nRF9160 AT client UART0 pins reassignment issue

RE: nRF9160 AT client UART0 pins reassignment issue

Simon — Wed, 15 Jul 2020 18:39:54 GMT

Could you try to configure the UART according to External MCU configuration?

It says that flow control should be used, so you could try to either add RTS and CTS in your custom board folder or through an overlay file.

You could test it with an nRF52 DK first, to make sure it's working, then swap it with your external MCU.

Best regards,

Simon

RE: nRF9160 AT client UART0 pins reassignment issue

Smart.Enrg — Tue, 14 Jul 2020 06:42:45 GMT

Hi Simon,

Following Erase All in nRF connect/ programmer - do I need to flash modem f/w, before flashing my app (SLM or AT client) hex?

Best,
SE

RE: nRF9160 AT client UART0 pins reassignment issue

Smart.Enrg — Tue, 14 Jul 2020 01:57:54 GMT

Here are some more inputs -- I think this might explain how failing (stopped) RX could hold back TX (missing response to AT command). Not sure what's the root cause of these warnings emanating from uart_callback()

Guess the question is - what might cause this to happen, what's different in my (custom .dts) case compared to DK/ profile?

Please advise.

RE: nRF9160 AT client UART0 pins reassignment issue

Smart.Enrg — Sun, 12 Jul 2020 15:44:12 GMT

Thanks Simon,

The Tx, Rx pin settings reflected in various config/ build files that you pointed to - they all seem to check out ok in my case.
Still no luck sending data; so couple of follow-up questions:
1) When I try this same SLM app on nRF9160-DK (v0.9.0), built with its own (nrf9160dk_nrf9160_common.dts) profile.
It works well. Though what I noticed, there I need to select COM15 in Link Monitor (VCOM14,15,16 associated with this
DK). Is VCOM15 associated with/ mapped to UART0 or UART1 on nRF9160-SiP? BTW my prj.conf for this build too, is
calling for UART0. Also, what does "CONFIG_UART_0_NRF_HW_ASYNC_TIMER=2" (i.e. Async and Timer=2) mean?
2) UART0 in nrf9160dk_nrf9160_common.dts specify RTS, CTS, which I don't use in my custom profile (.dts). Could that
mean original SLM app (DK build) is calling for/ require handshaking? which I'm not using - that will explain unable to
send too.

Tried your suggestion about setting breakpoints inside uart_rx_handler() from slm_at_host.c. One breakpoint set right after entering rx handler and another right after "send:" label. None of the break points are hit when I send a simple AT\r\n. So, I
am trying to trace where it's lost? I can see/ by probing P0.09 of nRF9160-SiP from an external USB serial connection that
correct command stream does hit rx-pin (P0.09) = 0x41 0x54 0x0D 0x0A. Now the only things left to suspect is TX signal level (2.6V) that's connected to rx-pin (P0.09) - it should be valid (VIH) level for proper rx-pin detection, but please confirm
that for me. As mentioned the external processor I am using to interface with nRF9160-SiP - IO levels on that are 2.7v nominal. I do have a level shifter on nRF91 tx-pin so as to not violate 2.7V rx input on the external processor host.

Please advise. Thanks again.

Best,
SE

RE: nRF9160 AT client UART0 pins reassignment issue

Simon — Sat, 11 Jul 2020 19:30:19 GMT

[quote user="SmartEnrg"]Am I supposed to modify any other file (other than the .dts attached)? I read somewhere about overlay file -
what does that do?[/quote]

The overlay file can be used to overwrite the fields of the DTS nodes in the board folder (e.g. the rx and tx pins of uart0). However, it shouldn't be necessary in your case, since the tx and rx pin are set to the desired values.

[quote user="SmartEnrg"]Also, for config changes - am I supposed to change prj.conf or menuconfig/ defconfig?[/quote]

Since you're using uart0, make sure CONFIG_SLM_CONNECT_UART_0=y and CONFIG_SLM_CONNECT_UART_2=n, you can confirm that the configurations are set correctly by checking the file ncs\v1.3.0\nrf\applications\serial_lte_modem\build\zephyr\include\generated\autoconf.h (you have to build your application first).

[quote user="SmartEnrg"]Another observation, - I see nrf9160dk_nrf9160ns.overlay in \ncs\v1.3.0\nrf\applications\serial_lte_modem
but I don't see one for my custom board profile. Should there be one?[/quote]

I looked inside the file ncs\v1.3.0\nrf\applications\serial_lte_modem\nrf9160dk_nrf9160ns.overlay and saw that it only configured uart2. You are using uart0, and it is already configured in the file nrf9160_nRFstamp91_common_dts.txt, so I don't think you need to add an overlay file for your board.

One way to check if the fields for uart0 is set correctly is to look inside the file ncs\v1.3.0\nrf\applications\serial_lte_modem\build\zephyr\include\generated\devicetree_unfixed.h. Check if DT_N_S_soc_S_peripheral_40000000_S_uart_8000_P_tx_pin (I think that is the correct name) is equal to 8.

A cleaner approach is to run printk("TX pin: %d\n"DT_PROP(DT_NODELABEL(uart0), tx_pin)) in ncs\v1.3.0\nrf\applications\serial_lte_modem/src/main.c-->main().

Could you check one thing? The application slm_at_host.c won't send data (use tx pin), until it has received (use rx pin) a complete AT command in uart_rx_handler(), submitted a work queue item which triggers cmd_send(), sent it to the modem, received a response from the modem. Then it will send the response (use the tx pin).

Could you set a breakpoint or add some logging at the bottom of static void uart_rx_handler(..):

tatic void uart_rx_handler(u8_t character)
{
    .
    .
    .
send:
    //Check if it goes here
	uart_rx_disable(uart_dev);
	k_work_submit(&cmd_send_work);
	at_buf_len = cmd_len;
	cmd_len = 0;
}

You could also do some debugging in cmd_send() and check if rsp_send() runs.

Best regards,

Simon

RE: nRF9160 AT client UART0 pins reassignment issue

Smart.Enrg — Fri, 10 Jul 2020 04:21:55 GMT

Thanks Simon,

Please see .dts and prj,conf attached - had to change file extensions to get rid of file upload errors here to this
ticket. Also note my software setup details and key pin measurements:

Software/ Firmware version/ settings:
* modem f/w v1.2.0 - programmed first (after erase all) using nRF Connect desktop (v3.4.1)/ Programmer (v1.4.3)
* after modem f/w - next I flash Erase/ Write serial_link_modem from nrf connect sdk (ncs) v1.3.0. This hex built
using SES and custom dts (attached).

Key pin measurements:
* VDD 3.3V
* Reset pin (driven from external processor) 2.7V

The problem I'm facing, despite correct (uart0) settings in .config - nRF9160 doesn't seem to drive tx-pin (8).
Am I supposed to modify any other file (other than the .dts attached)? I read somewhere about overlay file -
what does that do? Also, for config changes - am I supposed to change prj.conf or menuconfig/ defconfig?

Another observation, - I see nrf9160dk_nrf9160ns.overlay in \ncs\v1.3.0\nrf\applications\serial_lte_modem
but I don't see one for my custom board profile. Should there be one?

devzone.nordicsemi.com/.../prj_5F00_conf.txt devzone.nordicsemi.com/.../nrf9160_5F00_nRFstamp91_5F00_common_5F00_dts.txt

Best,
SE

RE: nRF9160 AT client UART0 pins reassignment issue

Simon — Wed, 08 Jul 2020 22:38:47 GMT

Could you upload your sample or a simplified version of it? Then I'll test it myself and see if there is something wrong with the DTS files or the configuration.

Best regards,

Simon