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

[Petter Myhre]

I see. If I were you I would do a sniffer trace of the communication with iOS and with the S120. Then you can see what iOS is doing differently. You can use the nRF Sniffer to do this. If you have trouble analyzing the traces you can edit your question and upload them there, and I'll take a look. Level 3 is supported, but with Passkey Entry both devices need to have keyboard or display, and with OOB you need to transfer a key in another medium like NFC. iOS doesn't use OOB, and it would have asked you to enter a passkey if passkey entry was used.