CC1110 UART Baud Rate Issue

SteveSmith

I'm trying to set the baud rate on a CC1110 to 115200 but it always comes out at 57600. I am using a 27MHz crystal and have adjusted U1BAUD to 24 from the suggested 34 for a 26MHz crystal. I've also checked and the PARTNUM register reads back 0x01. Below is the code. I can make it go to 115200 by changing U1GCR to 13 but I don't know why the speed seems to be 1/2 of what I think it should be.

while ((U1CSR & U1CSR_ACTIVE) != 0) { } // Ensure we're not active when baud is changed
U1BAUD = 24; // BAUD will be set to 115,200 for now
U1GCR = 12;
U1UCR = U1UCR_STOP; // Single 'hi' stop bit
U1CSR = U1CSR_MODE | U1CSR_RE; // Enable UART1 as RS-232

for (i=0; i<=MRFI_MAX_FRAME_SIZE; i++)
txmsg.frame[i] = 0x00;
PKTLEN = txmsg.frame[0] = PACKET_LENGTH; // length
txmsg.frame[ 1] = flashDeviceAddr[ 0]; // My unique ID num
txmsg.frame[ 2] = flashDeviceAddr[ 1];
txmsg.frame[ 3] = flashDeviceAddr[ 2];
txmsg.frame[ 4] = flashDeviceAddr[ 3] | GATEWAY_FLAG;
U1DBUF = 0x55; // Dummy character just to get the RS-232 queue moving

over 11 years ago

0 Siri over 11 years ago

TI__Guru* 86241 points

Have you made sure that your system clock runs on the crystal frequency and not crystal frequency/2. If you have not change CLKCON.TICKSPD the system clock runs on crystal freq./2 and. The F in the baud rate formula is the system clock freq. and not the crystal freq.

Siri

0 SteveSmith over 11 years ago in reply to Siri

Intellectual 360 points

I thought I did but you are correct. I found that you have to set CLKCON.OSC to 0 before trying to set CLKCON.CLKSPD to 000. Even though I was doing CLKCON=0xA0, CLKSPD would be 001 if OSC was 1.

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CC1110 UART Baud Rate Issue