How send large notification?

[CheMax]

Hello, In our project we want use a large characteristic with notification property.

I use a "ble_app_template" project from nRF5_SDK_14.2.0_17b948a\examples\ble_peripheral. In a project i added custom service with one characterics, it's length 200 byte. Property: Read;Write;Notification.

And I changed MTU size to 247.

So, as "master" I use Ubuntu PC with BlueZ stack. For connect uses "gatttool utility". After success connect in RTT i see:

<debug> nrf_sdh_ble: BLE event: 0x10.
<debug> ble_gatt: Requesting to update ATT MTU to 247 bytes on connection 0x0.
<debug> ble_gatt: Requesting to update data length to 251 on connection 0x0.
<info> app: Connected.
<debug> nrf_sdh_ble: BLE event: 0x24.
<debug> ble_gatt: Data length updated to 27 on connection 0x0.
<debug> ble_gatt: max_rx_octets: 27
<debug> ble_gatt: max_tx_octets: 27
<debug> ble_gatt: max_rx_time: 328
<debug> ble_gatt: max_tx_time: 328
<debug> nrf_sdh_ble: BLE event: 0x3A.
<debug> ble_gatt: ATT MTU updated to 23 bytes on connection 0x0 (response).
<debug> nrf_sdh_ble: BLE event: 0x12.

after in gatt tool i send command: mtu 247 for increase mtu size. In RTT added next:

<debug> nrf_sdh_ble: BLE event: 0x55.
<debug> ble_gatt: Peer on connection 0x0 requested an ATT MTU of 247 bytes.
<debug> ble_gatt: Updating ATT MTU to 247 bytes (desired: 247) on connection 0x0.

When I read a characterictics, I see all 200 bytes. But, If i enable notification, i receive only 20 bytes.

I don't understand, What have I forgotten to do yet?

P.S. Keil MDK, HW: PCA10040 v1.1.0, SW: S132

[00]ble_app_template.rar

Thanks, Best Regurds Max

[Petter Myhre]

How are you sending the notification? Are you sure you are not sending 20 bytes?

[CheMax]

I changed example add custom service. the next part of the code is used for sending

gatts_value.len     = 200;
    gatts_value.offset  = 0;
    gatts_value.p_value = custom_value;

    // Update database.
err_code = sd_ble_gatts_value_set(p_cus->conn_handle,
                                  p_cus->custom_value_handles.value_handle,
                                  &gatts_value);

hvx_params.handle = p_cus->custom_value_handles.value_handle;
    hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;
    hvx_params.offset = gatts_value.offset;
    hvx_params.p_len  = &gatts_value.len;
    hvx_params.p_data = gatts_value.p_value;
    err_code = sd_ble_gatts_hvx(p_cus->conn_handle, &hvx_params);

[Petter Myhre]

You don't need to callsd_ble_gatts_value_set() first. Anyways, looks okay. And sd_ble_gatts_hvx() returns 0x00000000 (NRF_SUCCESS)? Do you have sniffer trace of the communication that I can look at? Have you tested with any other centrals?

[CheMax]

1. yes, it's return success;
2. with sniffer i have another problem (The sniffer does not capture packets (the shark does not show anything, after a long pause produces an error) or stops sending data to the shark after a short recording of the advertisement packets. I tried both versions and different boards, the behavior is the same).
3. No, I test only with ubuntu (blueZ, gatttool) and nrfconnect (win8)

why I shouldd't call sd_ble_gatts_value_set() first?

[Petter Myhre]

2. Then you should post another question describing your issues.

3. Do you see the same behavior with nRF Connect and Win8?

Because it is not necessary to call sd_ble_gatts_value_set() to send a notification. You provide the data you want in the notification when you call sd_ble_gatts_hvx()

I can also test your project here if you want to, then you need to upload your complete project to the question.