how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Mon, 01 Nov 2021 09:46:46 GMT

This ticket shall be closed, As I can interface with external GPIO and able to wakeup UART from sleep

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

ovrebekk — Tue, 28 Sep 2021 13:23:55 GMT

Hi Ilanchezhian

Håkon is currently out of office, and I will assist in the mean time.

[quote user="Ilanchezhian T"]I am confused what is COM8 in your case , is it the one of the enumerated port of Jlink ?.[/quote]

This should be one of the three comports enumerated by the nRF9160DK, yes. I will confirm this when he is available.

[quote user="Ilanchezhian T"]But Anyway , If I am using it has the external host interface where instead of using the UART0 ,using UART2 I could able to successfully sleep using AT#XSLEEP=2 command and wakeup using the port pin P0.31. This works with both Debug as well as run mode. [/quote]

If I understand you correctly you can not get it to work if you try to use UART0 with default settings, but it works if you use UART2 and route the pins from the nRF9160DK to the external uart-ttl-usb device?

Or are you using your own custom hardware rather than the DK?

COM45, 46, 47 in your case should be connected to the nRF9160 on the DK, and would not be connected to the nRF9160 on your own board.

Best regards
Torbjørn

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Fri, 24 Sep 2021 14:46:19 GMT

Hi Helsing,

Thanks for your reply.

Thanks for confirming that for me LTE link monitor stopped sending anything after issuing sleep AT command and pressing the wake up button.

I am confused what is COM8 in your case , is it the one of the enumerated port of Jlink ?.

If that is the case in my case it is as COM45, 46, 47 , I tried in all ports but it is not working , it is not able to read the Ready message which used to appear when the modem gets powered ON.

But Anyway , If I am using it has the external host interface where instead of using the UART0 ,using UART2 I could able to successfully sleep using AT#XSLEEP=2 command and wakeup using the port pin P0.31. This works with both Debug as well as run mode.

Right now our use case is to have MCU to have external uart communication, But you can still suggest if I do need to test.

With Regards

Ilanchezhian T

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Fri, 24 Sep 2021 13:09:11 GMT

Hi again,

It looks like I have been able to reproduce this, and we might have a workaround.

[quote user="Ilanchezhian T"]BUT IF I REMOVE the breakpoints and do the same it is not working as expected , in fact nothing happens, what is that i am doing wrong. [/quote]

Exactly what is not working? Is the board not waking up? Are you able to send more AT commands? If you are not able to send anything it could be that LTE Link Monitor is failing.

I have been able to reproduce similar behavior where LTE Link Monitor stops working after the breakpoints are removed.

Could you please try debugging the board without LTE Link Monitor and switch to a dedicated serial output terminal? Here are the settings that worked on my side. Please note that you might need to select a different COM-port on your side. I have flow control enabled as I am using SLM out of the box.

Below shows the use of AT#XSLEEP=2 and wake up by button.

Please let me know if this works on your side. Is this a satisfying workaround at this stage? The issue you reported is is possibly a corner case related to LTE Link Monitory. Hopefully, you should be able to used LTE Link Monitor going forward with your project.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Thu, 23 Sep 2021 14:09:14 GMT

Hi Ilan,

Have you made any modifications to SLM? Have you enabled any configs or implemented the changes related to disabling flow control?

I am not seeing this when I am testing SLM myself. I tested without any breakpoints, and when I press the button, I can see 'Ready' appear in LTE Link Monitor:

Would you be able to share your project files?

Best regards,

Håkon

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Wed, 22 Sep 2021 15:25:04 GMT

Hi Helsing, I am trying to put UART in sleep mode using AT#XSLEEP=2. I could see that If I put breakpoint uart power on and uart powerOFF function of SLM sample application this features works and if I remove the breakpoint is not working.

My Observation:

UART 0 is enabled and UART2 is disabled

Breakpoint is placed at uart power on() and uart power off() function

provide the command AT#XSLEEP=2, break point hit in uart power off () function , run the progam

Pressed Button 0 in the nrf9160 board , break point hit on the uart power on () function , run the program

provide Any uart command it works

BUT IF I REMOVE the breakpoints and do the same it is not working as expected , in fact nothing happens, what is that i am doing wrong.

Please find the Link monitor terminal logs and screen shots attached for further investigation. devzone.nordicsemi.com/.../log_5F00_sleep_5F00_test2_5F00_forum_5F00_post.txt

Thanks

Ilan

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Mon, 30 Aug 2021 12:38:21 GMT

1. Assume that the modem and application on nRF9160 normally takes responsibility for sleeping whenever there is nothing to do.

2. Please refer to Power saving #XSLEEP. #XSLEEP has three options, so the host may put nRF9160 to idle, sleep, or only put the UART to sleep.

When the host MCU wants to wake up the UART, use the GPIO.
When the host MCU wants to turn off the UART, send AT#XSLEEP=2 to put the UART only to sleep.

The UART consumes around 700µA so it should be put to sleep whenever possible. After eDRX/PSM is requested, it is important to verify that this is accepted by the network. XMODEMSLEEP is useful for synchronizing sleep and wake-ups when optimizing power consumption.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Fri, 27 Aug 2021 14:15:15 GMT

Yes, you need to delete hw-flow-control; under &uart2 in the nrf9160dk_nrf9160ns.overlay file.

&uart2 {
	compatible = "nordic,nrf-uarte";
	current-speed = <115200>;
	status = "okay";
	tx-pin = <10>;
	rx-pin = <11>;
	rts-pin = <12>;
	cts-pin = <13>;
	//hw-flow-control;
};

You can verify that hw-flow-control is completely gone from uart2 by checking the device tree in your build folder, build/zephyr/zephyr.dts.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Thu, 26 Aug 2021 10:25:38 GMT

I am still to explore on this GPIO. But have few queries regarding this

1. How does the MCU host gets indicated that nRF9160 is in idle or sleep state.

2. When do we need to activate this GPIO to save power, For example my use case is that let's say during host powered ON , it sends set of AT commands initially to connect to network with say eDRX and PSM mode enabled/disabled. And then host application is sending the data to the external devices every 5 mins once.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Thu, 26 Aug 2021 10:18:24 GMT

Hi Helsing, I could get my application running with 3 wires and able to communicate with external uart ttl 3V3 cable. The change made is that removed RTS,CTS and hW-flow-control configurations in the nrf9160dk_nrf9160ns.overlay file . Then I just compiled the same and tested it got worked

Thanks for your support.

Ilanchezhian T

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Thu, 26 Aug 2021 10:08:33 GMT

Thanks for the clarification on this

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Wed, 25 Aug 2021 14:36:10 GMT

2.a) Using the GPIO is the recommended way to go. If saving one pin is important, you may leave the peripheral running while the application is sleeping. This would add an extra ~0.5 mA.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Wed, 25 Aug 2021 13:58:38 GMT

[quote user="Ilanchezhian T"]2) What are the necessary UART pins required ( As per the application note we have seen that 5 pins (RTS,CTS,RX,TX,GPIO) are mentioned,
I think GND pin is also required as the uart signals are not differential signals)[/quote]

2) Normally, only the three connections RX, TX and ground are needed for UART to work without flow control. I have not yet been able to confirm whether someone has tested disabling this with serial_lte_modem, specifically.

[quote user="Ilanchezhian T"]2.a) If all the pins are not required ( then RX,TX,GND) is ok to establish connection between modem and our host microcontroller[/quote]

2.a) The serial_lte_modem has a config option, CONFIG_SLM_INTERFACE_PIN - Interface GPIO to wake up or exit idle mode, for setting up an additional GPIO between nRF9160 and the external MCU. This GPIO seems to be used for exiting nRF9160 from IDLE or sleep. If you have another way to wake up nRF9160, then only RX, TX and GND are needed between the two devices.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Wed, 25 Aug 2021 10:10:24 GMT

6.a) Thank you for the clarification. In order to program the nRF9160 SiP you only need the programming interface mentioned as a reply to 6).

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Wed, 25 Aug 2021 07:16:11 GMT

6.a) Question is - Do we need to have similar hardware circuitry as present in nRF9160 DK ( usb connector and debugger circuitry) in our product in order to code flashing in both Modem Processor and Application Processor.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Wed, 25 Aug 2021 07:02:10 GMT

[quote user="Ilanchezhian T"]5) We might need to develop the custom hardware that gets plugged into our product, How easy is to customize the "LTE Serial Modem" software available as part of nrf9160 SDK[/quote]

It sounds like changing a few configs and device tree properties will allow you to run the application on a custom board. We are not testing the applications in all possible combinations of configurations, so you would need to perform tests, like any project.

[quote user="Ilanchezhian T"]5.a) If it is very simple only in terms of configurations please provide us some steps to perform this[/quote]

This should be feasible. Going through the application description and the section on Connecting with an external MCU should get you started. I will be back with more details.

One approach, as you are moving forward, might be to demonstrate the setup using an nRF 52 series DK. This setup has been tested, and it allows you to get familiar with the functionality.

Please also read the section Extending the application.

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Tue, 24 Aug 2021 21:07:47 GMT

[quote user="Ilanchezhian T"]4) Our microcontroller I/O line is 3.3V does the nRF9160 supports 3.3V on its I/O line[/quote]

4) Yes. As mentioned above, make sure to configure nRF9160 accordingly.

[quote user="Ilanchezhian T"]6) In our custom hardware , to flash the nrf9160 modem software and its MCU for applications, What are the additional circuitry required other than the uart I/F connections, VCC and GND ?[/quote]

6) You will need the 10-pin programming interface in Table 1. Does your board have tight pcb area constraints? If that case, you could convert this to a 6-pin interface. The board will in any case need to have it's own supply as this is not supplied through the programming interface.

[quote user="Ilanchezhian T"]6.a) I think we need usb and jlink circuitry, please provide your input in this regard[/quote]

6.a) Sorry, I am not sure exactly what you are asking for. Could you please explain?

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Tue, 24 Aug 2021 14:25:27 GMT

1.a) This approach should be fine. Just make sure the voltages are correct. It could be a good idea to measure the voltages from the USB-232-3V3 cable to see if they infact are 3V3. Have you checked this communication with a scope? Also remember to set up nRF9160 DK for 3V3 communication. You can set the VDD voltage to 3V0 with SW9, however, you probably need to go to 3V3. This can be done by customizing the DK's voltage level. If you apply 3V3 to VIO_REF(P20) then the GPIO voltages should be adjusted automatically.

[quote user="Ilanchezhian T"]3) What are pins present in nRF9160-DK can be used to have external UART interface with host microcontroller[/quote]

3) You may choose any pin that is not already in use. I could get back to you with a few examples.

Answers to the rest of your questions will follow later today.

Best regards,

Håkon

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Mon, 23 Aug 2021 10:11:42 GMT

Hi ,

Let me put down what I am trying to Evaluate.

Our objective is to use the nrF9160 as a module which can act as AT modem and can be
interfaced with our 16bit microcontroller via UART I/F.

Setup for Evaluation:

Hardware used - nRF9160-DK

Software used -

1. Modem Firmware - mfw_nrf9160_1.3.0

2. SDK - version 1.6.1

3. Application Software - LTE Serial Modem ( present in the installed sdk under location : C:\ESLI\nrfIDE\v1.6.1\nrf\applications\serial_lte_modem)
- Please suggest is this a right application we have choosen for our use case

4. With the USB cable connected and emulated via VCOM port, we are able to communicate via NRF link Manager software using AT commands

Queries:

Please note as we do not know how the "LTE Serial Modem" software is written we have certain queries which are listed below,
also for initial evaluation we are planning to use the nrF9160-DK, before going with custom hardware

1) For our initial validation to check external UART is possible, I am planning to connect the pins of USB-232-3V3 cable
to the UART pins present in the nrF9160-DK and provide AT command via any PC serial terminal software like Docklite for example.
1.a) Could you please let us know this appoach is fine. This is what we are trying and could not do as of now.

2) What are the necessary UART pins required ( As per the application note we have seen that 5 pins (RTS,CTS,RX,TX,GPIO) are mentioned,
I think GND pin is also required as the uart signals are not differential signals)
2.a) If all the pins are not required ( then RX,TX,GND) is ok to establish connection between modem and our host microcontroller

3) What are pins present in nRF9160-DK can be used to have external UART interface with host microcontroller
3.a) Does any modifications in "LTE Serial Modem" software [OR] some configuration that needs to be done to have "LTE Serial Modem" with respect to UART interface

4) Our microcontroller I/O line is 3.3V does the nRF9160 supports 3.3V on its I/O line

5) We might need to develop the custom hardware that gets plugged into our product, How easy is to customize the "LTE Serial Modem" software available as part of nrf9160 SDK
5.a) If it is very simple only in terms of configurations please provide us some steps to perform this

6) In our custom hardware , to flash the nrf9160 modem software and its MCU for applications, What are the additional circuitry required other than the uart I/F connections, VCC and GND ?
6.a) I think we need usb and jlink circuitry, please provide your input in this regard

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Wed, 18 Aug 2021 14:10:10 GMT

Thanks for the response.

1. I could see the different information ( mentioned in nRF9160 DK HW manual and application description in developer guide) regarding the UART2 pins of the nrF9160. Which one is correct I am really confused.

2.regarding the settings to be touched I have taken a screen shot, could you provide your feedback for the same.

3. As I am new to embedded linux based development, I do not really understand how feature configuration and pin configuration works in the form of .dts, .dtsoverlay, menuconfig and prj.conf. Please let me know the proper steps to configure and use application processors UART2 of nRF9160 in 2 pin mode. My end objective is to interface my external MCU host via UART interface to communicate via UART I/F with nrF9160 modem via AT commands.

Thanks

Ilanchezhian T

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

helsing — Wed, 18 Aug 2021 09:18:18 GMT

Take a look at this case and let me know how it goes.

Disable HWFC in serial modem application

Best regards,

Håkon

RE: how to interface external MCU host viaUART interface with nrf9160, with only 3 pins from UART (RD,TX,GND)

Ilanchezhian T — Mon, 16 Aug 2021 03:56:29 GMT

Before connecting any other host MCU, is there a way to connect the external USB to UART TTL cable to test the function of modem nrf9160 using AT commands.

If so please let me know the steps to do that in nRF9160 development kit https://www.nordicsemi.com/Products/Development-hardware/nrf9160-dk

With Regards

Ilanchezhian