UART unresponsive on custom board

RE: UART unresponsive on custom board

ovrebekk — Tue, 14 Jan 2020 13:46:36 GMT

Hi again

Ignore my comment with regards to flow control, I see now that you mention earlier that no flow control is used.

If you can share the example code you test on the DK I will test it on my side to see where the problem might be.

Best regards
Torbjørn

RE: UART unresponsive on custom board

ovrebekk — Tue, 14 Jan 2020 13:41:19 GMT

Hi Prasan

Sorry for the slow response, for the last month or so I have been out in travel and vacation.

Is hardware flow control enabled?

If it is communication can only occur when both the RTS and CTS lines are low.

It should be possible to re-assign the UART pins on the DK, even if the default configuration uses P0.08 and P0.06.

If you can confirm whether or not HWFC is used I can run a test on my own to see if I spot the same issue. Could you share the main.c file of your modified example?

Best regards
Torbjørn

RE: UART unresponsive on custom board

pdpro — Fri, 20 Dec 2019 02:55:59 GMT

Hi Torbjorn,

There is some weird behaviour of board I observed today. As per general assumption, I changed the pin on nRF52840 DK to p1.03 & p1.05 as these are unused pins to check the behaviour of UART. I checked the schematic files also and these pins are not connected for any other interfacing. Unfortunately, there is no sign of communication happening on these pins, I cross-checked by connecting logic analyser also.

I checked the schematic and found that pin P0.08 & P0.06 are connected through FSA2466UMX IC which is helping to see the communication through putty. This might be the reason that changing to any other pin is not working.

My custom board also doesn't have any pins hardwired for this communication. Please help me understand and resolve this issue.

Regards,

Prasan

RE: UART unresponsive on custom board

pdpro — Mon, 16 Dec 2019 00:46:58 GMT

I connected a US logic analyser on the pins and tried to check if something coming on bus. Unfortunately, there is no any activity on the corresponding bus. Do you think there is any major hardware issue, how custom board UART communication is tested? nRF52840 DK has UART pins hardwired, so data transmission can be directly seen on the USB port corresponding to USB cable connected to J2. I even checked on logic analyser and it is getting decoded properly. Does my custom board receives the data sent on J2 USB COM port?

RE: UART unresponsive on custom board

pdpro — Fri, 13 Dec 2019 03:52:37 GMT

Hi,

I am using basic UART example so there is no scope for TWI initialization.

I put TX pin in high drive mode in main program just after UART initialization like this:

int main(void)
{
    ...
    const app_uart_comm_params_t comm_params =
      {
          RX_PIN_NUMBER,
          TX_PIN_NUMBER,
          RTS_PIN_NUMBER,
          CTS_PIN_NUMBER,
          UART_HWFC,
          false,
#if defined (UART_PRESENT)
          NRF_UART_BAUDRATE_115200
#else
          NRF_UARTE_BAUDRATE_115200
#endif
      };

    APP_UART_FIFO_INIT(&comm_params,
                         UART_RX_BUF_SIZE,
                         UART_TX_BUF_SIZE,
                         uart_error_handle,
                         APP_IRQ_PRIORITY_LOWEST,
                         err_code);
    nrf_gpio_cfg(TX_PIN_NUMBER, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_CONNECT, NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_H0S1, NRF_GPIO_PIN_NOSENSE);

...
}

I also disabled flow hardware control from driver file. Still there is no sign of any communication.

I even tried to do loop back test but there is no success. Is UART communication necessary for sending ADC or any sensor data over BLE?

RE: UART unresponsive on custom board

ovrebekk — Thu, 28 Nov 2019 09:57:20 GMT

Have you made sure to remove the TWI initialization for those pins so that you don't have a conflict between the TWI and UART interfaces?

If you are using 2.2kOhm pull up resistors it is possible you have to configure the TX pin to use the high drive mode, or it might not be able to pull the lines low.
To set an output as high drive you can run the following command after enabling the UART:

nrf_gpio_cfg(TX_PIN_NUMBER, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_CONNECT, NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_H0S1, NRF_GPIO_PIN_NOSENSE);

Also, if you only have two pins available, how can you use RTS and CTS?
Is hardware flow control necessary, or could you disable this to reduce the IO requirement?

Best regards
Torbjørn

RE: UART unresponsive on custom board

pdpro — Wed, 27 Nov 2019 07:35:56 GMT

Attached the schematic as needed. I am trying to use pin 26 or 27 as it is having pull up resistor. Note that I have not mounted the sensor yet and thus unused pins.

Let me know which pins do you think would be best for UART communication. As already explained before, I only have these two pins 26 & 27 where I could connect some scope for testing and there is no any other exposed pin.

Ultimately I cannot use them for UART communication as these will be going to be used for TWI communication.

devzone.nordicsemi.com/.../Schema.pdf

RE: UART unresponsive on custom board

ovrebekk — Tue, 26 Nov 2019 08:03:39 GMT

Hi Prasan

Can you provide a schematic for your board?
What are the UART pins connected to?

Are you able to connect a scope to the pins to see what is happening on the bus?

As you say there is no limit on which of the GPIO pins can be used for UART, as long as they are not used for anything else.

Best regards
Torbjørn

RE: UART unresponsive on custom board

pdpro — Tue, 26 Nov 2019 02:38:26 GMT

As per kenneth reply on my question, I tried one GPIO pin with 2.2KOhm pull-up resistor which I tried to use for RXD. Still there is no sign of communication being established properly.