Send serial commands over GPIO on nRF52832

RE: Send serial commands over GPIO on nRF52832

awneil — Mon, 15 Apr 2019 08:21:07 GMT

Thanks for the feedback.

A good tip when working with any device like this is to always start by connecting it to a PC with a terminal program, and use that to manually send commands to it, and observe the results and the responses.

That way you can work out the correct commands & responses without the added complication of embedded hardware & software development.

Especially useful when you're not too familiar with the embedded target.

RE: Send serial commands over GPIO on nRF52832

ronpetit — Sat, 13 Apr 2019 21:01:50 GMT

Just to let anyone know, I solved the problem and it wasn't related to the nRF52 i was using the ASCII commands \r and \n for return and new line on sending the commands to the nextion and that make the screen not able to receive any further command, all I needed was to send the command clean, without anything else

RE: Send serial commands over GPIO on nRF52832

Jørgen Holmefjord — Fri, 12 Apr 2019 09:20:30 GMT

Did you use the same pins, or different ones? Events will depend on which UART implementation you are using. If you use the UART peripheral example in the SDK, uart_error_handle() will be called when events are received. Use your debugger to set a breakpoint in this function and see if it is being called.

RE: Send serial commands over GPIO on nRF52832

ronpetit — Thu, 11 Apr 2019 17:19:43 GMT

No, I do not have a logic analyzer, however I used the pin number 6 and 8 of the nRF52 DK to test the UART example with my own computer, and I can read exactly what I need to send to the screen, that's why I think the string are sent correctly, and I don't know how to get events from the UART peripheral, please If you have any other clue let me know, I will keep trying

RE: Send serial commands over GPIO on nRF52832

Jørgen Holmefjord — Thu, 11 Apr 2019 09:04:57 GMT

Have you checked the lines with a logic analyzer, to see if the expected strings are sent to the screen? Do the screen send any response back to the nRF? Do you get any events from the UART peripheral?

RE: Send serial commands over GPIO on nRF52832

ronpetit — Tue, 09 Apr 2019 20:21:32 GMT

Can you check please my answer to the awneil answer?, I'm stuck

RE: Send serial commands over GPIO on nRF52832

ronpetit — Tue, 09 Apr 2019 20:11:50 GMT

Hello, sorry for the late response, I'm really stuck over this, I already managed to get the uart example working over the USB cable I connect to the nRF52 DK, I can send and read the serial data, however, when trying to use my nextion screen nothing happens, you said that the MCU connect via 5V TTL serial, however over here https://www.itead.cc/wiki/NX4024T032 it says that the screen can recognize the 3.3V as a high, and I'm powering the screen with 5V from an external source, so what might be wrong?, do the TX from the screen transmit 5V and the nRF52832 gets errors?

About the 0xFF, those are endlines, I'm sending the ASCII text instruction followed by 0xFF three times, that's how it worked over the Nextion Editor debugger (A debugger for the screen).

I don't really know what can be wrong, I feel that the 5V TTL should not be a problem.

PD: I'm using the pins 23 as RX and 25 as TX on the nRF52 DK

RE: Send serial commands over GPIO on nRF52832

awneil — Fri, 05 Apr 2019 15:07:59 GMT

[quote userid="76009" url="~/f/nordic-q-a/45798/send-serial-commands-over-gpio-on-nrf52832"] a nextion TFT screen[/quote]

One of these: https://nextion.itead.cc/ ?

That page says:

"NEXTION display quickly connects to MCU via 5V TTL Serial"

Note that nRF52832 pins are not 5V tolerant.

[quote userid="76009" url="~/f/nordic-q-a/45798/send-serial-commands-over-gpio-on-nrf52832"] I need to send ... 0xFF three times so the screen will read the commands.[/quote]

Are you sure? The page also says:

"utilizes simple ASCII text based instructions"

0xFF would not normally be considered "ASCII text".

RE: Send serial commands over GPIO on nRF52832

Jørgen Holmefjord — Fri, 05 Apr 2019 14:05:04 GMT

Any GPIO that is not used by other peripherals on the DK can be used. P0.05-P0.08 is used for UART, P0.13-P0.20 is used for Buttons and LEDs, P0.21 is used for RESET, P0.00 and P0.01 is use for LF crystal, and P0.09 and P0.10 is used for NFCT. See the nRF52 DK User guide for more details.

RE: Send serial commands over GPIO on nRF52832

ronpetit — Fri, 05 Apr 2019 12:29:04 GMT

I think I didn't get the correct hit for a good UART example, I will follow the one you linked me.

If it would be better to use a different GPIO which one do you recommend?, or any GPIO will do?

RE: Send serial commands over GPIO on nRF52832

Jørgen Holmefjord — Fri, 05 Apr 2019 11:23:32 GMT

Hi,

The UART example is one of the recommended starting points for implementing UART connections to external devices. The documentation for how to test the example can be found here. Can you explain in more detail what it is you are not understanding? Note that P0.06 and P0.08 is by default connected to the on-board debug chip on the DK, to allow sending data through virtual COM port to PC. If you want to interface external device, it would be better to use different GPIOs.

Best regards,
Jørgen