UART for NRF52832_AB on Custom Board

RE: UART for NRF52832_AB on Custom Board

Jared — Mon, 08 Jan 2024 10:23:54 GMT

[quote user="liyuyang702"]

yes, we use the 32MHz crystal model ABM3-32.000MHZ-D2Y-T, its datasheet is as below:

ABM3 (abracon.com)

[/quote]

Looking at the datasheet for the crystal, I can see that the load capacitance is 18 pF:

That is outside of spec.

regards

Jared

RE: UART for NRF52832_AB on Custom Board

hmolesworth — Fri, 05 Jan 2024 23:38:21 GMT

Typically the Tx pin requires a transmit such as app_uart_put('H'); where are you making printf() use the uart?

RE: UART for NRF52832_AB on Custom Board

liyuyang702 — Fri, 05 Jan 2024 20:23:31 GMT

Yes, I used the code from the SDK as you said, the board definition is the same pca10040.h,

#define RX_PIN_NUMBER  8
#define TX_PIN_NUMBER  6
#define CTS_PIN_NUMBER 7
#define RTS_PIN_NUMBER 5
#define HWFC           false

while I changed the main code to make the RX pin unconnected:

    bsp_board_init(BSP_INIT_LEDS);

    const app_uart_comm_params_t comm_params =
      {
          UART_PIN_DISCONNECTED,
          TX_PIN_NUMBER,
          RTS_PIN_NUMBER,
          CTS_PIN_NUMBER,
          APP_UART_FLOW_CONTROL_DISABLED,
          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);

    APP_ERROR_CHECK(err_code);

    printf("\r\nUART example started.\r\n");

    while (true)
    {
			printf("\r\nUART_running.\r\n");
			printf("\r\n1\r\n");
			printf("\r\n2\r\n");
			printf("\r\n3\r\n");
			printf("\r\n4\r\n");
    }

When I use the debug mode each 'printf' can be executed but there is no output at the TX pin.

RE: UART for NRF52832_AB on Custom Board

hmolesworth — Tue, 02 Jan 2024 16:56:05 GMT

I assume you are using this project:

.\nRF5_SDK_17.1.0_ddde560\examples\peripheral\uart\pca10040\blank\

Have you changed the default board definition?

 Directory of .\nRF5_SDK_17.1.0_ddde560\components\boards
pca10040.h
#define RX_PIN_NUMBER  8
#define TX_PIN_NUMBER  6
#define CTS_PIN_NUMBER 7
#define RTS_PIN_NUMBER 5

Maybe share the uart init code and the pin definiton you are using

RE: UART for NRF52832_AB on Custom Board

liyuyang702 — Tue, 02 Jan 2024 16:37:13 GMT

Thank you for the suggestion, I tried setting both RX and TX to the same pin but still get an error during initialization. Actually, later I tried setting the RX to UART_PIN_DISCONNECTED, it does not enter the error handler anymore but the printf function does not send out any message at the TX pin. If you have any idea about this please let me know. Thank you!

RE: UART for NRF52832_AB on Custom Board

hmolesworth — Mon, 25 Dec 2023 16:31:46 GMT

Possibly the pin has no external pull-up so requires an internal pull-up if the uart is started with no external connection to the uart Rx pin. If the pin starts low it will “see” a start bit, 8 low data bits but no high stop bit and so will generate a phantom framing error possibly before the handler is registered, hence a hard fault

Enable the pull-up on the Rx pin both before and after init() to be safe, some SDK versions are susceptible to this more than others. To test functionality you can set the Rx pin to be the same as the Tx pin, easy with bare metal, then the Rx input will echo the Tx output - this is an internal loop back, useful for testing though not supported by Nordic documentation

RE: UART for NRF52832_AB on Custom Board

liyuyang702 — Sat, 23 Dec 2023 21:34:14 GMT

Hi Jared,

yes, we use the 32MHz crystal model ABM3-32.000MHZ-D2Y-T, its datasheet is as below:

ABM3 (abracon.com)

and the 18pF capacitor are the parallel load capacitors, the model is CC0603JPNP09BN180, it is the one below:

UPY-GP_NP0_16V-to-50V_18.pdf (yageo.com). The 32.768kHz crystal ECS-.327-12.5-34B-TR: ecx-31b.pdf (ecsxtal.com), the 12pF cap is also the load parallel capacitor 0603N120J500CT: WTC_MLCC_General_Purpose_ASBC (passivecomponent.com)

I tried with breakpoints and it enters 'nrf_drv_uart_rx(&app_uart_inst, rx_buffer,1);' in the initializtion and then gets the error code 0x00000010 with error_info 0x20001FC8.

Thank you again for your help!

Yuyang

RE: UART for NRF52832_AB on Custom Board

Jared — Tue, 19 Dec 2023 08:29:51 GMT

Hi,

The external crystal is not necessary for the LFCLK, but then you have to configure your project to use the internal RC oscillator instead.

[quote user="liyuyang702"]we use the 32MHz crystal with 18pF load capacitance.[/quote]

Are you loading the crystal with 18 pF parallel capacitors or is the internal capacitance of the crystal 18 pF? Can you share the datasheet and full part number of the crystal that you're using?

[quote user="liyuyang702"]The debug mode in Keil shows it run into the HardFault_Handler.[/quote]

Can you use breakpoints and see how far the program reach in the UART sample before it enters the hardfault_handler?

regards

Jared

RE: UART for NRF52832_AB on Custom Board

liyuyang702 — Sat, 16 Dec 2023 01:59:24 GMT

Actually I added the 32.768KHz crystal, but the result does not change. The debug mode in Keil shows it run into the HardFault_Handler. The TX pin is pulled up to 3.3V, just no message was sent out. The crystal has a shunt capacitance of 1.05pF and the load capacitor is 12pF.

RE: UART for NRF52832_AB on Custom Board

liyuyang702 — Fri, 15 Dec 2023 15:31:26 GMT

Hi Jared,

Thank you for your reply! we do not place the low frequency crystal, we use the 32MHz crystal with 18pF load capacitance. Would the low freq. crystals be necessary? We have the place for a 32kHz crystal and 12pF load cap, we can add the components if it is a must.

Yuyang

RE: UART for NRF52832_AB on Custom Board

Jared — Fri, 15 Dec 2023 10:21:45 GMT

Hi,

[quote user=""] (The project is under the 'blank' directory, so I am thinking it means no boot loader needed).[/quote]

correct, and no softdevice,

Do you also have a low frequency crystal on the board? If so, what is the internal capacitance of the crystal and what size is the parallel load capacitors of the crystal?

regards

Jared