Disable HID some of the time

RE: Disable HID some of the time

khodidas — Fri, 30 Oct 2020 12:25:31 GMT

Hello Nick,

You mentioned

"We have an existing device on a different platform which already implements this. When switching between HID and non-HID modes, it will modify the HID report and send a services modified indication for the HID service, causing iOS to re-read the HID report. This works fine."

Please if you can inform us

(1) is that worked for you with nordic solution in iOS?

(2) was that working for you with different platform for android OS, where you modify the HID report from keyboard to any other one and android phone still recognize it as keyboard Vs non-keyboard device? You mentioned that iOS re-read the HID report and working fine. But does same works well for android ?

Regards,

khodidas

RE: Disable HID some of the time

nrbrook — Wed, 04 Sep 2019 11:13:35 GMT

There is a way to find this information, here is a function that will determine the end handle for a given service handle:

ret_code_t get_service_end_handle(uint16_t service_handle, uint16_t *end_handle) {
    VERIFY_PARAM_NOT_NULL(end_handle);
    ret_code_t err_code = NRF_SUCCESS;
    for (uint16_t handle = service_handle + 1; handle < UINT16_MAX; handle++) {
        ble_uuid_t uuid;
        err_code = sd_ble_gatts_attr_get(handle, &uuid, NULL);
        if (err_code == NRF_ERROR_NOT_FOUND) {
            *end_handle = handle - 1;
            return NRF_SUCCESS;
        }
        VERIFY_SUCCESS(err_code);
        if (uuid.type != BLE_UUID_TYPE_BLE ||
            (uuid.uuid != BLE_UUID_SERVICE_PRIMARY && uuid.uuid != BLE_UUID_SERVICE_SECONDARY)) {
            continue;
        }
        *end_handle = handle - 1;
        return NRF_SUCCESS;
    }
    *end_handle = UINT16_MAX;
    return NRF_ERROR_NOT_FOUND;
}

This end handle can then be passed to sd_ble_gatts_service_changed:

ret_code_t service_changed(uint16_t conn_handle, uint16_t service_handle) {
    uint16_t service_end;
    (void)get_service_end_handle(service_handle, &service_end);
    return sd_ble_gatts_service_changed(conn_handle, service_handle, service_end);
}

RE: Disable HID some of the time

Simonr — Thu, 08 Aug 2019 08:10:00 GMT

Hi Nick

Sorry, there doesn't seem to be a way to find this in the peripheral. However, while scouring the DevZone, I found this case, which describes how to use the sd_ble_gatts_service_changed. Please check out Pål's answers, as they are very descriptive.

Best regards,

Simon

RE: Disable HID some of the time

nrbrook — Wed, 07 Aug 2019 10:33:55 GMT

That's just for centrals though, correct? I was asking if there was a way to determine the service end handle programmatically in the peripheral to pass to

sd_ble_gatts_service_changed

RE: Disable HID some of the time

Simonr — Wed, 07 Aug 2019 09:28:07 GMT

Hi Nick

You should be able to find the HID service end handle, by printing end_handle from SD_BLE_GATTC_PRIMARY_SERVICES_DISCOVER. Please use the message sequence chart and this thread for reference. The database discovery module documentation should also be helpful for understanding the module itself.

Best regards,

Simon

RE: Disable HID some of the time

nrbrook — Mon, 05 Aug 2019 17:50:20 GMT

This is what I was wanting originally, as I mentioned sending a services changed indication for the existing HID service causes the OS to re-read the HID report, and if the report does not contain a keyboard then the virtual keyboard will be shown. Is there any way to determine the HID service end handle? or would it be a case of adding an offset to the final characteristic handle?

RE: Disable HID some of the time

Simonr — Mon, 05 Aug 2019 07:53:39 GMT

Hi Nick

sd_ble_gatts_service_changed is used to perform a Service Changed Indication to one or more peers. You can add and change services, but you won't be able to remove any. I'm not entirely sure how this works with HID, but I imagine "removing" the HID function might count as removing a service. In any case, you're welcome to try it out, and yes, you can use 0xFFFF as the end handle if you're not adding any further services.

Best regards,

Simon

RE: Disable HID some of the time

nrbrook — Fri, 02 Aug 2019 12:38:48 GMT

Actually there is the function

sd_ble_gatts_service_changed

You can pass a start handle and end handle. The start handle of the service is provided when creating. How can I get the end handle? Or perhaps I can just pass 0xFFFF if the service is the last service to be added?

RE: Disable HID some of the time

nrbrook — Fri, 02 Aug 2019 11:55:41 GMT

It isn't as fast, and we have our own services which would be interrupted by disconnection which then requires rediscovery on reconnection. If going from non-HID to HID mode, bonding would not exist as bonding will not be required in non-HID modes.

RE: Disable HID some of the time

Simonr — Fri, 02 Aug 2019 11:52:42 GMT

I asked around in the support team, and as far as we know, and based on what I've seen in various posts on Devzone. No, there isn't. Although I don't see why disconnecting between these "modes" would be a problem, when bonded, the device should be able to reconnect automatically after the reinitialize.

Best regards,

Simon

RE: Disable HID some of the time

nrbrook — Fri, 02 Aug 2019 11:44:13 GMT

Ok thanks, so there is no way I can force a service changed indication to be sent?

RE: Disable HID some of the time

Simonr — Fri, 02 Aug 2019 11:42:01 GMT

Hi Nick

I don't think this will be attainable without disconnecting due to the modification limitation you mentioned. We can send a service indication, HID report, etc. but disconnecting and reinitializing the SoftDevice with the new attribute table will be necessary.

Best regards,

Simon