NRF51822 peripheral keep it invisible

RE: NRF51822 peripheral keep it invisible

awneil — Thu, 03 Mar 2016 07:37:28 GMT

nRF51 SDK 10.0.0 main page:

developer.nordicsemi.com/.../

At the bottom is, "User guides for Gazell and Enhanced ShockBurst" - which says:

The examples have been grouped with S110 documentation but will work with any SoftDevice

(my emphasis).

RE: NRF51822 peripheral keep it invisible

FormerMember — Thu, 03 Mar 2016 07:31:01 GMT

Yes, @awneil says, it may be a better solution to combine the BLE with another protocol. You can for example combine BLE with the Nordic proprietary protocol "Gazll"- You can find an an example of that in the following folder in the SDK: ..\nRF51_SDK_10.0.0_dc26b5e\examples\multiprotocol\ble_app_gzll (I will update this in the "main" answer as well.)

RE: NRF51822 peripheral keep it invisible

awneil — Wed, 02 Mar 2016 18:13:15 GMT

Of course there are many possible solutions!

The NRF51822 can support other 2.4GHz protocols. I think it can do both BT and "proprietary" at the same time?

Clearly, one device can only wake another if it is "listening"...

RE: NRF51822 peripheral keep it invisible

toashwin — Wed, 02 Mar 2016 17:16:32 GMT

Are there any alternate solutions possible? On the hub, I need the BT to connect to the phone. As such, I am thinking of using same BT to connect to the peripherals.

Also, so far I did not come across a solution, where a peripheral can wake up another device. Even with NRF24, the the sleeping device need to wake in intervals scan for available transmits and go to sleep.

RE: NRF51822 peripheral keep it invisible

awneil — Wed, 02 Mar 2016 15:36:22 GMT

It is not possible for the peripheral devices to wake up the central device...

This is an inherent part of the way BT works

The 4 peripherals should NOT be visible on the cell-phone

So why use BT for the 4 peripherals at all? Especially, as noted above, given that some of your requirements do not fit the way BT works anyhow?

RE: NRF51822 peripheral keep it invisible

FormerMember — Wed, 02 Mar 2016 14:46:08 GMT

1) When a central (the hub) scans for advertising devices it will receive the adverting data in advertising reports. It then possible to "inspect" the advertising report and check the name of the device, and then, if the name matches the pre-defined name, initiate a connection. That is what the ble_app_mulilink example in the SDK does, see the below code snippet from main.c:

static void on_ble_evt(ble_evt_t * p_ble_evt)
{
uint32_t        err_code;

switch (p_ble_evt->header.evt_id)
{
    case BLE_GAP_EVT_ADV_REPORT:
    {
    ...
    ...
    ...
        // Verify if short or complete name matches target.
        if ((err_code == NRF_SUCCESS) &&
           (0 == memcmp(TARGET_DEV_NAME,type_data.p_data,type_data.data_len)))
        {
            err_code = sd_ble_gap_scan_stop();
            if (err_code != NRF_SUCCESS)
            {
                APPL_LOG("[APPL]: Scan stop failed, reason %d\r\n", err_code);
            }

            // Initiate a connection if the name matches the pre-defined name:
            err_code = sd_ble_gap_connect(&p_ble_evt->evt.gap_evt.params.adv_report.\
                                          peer_addr,
                                          &m_scan_param,
                                          &m_connection_param);
    ...
    ...
    ...

2) By using directed advertising, no other centrals then the one specified in the advertising data may initiate a connection. Directed advertising is described in the Bluetooth Core Specification v.4.2, Vol. 6, Part B, chapter 4.4.2.4.

3) It is not possible for the peripheral devices to wake up the central device; when there is no connection, it is the central that scan for peripherals.

To save as much power as possible you can use slave latency and the longest possible connection interval, see explanation in this thread.

4) Yes, it should be perfectly possible to get 10 to 20 m range.

Update 03.03.16: Another solution could be to combine BLE with another protocol. You can for example combine BLE with the Nordic proprietary protocol "Gazll". You can find an an example of that in the following folder in the SDK: ..\nRF51_SDK_10.0.0_dc26b5e\examples\multiprotocol\ble_app_gzll