Zephyr UART on nRF5340 hardware flow control tx breaks

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

Susheel Nuguru — Mon, 15 May 2023 11:47:58 GMT

Radoslaw, Could this be related to this issue? The fix for this is supposed to get into our next NCSv2.4.0

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

Susheel Nuguru — Thu, 11 May 2023 09:10:29 GMT

I will have to start an internal investigation for this as I am not able to reproduce this issue. I will have to also see if anyone internally have used this configuration in any other setups.

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

AstralStorm — Mon, 08 May 2023 16:50:20 GMT

The firmware was already up to date according to J-Link Configurator v7.88a. Version: 2022 Nov 7 16:22.

JLink x64 7.84a to 7.88a update sadly changed nothing either. (The 32-bit one is kept at 7.60a for NCS Programmer compatibility.)

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

Susheel Nuguru — Mon, 08 May 2023 11:46:48 GMT

We have noted that HWFC have some issues with some JLink versions. Can you please check if you have the latest JLink drivers?

After you install the latest JLink, you need to open Segger J-Link configurator and update the firmware on the nRF DK.

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

AstralStorm — Fri, 05 May 2023 12:58:04 GMT

How can I turn off dynamic flow control for the VCOM? Seems not possible.

Other than that, RealTerm opens the port with RTS set and DTR set, I can change either to Clear, otherwise responds as expected (at least as expected by nRF9160).
Should it be DTR set and RTS clear?

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

Susheel Nuguru — Fri, 05 May 2023 12:53:22 GMT

Can you try not using dynamic flow control and also make sure that the pins initial state for CTS and RTS are as expected before the transaction starts on the pins.
Seems like something is off with initial state of the hwfc pins.

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

AstralStorm — Thu, 04 May 2023 10:49:44 GMT

Interestingly enough going via direct pins (and correctly configured UART1) mostly works - every third command is not sent, so the main issue is somehow limited to VCOM. Could dynamic HWFC be the cause?

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

AstralStorm — Thu, 04 May 2023 09:15:59 GMT

I'm a bit confused about this statement, since pincontrol for uart0 is the following by default
(from zephyr\boards\arm\nrf5340dk_nrf5340\nrf5340_cpuapp_common-pinctrl.dtsi)
thus enables the pull-up on RX and CTS, and I'm using VCOM to talk to a PC via USB.

    uart0_default: uart0_default {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 20)>,
                <NRF_PSEL(UART_RTS, 0, 19)>;
        };
        group2 {
            psels = <NRF_PSEL(UART_RX, 0, 22)>,
                <NRF_PSEL(UART_CTS, 0, 21)>;
            bias-pull-up;
        };
    };

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

Susheel Nuguru — Thu, 04 May 2023 09:01:19 GMT

Looking at your configuration in the project that you shared.

And not knowing the default pull configuration of the peer that is communicating with this, I would suggest you to have both CTS and RTS pull up enabled. I also suggest you to find out the pin pull configuration of the peer device's CTS and RTS that is talking to this uart module.

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

AstralStorm — Wed, 03 May 2023 09:22:09 GMT

The project should not particularly require a path, you might need to remove the .vscode directory if you're using visual studio for the import. That bit could have a hardcoded path. Otherwise, all the paths are relative in CMake files.
Import to nRF Connect SDK in Visual Studio code with "main" as the project should build fine either as nrf5340dk_nrf5340_cpuapp or cpuapp_ns board, or just running from top dir:
west update
west zephyr-export
west build -b nrf5340dk_nrf5340_cpuapp -s main -d main/build -p
west flash -d main/build

as long as zephyr environment variables are set. It has come to my attention that cpuapp_ns device tree has a commenting typo error which you should be able to easily fix.

nRF9160 side works when interacted with the terminal from the PC side, which is why it's not an issue with that. (It uses the default settings from SLM application.) The nRF53 side does not send to PC via VCOM.
RTS/CTS settings for pullup are the default.

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

AstralStorm — Wed, 03 May 2023 08:44:00 GMT

The project should not particularly require a path, you might need to remove the .vscode directory if you're using visual studio for the import. That bit could have a hardcoded path. Otherwise, all the paths are relative in CMake files.
Import to nRF Connect SDK in Visual Studio code with "main" as the project should build fine either as nrf5340dk_nrf5340_cpuapp or cpuapp_ns board, or just running from top dir:
west update
west build -b nrf5340dk_nrf5340_cpuapp_ns -s main -d main/build
west flash -d main/build

as long as zephyr environment variables are set.

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

Susheel Nuguru — Tue, 02 May 2023 19:00:01 GMT

Hi Radoslaw,

Sorry for delays, Maria is not feeling well and I will try to assist you.

[quote user=""]The lockup (waiting on flow control I think) happens on first send.
HWFC disabled sends correctly, receives most of the things, but due to lack of flow control it loses data on receive, so I cannot use it.[/quote]

I thought that this is a nRF53 case but looking at the sources this looks like nRF9160.

When you are able to send when the flow control is disabled, then rest of the code on your device is functioning correctly regarding UART configuration. As soon as you enable the flow control, you are not able to send means that the CTS pin configured in your UART configuration is never getting a green light. This could be because of wrong Pull configuration of CTS. Can you check the CTS pull configuration you are using? I tried to compile your project but it looks like it needs to be in a specific path. I want to see your device tree settings for uart and its pins pull configuration.

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

Maria Gilje — Mon, 24 Apr 2023 12:27:03 GMT

Hello,

Thank you for the test code. I will get back to you shortly.

Best regards,

Maria

RE: Zephyr UART on nRF5340 hardware flow control tx breaks

AstralStorm — Fri, 21 Apr 2023 12:21:46 GMT

Attaching the test code, based on gsm-ppp.
Normally built with debugging options on and cpuapp (secure) only as that makes debugging a slight bit easier.
devzone.nordicsemi.com/.../RS_2D00_nRF_2D00_serial_2D00_test.7z

(Oh, also, VCOM flow control switches on the nrf5340 DK v2.0.0 are in the ON position. Solder bridges were not reconfigured.)