@codemaniac64 Umm I'm not sure, do you have any debug visibility on your PSoC code? Seems like it's rejecting something. Can you see if the BLE connection is still up when you try the .write(b'x0f')? It really helps to have a BLE sniffer like this https://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRF-Sniffer

@iber That's normal because it's not really a buffer, Bluetooth LE characteristics are usually restricted to 20 bytes by the protocol - it's what fits in the BLE packet - so unless you negotiate a larger MTU (larger packets than standard) between peers or use Long attributes you are restricted to that amount. Neither of those extended techniques are currently supported.

@jmahesh You are connecting to GATT Server as client, so what you can do is request the server send you notifications. You can't send notifications as a client. Bluetooth.PROP_NOTIFY means you can request notifications on that characteristic. I'm guessing that characteristic is not writable (read only) hence you get that error? If what you want is to be notified by the Server (e.g. when the value changes) use the char.callback(trigger=Bluetooth.CHAR_NOTIFY_EVENT, handler=YourHandlerFunct, arg=YourOptionalArgument)