Does BLE_GATTS_EVT_WRITE event not occur after BLE_GATTS_EVT_RW_AUTHORIZE_REQUEST?

[addngkr]

Hi, I am getting a BLE_GATTS_EVT_RW_AUTHORIZE_REQUEST event since I increased the size of MAX MTU to 203 from 23. At first, I received INVALID PARAM error and then found out from Q&As that there was a bug in SDK. Fixed the issue but now the device gets stuck after generating BLE_GATTS_OP_PREP_WRITE_REQ and BLE_GATTS_OP_EXEC_WRITE_REQ_CANCEL consecutively and BLE_GATTS_EVT_WRITE is never called. 

There are a couple of things I don't understand:

1. Why do I get AUTHORIZE event for MTU size 203 but not 23?

2. How do I write the data after authorization is complete? (I am not sure if I am right but, it seems that there's some data write field of ble_gatts_evt_rw_authorize_request_t struct during BLE_GATTS_OP_PREP_WRITE_REQ as data length was non-zero.)

I am using nRF5_SDK_14.0.0_3bcc1f7 and s132_nrf52_5.0.0_softdevice.hex

Thanks!

[Vidar Berg]

Hi,

I suspect the GATT client is attempting a Queued write operation (sometimes referred to as "long write". MSC: GATTS Queued Writes: App handled, no attributes require authorization). And the reason may be that it's not actually supporting a long MTU (>23 bytes) but still wants to update a characteristic value with more than "MTU" bytes. The  GATT Module should report the MTU size for a given link after negotiation to the app if you want to confirm this. 

You mentioned a bug in the SDK, was it in the Queued Writes module?

Another thread which may be relevant: https://devzone.nordicsemi.com/f/nordic-q-a/43045/trying-to-add-handler-for-ble_gatts_evt_rw_authorize_request-to-ble_app_blinky-but-get-invalid-state-from-authorize_reply/168492#168492