iOS peripheral and nRF51822 central writing char

[d4nk]

Hello,

Situation:

I am trying to write a characteristic to an iOS device acting as a peripheral from a nRF51822 board. The board has 2 leds (green and red) and a button.

The iOS device is running an app exposing a service (let's say it's ID is XXXX) and it has one characteristic (YYYY).

The nRF board does the following steps when I push the button:

1. Scan for any peripheral exposing the service XXXX.
2. Once if finds it (BLE_GAP_EVT_ADV_REPORT) I check that the char UUID is being advertised.
3. Stop scan and connect (using sd_ble_gap_scan_stop and sd_ble_gap_connect).
4. Once I get the BLE_GAP_EVT_CONNECTED I start a discovery using ble_db_discovery_start.
5. When I receive the BLE_DB_DISCOVERY_COMPLETE and after checking the UUID, I use a for to find the char (YYYY).
6. Finally if I find the char I write 20 bytes to it (sd_ble_gattc_write and BLE_GATT_OP_WRITE_REQ).
7. Once I receive the BLE_GATTC_EVT_WRITE_RSP event, I turn the green led on.

On every step of the process, if any function called returns an error or if I get an event like BLE_GAP_EVT_TIMEOUT or something that indicates something is wrong, I turn the red led on.

The problem:

When I run the app on the iOS device and I press the button on the board, the green led turns on. This shows that the char has been written successfully but the callback peripheralManager:didReceiveWriteRequests: is never called on the iOS device.

On one hand, it looks like it has been written from the board side but on the other I never receive the information on the iOS device.

What I tried:

• I changed the characteristic and service UUIDs on the iOS device to check that the board is finding the correct char, I get a red light what means that it is right with the correct values.
• I turned the iOS bluetooth off, I get a red light.
• I tried using another iOS device to write the same characteristic (YYYY) and I can write it correctly (the callback gets called).
• I tried using BLE_GATT_OP_WRITE_CMD instead of BLE_GATT_OP_WRITE_REQ and the same thing happens (I also set CBCharacteristicPropertyWriteWithoutResponse and CBCharacteristicPropertyWrite values on the iOS device to be sure).

I am kinda stuck here, I would try to use a sniffer or something to check the traffic, but I think that the problem is something I am missing here.

Any clues??

Thanks for reading!

[d4nk]

Well, first of all, sorry for wasting your time.

Sometimes happens that after a some days trying to make it work and then going to the forums to post the question, just a couple of minutes later you find the solution.

I will post the solution here for anyone with the same problem:

I just used the characteristic CCCD handle (charateristics[i].cccd_handle) instead of the characteristic handle value (charateristics[i].characteristic.handle_value) when filling the sd_ble_gattc_write params handle.

[Ulrich Myhre]

Rubber Duck Debugging sometimes work out :) Good that you found your solution!