I am using NUS, is it really necessary to use WDT?

[pkr2258]

hi

We are developing Central and Peripheral Devices based on the NUS example.

What I would like to inquire about is

The NUS example does not include WDT by default, but WDT is usually essential when developing MCU...

Is it necessary to use WDT in NUS-based product development?

thank.

[Karl Ylvisaker]

Hello,

The NUS example does not include WDT by default, but WDT is usually essential when developing MCU...

Is it necessary to use WDT in NUS-based product development?

The sample does indeed not include WDT, since this is not the functionality that it demonstrates.
The samples in the SDK is not meant as deployment-ready applications, and while we recommend that you use the samples as the foundation for your application development we also urge you to modify them to more closely align with your project or the use-case you are targeting.

The sample is also very simple, and so you might want to add more than just the WDT functionality before you deploy it to products in the field (unless of course the sample completely matches all your requirements already, which is possible but perhaps unlikely). Could you tell me more about the use-case you are targeting, and the requirements and constraints of your application?

Best regards,
Karl

[pkr2258]

hi

I am developing a BLE controller and BLE module.

As I mentioned, it is NUS-based, the remote control is being developed as Peripheral, ​​the transmitting/receiving module is being developed as Central, and the implementation of basic functions has been completed.

Like the basic operation of NUS, it operates in a structure that continues to check the status while exchanging dummy data while the BLE remote control and BLE transmitting/receiving module are connected.

So far, there have been no problems even without using WDT...

I don't know what kind of problems might arise in the actual field... I'm thinking about WDT.

[Karl Ylvisaker]

Hello,

pkr2258 said:

I don't know what kind of problems might arise in the actual field... I'm thinking about WDT.

It is very hard to say what kind of problems that could occur in the actual field since I do not know what changes you will be making to the application, or what kind of environment it will be operating in, but if you are running the unmodified example it should run smoothly by itself for the most part.

Some issues you potentially could run into then is unexpected disconnections, buffer overflows, or unexpected UART transmissions, but at least I do not think there are any race conditions in the standard application, and so all of these errors could perhaps be handled either with specific error handling, or just to reboot the device - if this would be feasible for your applications usage.

Best regards,
Karl

[pkr2258]

hello,

As you said, even without WDT based on NUS, no abnormal symptoms have occurred yet.

However, in the case of Central receiving DC power from another PCB,

If the DC power fluctuated greatly (determined to be an abnormal operation of the LDO), it did not operate normally.

There were cases where GPIOs were in high impedance and J-Link was also not connected.

In the case of abnormal voltage, I thought it would be solved with BOR, but it wasn't, so I'm considering WDT.

[Karl Ylvisaker]

Hello,

pkr2258 said:

In the case of abnormal voltage, I thought it would be solved with BOR

This will depend on the characteristics of the 'abnormality', i.e how the voltage is behaving differently from what you would have expected.

pkr2258 said:

I'm considering WDT.

From my limited visibility into your project it sounds like it could be a good idea to add the WDT, as a fallback in case anything unexpected happens in the environment around the nrf.

Please do not hesitate to open another ticket if you should encounter any issues or questions with your work to add the WDT to your project! :)

Best regards,
Karl