receive 9-bit data via UART1 using LPC1754?

[stijn_paesen]

Hello,

How to set up the UART1 to receive a 9-bit data (RS485) message for LPC1754?

1 start bit, 9 data bits, 1 stop bit

Is setting parity needed? I get every byte I receive an parity error?

Regards,
Stijn

I set:
UART_InitStruct->Baud_rate = 460800;
UART_InitStruct->Databits = UART_DATABIT_8;
UART_InitStruct->Parity = UART_PARITY_SP_1;
UART_InitStruct->Stopbits = UART_STOPBIT_1;

UART_FIFOInitStruct->FIFO_DMAMode = DISABLE;
UART_FIFOInitStruct->FIFO_Level = UART_FIFO_TRGLEV0;
UART_FIFOInitStruct->FIFO_ResetRxBuf = ENABLE;
UART_FIFOInitStruct->FIFO_ResetTxBuf = ENABLE;

rs485cfg.AutoDirCtrl_State = ENABLE;
rs485cfg.DirCtrlPin = UART1_RS485_DIRCTRL_DTR;
rs485cfg.DirCtrlPol_Level = SET;
rs485cfg.DelayValue = 50;
rs485cfg.NormalMultiDropMode_State = ENABLE;
rs485cfg.AutoAddrDetect_State = DISABLE;
//rs485cfg.MatchAddrValue = 0;
rs485cfg.Rx_State = ENABLE;

[kerryzhou]

Hi Stijin,

    LPC175X can't support 9 bit data size, please check the user manual:

UART1 module can't support the 9 bits data size, just 5.6.7 and 8 bits.

Wish it helps you!

Have a great day,
Kerry

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[stijn_paesen]

Hello,

Yesterday I managed to receive data and address bytes

            UART_InitStruct->Baud_rate = 454545;

            UART_InitStruct->Databits = UART_DATABIT_8;

            UART_InitStruct->Parity = UART_PARITY_NONE;

            UART_InitStruct->Stopbits = UART_STOPBIT_1;

            rs485cfg.AutoDirCtrl_State = ENABLE;

            rs485cfg.DirCtrlPin = UART1_RS485_DIRCTRL_DTR;

            rs485cfg.DirCtrlPol_Level = SET;

            rs485cfg.DelayValue = 50;

            rs485cfg.NormalMultiDropMode_State = ENABLE;

            rs485cfg.AutoAddrDetect_State = DISABLE;

            rs485cfg.MatchAddrValue = 0;

            rs485cfg.Rx_State = ENABLE;

bytes with 9^th bit 0, data bytes are received correctly

bytes with 9^th bit 1, address bytes are received with parity error, but can be read when handling the error

Not the most nice way but it works.

Regards,

Stijn

[kerryzhou]

HI Stijin,

   Thank you for your updated information. Actually, it is just caused by the hardware can't support the 9 bit data directly.

  So, if you can receive the data correctly, just have parity error, I think you can check the error, if it is the parity error,  ignore it.

  If you still have question about it, please kindly let us know.

Have a great day,
Kerry

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