Unable to receive on Rx pin because Tx is always high.

[Shubham]

I have a custom board. It has its Tx and Rx combined into one wire bus. I am able to transmit data on the bus. But I am unable to receive any data on the board. This is because of circuit design.

In order to receive data I thought of disconnection the Tx pin when I am done transmitting the data. I did it by adding some code in `$SDK_ROOT/modules/nrfx/hal/nrf_uart.h`.

__STATIC_INLINE void nrf_uart_tx_pins_disconnect(NRF_UART_Type * p_reg)
{
#if defined(UART_PSEL_TXD_CONNECT_Pos)
    p_reg->PSEL.TXD = NRF_UART_PSEL_DISCONNECTED;
#else
    p_reg->PSELTXD = NRF_UART_PSEL_DISCONNECTED;
#endif
}

I thought of calling this function when I am done transmitting and want to receive data. This is works partially.

When I transmit and disconnect tx pin then I do not receive any data. But If I do not send any data and directly try to receive it works.

I want both way communication.

Is there anything to turn off Tx completely and just wait for receive, and when I want to transmit I enable the Tx and starts sending.

[hmolesworth]

From the manual "PSEL.RXD, PSEL.RTS, PSEL.RTS and PSEL.TXD must only be configured when the UARTE is disabled.". The Uart has to be disabled before changing the Tx pin then re-enabled.

[Shubham]

I am doing all the actions between `nrf_uart_disable` and  `nrf_uart_enable`.

[hmolesworth]

So you have this, right? You sure you are turning the pin back to an input as well as disconnecting from the Uart?

  nrf_uart_disable();
  p_reg->PSEL.TXD = NRF_UART_PSEL_DISCONNECTED;
  // Pin now disconnected from Uart, but it's still an output pin so must also turn off output drivers
  nrf_gpio_cfg_default(p_reg->PSEL.TXD);
  nrf_uart_enable();

[Shubham]

I am calling `nrf_uart_tx_pins_disconnect` between `nrf_uart_disable` and `nrf_uart_enable`

__STATIC_INLINE void nrf_uart_tx_pins_disconnect(NRF_UART_Type * p_reg)
{
    nrf_gpio_pin_clear(17);
#if defined(UART_PSEL_TXD_CONNECT_Pos)
    p_reg->PSEL.TXD = NRF_UART_PSEL_DISCONNECTED;
#else
    p_reg->PSELTXD = NRF_UART_PSEL_DISCONNECTED;
#endif
}

Let me try turning that pin to an input.