi Devin,

I am using 64pin package, the GPIO I am using is GPIO28(RX)/pin2, GPIO29(TX)/pin1.

I use physical serial connection, the transceiver is SiliconLab CP210x.

Yes, I had tested SCI echoback example and also SCI firmware update function without error.

Thanks,

0 Devin Cottier over 5 years ago in reply to Kevin Chen31

TI__Guru 60865 points

Hi Kevin,

I don't see anything obviously wrong with your setup or code.

One debug activity might be to pause execution in the spin-wait loop that is waiting for auto-baud detect. You can then go into the expressions window in the debugger and check some of the following:

Status of SCIRXST register. Are any of the error flags set such as BRKDT?

Status of the other SCI configuration registers, in particular you may want to verify that the settings that should have been written in the code have actually made it to the SCI registers. e.g. check that these writes actually made it into the registers:

SciaRegs.SCICCR.all = 0x0007;

SciaRegs.SCICTL1.all = 0x0003;

SciaRegs.SCICTL2.all = 0x0000;

SciaRegs.SCICTL1.all = 0x0023;

(if they don't match, the likely culprits would be a missing 'EALLOW' or some other code that later re-initializes the settings accidentally)

You may also want to check the other basic system configurations at that point too (PLL and clocking, LSPCLK divider, etc.)