topic Re: UART TXDATA last byte missing in LPC Microcontrollers

UART TXDATA last byte missing

athmesh_n — Tue, 15 Jan 2019 05:33:17 GMT

Data from UART is missing last byte using the following code snippet.

rs485_tx_mode();                                                    //Setting as Transmission
for(mb=0;mb<u8ModbusADUSize;mb++)               //u8ModbusADUSize = 8
{
  while(~LPC_USART0->STAT & (1<<3));
  LPC_USART0->TXDATA = u8ModbusADU[mb];
}
while(~LPC_USART0->STAT & (1<<3));
rs485_rx_mode();                                                 //Setting as Reception

u8ModbusADUsize is 8, and the u8ModbusADU[7] is missing during continuous run. But while debugging step-by-step we are getting the full output including u8ModbusADU[7].

Processor : LPC1517

IDE : MCUXpresso

Clock : Internal Clock

Thanks and Regards,

Athmesh Nandakumar

Re: UART TXDATA last byte missing

darius_b — Wed, 16 Jan 2019 15:37:14 GMT

Hi Athmesh,

Possible you lost last byte when switch into rx mode.

Try insert delay 1ms.before rs485_rx_mode function.

BR.

Darius Babrauskas

Re: UART TXDATA last byte missing

athmesh_n — Thu, 17 Jan 2019 05:24:53 GMT

Thanks

Re: UART TXDATA last byte missing

kerryzhou — Thu, 17 Jan 2019 05:42:12 GMT

Hi ATHMESH NANDAKUMAR,

Please modify your code like this:

rs485_tx_mode(); //Setting as Transmission

for(mb=0;mb<u8ModbusADUSize;mb++)               //u8ModbusADUSize = 8
{
  while(~(LPC_USART0->STAT & (1<<2)));
  LPC_USART0->TXDATA = u8ModbusADU[mb];
}

while(~(LPC_USART0->STAT & (1<<3)));
rs485_rx_mode(); //Setting as Reception

If you still have problems, just add a small delay above rs485_rx_mode();

Please try it again.

Any updated information, just let me know.

Have a great day,
Kerry

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