debugging sd_ble_gatts_hvx

[wim]

Hi

I am trying to get to the bottom of a problem I am having with sending a buffer of data on connection and indication enable. Here's what I do: I have a process running, which is capturing sensor data every 10 seconds, and keeping it in a circular buffer. When a master connects, I want to send the circular buffer to the master app. I am doing that by triggering on the event that the CCCD is written to enable indications (I am using indication because I want to make sure that the values end up in the app). When this CCCD write is happening, I send the first item in my circular buffer, and then use the BLE_GATTS_EVT_HVC event to see if I have gotten a confirmation, just as in the health thermometer example.

I am running into a number of problems

• when I trigger on the CCCD write and immediately do a sd_ble_gatts_hvx, I get an error 8 (illegal state); if I start a timer and do the same after 10 ms, then it is ok
• I sometimes also have a BLE_ERROR_GATTS_SYS_ATTR_MISSING error, how can I avoid that? when should I normally do a sd_ble_gatts_sys_attr_set(m_conn_handle, NULL, 0) (i do not use bonding)

I have the impression that timing issues or race conditions are causing my problems, can anyone give me hint on how to solve this?

[wim]

So maybe I describe in short again what I got: I changed my code such that on a BLE_GAP_EVT_CONNECTED event I do a sd_ble_gatts_sys_attr_set.

When I then wait on a write with value 2 to the CCCD of the characteristic I want to send indications from to the master. In the event handler of that write event, I immediately do a first sd_ble_gatts_hvx, hoping that I will get a BLE_GATTS_EVT_HVC when that indication was finished, such that on that event I can do a next sd_ble_gatts_hvx call, and so on, until my sample buffer I want to transmit is empty. However, when doing the first sd_ble_gatts_hvx I get a return value of NRF_ERROR_INVALID_STATE, and I never receive the confirmation of my indication. What can be the cause of the invalidi state? So I am connected, and the CCCD is written with the right value. Please help...