Required buffer data on cccd_handle write for INDICATION

[Mark Paul]

Hello,

I'm working with a nrf51822, SoftDevice S120 v2.0 and SDK v9.0 platform.

Specifically using it a Central role to connect to a Blood Pressure peripheral.

I connect to the peripheral, find the Service/Characteristic I need and register for an "Indication" like so:

uint32_t                 err_code;
ble_gattc_write_params_t write_params;
uint8_t                  buf[BLE_CCCD_VALUE_LEN];

buf[0] = BLE_GATT_HVX_INDICATION;
buf[1] = 0;

write_params.write_op = BLE_GATT_OP_WRITE_REQ;
write_params.handle   = p_client->srv_db.services[0].charateristics[p_client->my_char_index].cccd_handle;
write_params.offset   = 0;
write_params.len      = sizeof(buf);
write_params.p_value  = buf;

err_code = sd_ble_gattc_write(p_client->srv_db.conn_handle, &write_params);
APP_ERROR_CHECK(err_code);

Unfortunately this does not work for me.

i.e. I get a BLE_GATTC_EVT_WRITE_RSP back from the peripheral but BLE_GATTC_EVT_HVX never gets throw to indicate data has been received.

In this:

buf[0] = BLE_GATT_HVX_INDICATION;
buf[1] = 0

Can someone please tell me what buf[1] = 0 is supposed to be? I copied this from a NOTIFICATION example and I cant seem to find anywhere in the documentation what this buffer is supposed to contain. I suspect this may have something to do with the problem.

Thanks very much, Mark

[Mark Paul]

Hi @Petter

Yes its a commercial blood pressure monitor which I have the API for. The API documentation does not mention anything about security levels.

In fact, I built an iOS app that connects and reads the data from the peripheral and it worked using the standard iOS bluetooth modules (i.e. the pairing and security etc was taken care on a simple connect() request without me writing any custom code or config to handle security). I assumed the Device Manager would handle this in a similar way too.

Does the DM default to Level 2? is there some setting I can update to try Level 3 and 4?