How to output the "instantaneous cadence" data from Cycling Speed and Cadence sensor (CSCS) example through nRF52-DK ?

[IDin]

Hi, all,

At first, I have to say I am a newbie in programming for BLE. ^^"

I trying to development a cycling power meter, so I want to modify this CSCS example to CPS, and it already roughly worked. 

I can connect and output instantaneous power(W) data to some devices now, just like cycling game Rouvy and Zwift through BLE connect.

nRF5-SDK V17.0.2    Segger Embedded Studio   OS:Windows-X64

In this example using the Service is "BLE_UUID_CYCLING_SPEED_AND_CADENCE  0x1816".

I checked GATT spec. supplement V5 document, it supports 3 features:

1.wheel revolution data supported

2.crank revolution data supported

3.multiple sensor locations supported

In crank revolution data support, I just found 2 flags:

1.Cumulative Crank Revolutions

2.Last Crank Event Time

How make it can output instantaneous cadence data to my device? just like android phone (app: nRF connect)?

[Sigurd]

Hi,

How make it can output instantaneous cadence data to my device?

What do you mean by output? You want to print the value over UART ? or send the data more frequently over BLE ?

[IDin]

Hi, Sigurd,

Thanks for your reply.

I means I need to send the instantaneous cadence data (RPM) just like I set up a cycling cadence sensor on bike and connect it to my android apps.

Makes app (Wahoo, Rouvy or others...) can receiving the RPM data correctly.

TT_Power is what I named to my nRF52-DK TX device, you can see it when I connected to this app (Rouvy).

App can receiving the instantaneous power data in 60W, but no instantaneous cadence data (that what I need).

 

[Sigurd]

From your android app, you need to enable notification for this characteristic, and then the nRF52 will start sending the data.

[IDin]

Hi, Sigurd,

I think that just what I need, but I don't know how to do it.

Can you tell me more details about enable notification for this characteristic? 

or can I get some examples for this?

[IDin]

I need make my nRF52-DK TX device always keep sending the data, when I connected it to other RX device over BLE.

So, back to my question,

I already calculated a numeral data, it named "instantaneous_cadence" in CSCS example,but I just can advertising the service "BLE_UUID_CYCLING_SPEED_AND_CADENCE  0x1816" supported feature data, like Cumulative Wheel Revolutions, Last Wheel Event Time, Cumulative Crank Revolutions and Last Crank Event Time.

but I don't know how to advertising others data (user defined data, like I created "instantaneous_cadence" or something others)  in this CSCS example.

[Sigurd]

IDin said:

Can you tell me more details about enable notification for this characteristic? 

I think you can use the function setCharacteristicNotification() for that. https://developer.android.com/reference/android/bluetooth/BluetoothGatt

We have several android libraries and example codes in different repos that you might find useful here: https://github.com/NordicSemiconductor?q=android&type=&language=&sort=

Also, looking at the Cycling Speed and Cadence Profile 1.0, https://www.bluetooth.com/specifications/specs/cycling-speed-and-cadence-profile-1-0/ , it looks like the calculation should be done at the collector side(e.g. phone), and not at the sensor side: