Zephyr, NRFConnect 2.3, and BLE reading/writing

[scath]

Can someone please, for the love of all that is holy, point me towards some guidance on how to read values of custom characteristics set by another device?

I cannot find this ANYWHERE.

[Amanda Hsieh]

Hi, 

Hope this  nRF Connect SDK Bluetooth Low Energy tutorial part 1: Custom Service in Peripheral role and this https://academy.nordicsemi.com/topic/blefund-lesson-4-exercise-1/ can help you. 

Regards,
Amanda H. 

[scath]

Hi Amanda,

I'm sorry to say this really doesn't help. 

Again, I'm trying to read characteristics belonging to a service setup and advertised by another device. Since it's my device, my service, and my characteristics I know all the UUIDs.

What I'm not seeing is a way to read these characteristics. 

Please bear in mind, I don't want to read them on my mobile phone - I want to read them from another device.

Are you able to point me to the appropriate sections of those pages, or direct me to a more appropriate resource.

Thanks,
S.

[Amanda Hsieh]

Hi, 

You can use bt_gatt_read(). See this example which is used by https://github.com/nrfconnect/sdk-nrf/tree/b108f364ccf11f52248decabb26cb22ffd30f039/samples/bluetooth/central_bas

-Amanda H. 

[scath]

Hi Amanda,

Thank you - This is closer. With this example code in hand I've been able to set up a framework that reads some characteristic values

However, the example you sent revolves around a single characteristic. I have multiple characteristics in the service: some need to be read from, some need to be written to, some need a subscription.

The guidance I'm primarily looking for is on how to set up each unique characteristic for our intended use - this is what I'm not able to find.

Sadly, all of the example code I seem to find is extremely poorly documented. Huge leaps of logic, dependencies on standard/pre-established devices/services, and unclear flow of execution; this is making setting up characteristics very difficult.

Can you point me to guidance on this?

Thanks again,
S.

[Amanda Hsieh]

Hi,

scath said:

I have multiple characteristics in the service: some need to be read from, some need to be written to, some need a subscription.

Then, this https://github.com/nrfconnect/sdk-nrf/blob/750b0d51e152534fe274ba66c7cf29b22c45c34a/subsys/bluetooth/services/hrs_client.c would be suitable for your usages which show how to read, write and subscribe characteristics in the Heart Rate Service. 

You can take a look at the Generic Attribute Profile (GATT) documentation. 

-Amanda H.

[scath]

Thanks for the speedy reply, Amanda. I'll take a look asap!

Cheers!

[scath]

Hi Amanda,

I appreciate the effort, and I've been able to work out some of what's happening here, but I have to say that the documentation is absolutely awful.

Having reviewed the code you suggested, I find exactly 4 short comments across several hundred lines of code. It vaguely lays out a strategy for setting up the BLE framework, but has no guidance on actually implementing the code.

For example: Lines 185:218 of `hrs_client.c` define `bt_hrs_client_measurement_subscribe()`... but there's no demonstration or discussion on where this actually gets called. That's confusing, since this method requires a custom callback as an argument. It would be very helpful to see where that method gets called, and the custom callback declared and set up for actual execution.

Can I ask you for some guidance on setting this up, and/or where I can find discussion on the intended execution path for the multithreaded BLE system? Though I admittedly may not have seen it, I'm not finding information on this.

Many thanks,

S.