Error Writing Large Characteristics

[Bill Finger]

I am working on a BLE peripheral. I have a large, variable length characteristic I need to set from the central.

When the central is the BTool, I can write up to the maximum size of my characteristic, which is 512 bytes. It carves it into 90 byte blocks, and sends them 18 bytes at a time.

When the central is Android, any write more than 18 bytes fails. In the onCharacteristicWrite callback I receive status 133 (GATT_ERROR).

Any ideas why I would get this error?

Edit 1: I also have a Windows client implementation. There, the function BluetoothGATTSetCharacteristicValue() returns 58, ERROR_BAD_NET_RESP, "The specified server cannot perform the requested operation.".

I have a test point that I set when I am copying the bytes from each packet into the blob. I can see that with both the Windows and Android implementations I am only getting the first packet.

[Petter Myhre]

I'm not an Android expert, but Aleksander Nowakowski is, and according to him it should work. How are you handling this in the peripheral application? If you have Sniffer traces, could you edit your question and upload them?

[Petter Myhre]

Great that you got it working.

1. Thank you for the feedback, I'll relay that to the developers, but which example are you referring to?

2. You should be able to calculate the size by using this.

3. This is an alternative. With this approach I guess you can copy the data in as it comes, but then if you get link loss only a part of the data may be valid.