libuarte: Connection between NRF9160dk and NRF52840

[Brett]

Hi,

If there is already a FAQ, Code or support ticket that I missed, I am more than happy to read it.  I have done a number of searches but cant quite get to what I am looking for.

Setup:
I am trying to get communications between the52840 and 9160 on the 9160DK, using libuarte.  I am using zephyr on the 9160 side an the  nrf-sdk on the 52840 side (as I need ANT+).

A few articles I read were using uart1 for this type of communications, so I cut/paste what was in there.  From what I could gather, a way to do this was to use the MCU_IF with pins 17/18 (9160) => 17/20 (52840)

9160 (.overlay file):

&uart1 {

compatible = "nordic,nrf-uarte";

status = "okay";

current-speed = <115200>;

hw-flow-control;

rx-pin = <17>; /* <&interface_to_nrf52840 0 0>; */

tx-pin = <18>; /* <&interface_to_nrf52840 1 0>; */

cts-pin = <19>; /* <&interface_to_nrf52840 2 0>; */

rts-pin = <21>; /* <&interface_to_nrf52840 3 0>; */

};

9160 (main.c)

Device binding is to UART_1:

struct device *uart = device_get_binding("UART_1");

52840 (main.c)

nrf_libuarte_async_config_t nrf_libuarte_async_config = {
        .tx_pin = 17,
        .rx_pin = 20,
        .baudrate = NRF_UARTE_BAUDRATE_115200,
        .parity = NRF_UARTE_PARITY_EXCLUDED,
        .hwfc = NRF_UARTE_HWFC_DISABLED,
        .timeout_us = 100,
        .int_prio = APP_IRQ_PRIORITY_LOW};

Question:

I can get all of this to work (or appears to) when I;
* start the 9160
* move sw to nRF52
* build->debug from SES
 -> click the green run button

* This appears to do everything correctly, receives ANT+, transmits from 52840 to 9160 and I can see it display on the 9160 tty port (using screen).

If I do it any other way, its as if the code on the 52840 is not running, or there is a problem with the connection or a timing issue ?

I added a nrf_delay_ms(5000) at the start of the 52840 code, just in case there was a timing issue between the 9160 and 52840 in that the UART was not ready - but that didnt work.

What am I missing here ?
I feel I have done every possible combination of switches, power and reset, but the only way I can get it to work is if I use SES Build->Debug 

thanks in advance

-brett

[Vidar Berg]

Hi Brett,

On the 52840 side, could you try to call sd_clock_hfclk_request() after enabling the Softdevice? This will make the Softdevice keep the HF crystal oscillator (HFXO) on and in turn increase the accuracy of the UART baudrate generator (it runs off the less accurate HFINT clock by default). I think it's worth trying since you seem to get more stable performance when you keep the chip in debug mode.

I will try to see if I can replicate it here if the above doesn't help.

Best regards,

Vidar

[Brett]

Hi Vidar,

No difference.  It still works in debug mode but fails otherwise.

-brett

[Brett]

Hi Vidar,

For now I am only trying to send data from the 52840 to the 9160 - so the flow-control should not be an issue ?

I have attached the code that I have, if you are able to try this on your board to see if it works for you, and/or if there is something obvious I have missed.

Note; This code is a cut/paste from one of the BLE examples which I have not completely cleaned up yet.
This code has also been cut down to send `1` every 5 seconds over the UART connection, so your 9160 receiver should be able to get the message and log it.

cheers

-brett

app_libUARTE.tar.gz

[Vidar Berg]

Hi Brett,

I have to spend some more time on this, unfortunately. I realized that my UART implementation on the 9160 isn't working properly either when I started testing with your example. Will try to get you an update tomorrow.

Cheers,

Vidar

[Brett]

Thanks Vidar, appreciate you having  a look at it for me.

I can send over my 9160 code as well if that helps at all.

[Vidar Berg]

Hi Brett,

I have hopefully figured it out now: in your project you used printf's to print the debug message over RTT, which unlike the NRF_LOG_* macros, are blocking. That is, printf() won't return until the debug message has been received by the debugger.

I think this must be the reason why it only worked when you did SES Build->Debug in the beginning. Please try to use the NRF_LOG_*  macros instead to confirm.

I also made some changes to my 9160 project in the process. Here is my updated version:

3757.uart_52840_9160.zip

[Brett]

Hi Vidar,

Thanks !  That was the answer, printf() was blocking - all appears to be working now.

Trap for new players !

regards

-brett

[Vidar Berg]

Hi Brett,

I'm glad to hear that it works, thank you for the update. This isn't just a trap for new players - I was not aware of it either I have never used printf's with RTT though, only UART.

Cheers

Vidar