BlueFruit52: indications?

[jevada]

I am writing a Cycling Power service on an nRF52 Feather that requires a response when writing to its control point. If I understand the spec (see here) correctly, this respons basically is an indication with a response in its payload. How do I send an indication from the bluefruit library?

(Hmm... perhaps this is not the right subforum to post this question. Please move if appropriate).

[bigwheels]

I have the Bluefruit nRF52 set up as a peripheral where I write to the peripheral from my central. I've not read any values from the nRF52, but I believe the code/commands you'll need can be found here:

API reference: https://learn.adafruit.com/bluefruit-nr ... acteristic
HRM example: https://github.com/adafruit/Adafruit_nR ... om_hrm.ino

If your central is expecting to read the value of a characteristic broadcast by the nRF52, I'd imagine you'd set the following property for your characteristic, BLECharacteristic.setProperties(CHR_PROPS_READ) and then trigger the broadcast using BLECharacteristic.read().

Or if your central is expecting to be notified of updated values, use BLECharacteristic.setProperties(CHR_PROPS_NOTIFY), and BLECharacteristic.notify()

I don't know the full code and exact syntax as I haven't done this, but the resources above should allow you to figure it out.

[jevada]

Thanks mate, I am aware of those pages. They do not provide information on indications.

An indication basically is a notification, but than with expecting an acknowledgement from the central. The CHR_PROPS_INDICATE attribute is known in the API, but in contrary to a BLECharacteristic::notify() method, there seems to be no BLECharacteristic::indicate() or something like that.

A control point (if I read the spec correctly) basically is a write/indicate pair. The control point can be used to execute a command on the peripheral that responds through an indication once it has excecuted the mentioned command.

For example, looking at the Cycling Power Control Point (spec here) there's an opcode 0x15 meaning "Request Factory Calibration Date". The explanation reads: "The response to this control point is Op Code 0x20 followed by the appropriate Response Value, including the value of the Factory calibration date in the Response Parameter.".

So the central writes to the control point with opcode "0x15", after which the peripheral responds by sending an indication "0x20" followed by the value of the requested calibration date. For this, we need indications, not notifications.

[bigwheels]

yep - you're right. Indicate needed, but looks like no Indicate() in the Bluefruit library. I wonder if the adafruit guys haven't gotten to that yet, as the nRF52 is new and evolving. Check with Nordic?

[hathach]

hi there,

thank you for asking the question, so far we haven't working on any service that has indicate ( so we left it until now).
We just did a quick modification to add indicate API to 0.8.x branch

https://github.com/adafruit/Adafruit_nR ... tree/0.8.x

It is mostly the same as notify() API

https://github.com/adafruit/Adafruit_nR ... tic.h#L151

Let's me know if it works for you. Once you confirm it works we will release it as 0.8.2

[jevada]

Thanks. I followed the recipe described in the git repo but it just kills my development environment. When done, it will no longer recognize the Feather nRF52 board at all. Is it enough to just copy ~/Adafruit_nRF52_Arduino/libraries/Bluefruit52Lib/src/BleCharacteristic.* or do I run into a lot of inconsistency problems than? I am on 0.8.1 now....

[hathach]

please follow the guide to manual install BSP via git

https://learn.adafruit.com/bluefruit-nr ... sp-via-git

[jevada]

Allright, first impression is it works. I didn't extensively test it, so I don't know for example what happens if the respons is not ack'd but it's enough for me.

Thanks!

[hathach]

Thanks, that is enough for it to be included in the next release.
We could fix bugs later (they appear anyway). Please let's everyone here know if you find one.

[jevada]

Will do.

In the meantime, I'm mightily impressed with the support you guys deliver! Top notch guys!

[hathach]

we just release 0.8.2 with indicate API. There is also a new example to demonstrate how to use it (basically the same as notify API).

https://github.com/adafruit/Adafruit_nR ... om_htm.ino