UART1 Data register problem

Hello Aish,

Thanks for the content of the Data Register. In the value 0x500 the lower byte is the data and the upper nobble showing 0x5 is indicative that there is a Break and Framing Error. In case of a framing error the data shall not be written as the UART reciever is not sure of the frame itself.

Please check the baud rate settings, number of stop, parity bits and if possible put it on the scope or LA to see how back-2-back transfers are being done by the UART source to the TM4C123.

Regards

Amit

Hi Amit,

// Configure UART1 to 38400 baud, 8N1 format (must be 3 clocks from clock enable and config writes)
UART1_CTL_R = 0; // turn-off UART1 to allow safe programming
UART1_CC_R = UART_CC_CS_SYSCLK; // use system clock (40 MHz)
UART1_IBRD_R = 65; // r = 40 MHz / (38400), set floor(r)=21, where N=16
UART1_FBRD_R = 7; // round(fract(r)*64)=7 // 64 coz fractional data
UART1_LCRH_R = UART_LCRH_WLEN_8; // configure for 8N1 w/o FIFO
UART1_CTL_R = UART_CTL_TXE | UART_CTL_RXE | UART_CTL_UARTEN; // enable TX, RX, and module
UART1_IM_R = UART_IM_RXIM;
NVIC_EN0_R = 1<<6;//(22-16);

This is how I configured my UART1, and I am sending 9 bit data, including the parity bit, 1 start bit and 1 stop bit,

my IBRD is 65, but in the IBRD register it is 41.

I have no clue how the register is reading something else :(

Amit,

Yes, the format is the same as you said and it is the same in the transmitter side.I finally figured out the issue, I realized my PCB circuit which I built for the class project might be a problem, I tried using a different board from my friend. And I finally got the output. And I would definitely follow your advice. Thanks a lot !

Hello Aish,

I am not tolally convinced even though it started working. The reason is that having a parity bit in the format implies that that the Parity enable has to be set in the LCRH register. In the original code you sent that is missing,

Regards

Amit

Amit,

I am setting EPS bit in this part of my program, I have attached that snippet for your reference,

void sendAddress(uint16_t data){
UART1_LCRH_R=0;
UART1_LCRH_R = UART_LCRH_WLEN_8 | UART_LCRH_SPS | UART_LCRH_PEN;
while(UART1_FR_R & UART_FR_TXFF);

UART1_DR_R =data;
puts("in send address");
waitMicrosecond(10000);
checksum = checksum + data;
cnt++;
}
void sendData(uint16_t data)
{
UART1_LCRH_R = UART_LCRH_WLEN_8 | UART_LCRH_SPS | UART_LCRH_PEN | UART_LCRH_EPS;
while(UART1_FR_R & UART_FR_TXFF);

UART1_DR_R = data;
puts("in send data");
waitMicrosecond(10000);
checksum += data;
cnt++;
}
void send485(uint16_t dest_addr,uint16_t cmd, uint16_t channel, uint16_t size, uint16_t data)
{
DEN = 1;
puts("in send485");
sendAddress(dest_addr);
//waitMicrosecond(10000);
sendData(0);
sendData(txseqid);
//waitMicrosecond(1000);
sendData(cmd);
sendData(channel);
sendData(size);
if(size==1){
sendData(data);
}
sendData(checksum);
while(UART1_FR_R & UART_FR_TXFF);
DEN = 0;
}

and I am declaring the variables globally.

Hello Aish,

Now that convinces me as the first code post did not have it.

BTW, what was the HW problem on the PCB, have you figured that out.

Regards

Amit

Amit,

No, I am yet to go to the lab to check the connectivity. I would post here as soon as I correct it.

Regards,

Aishu

Along w/pcb & parity issues - what fun awaits this fellow when he must (manually) fill out multiple Gov't forms - each demanding his (full) name.  (duly noted was Amit's (friendly) "u-less" abbreviation)   (antidisestablishmenttarianism  anyone?)

Can only imagine teacher/instructor's (grade book) Excel "column width" - struggling to accommodate...