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81 lines
2.2 KiB
81 lines
2.2 KiB
4 years ago
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Respond to *sync* and *reset* events
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------------------------------------
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sync
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~~~~
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The NimBLE stack is inoperable while the host and controller are out of
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sync. In a combined host-controller app, the sync happens immediately at
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startup. When the host and controller are separate, sync typically
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occurs in under a second after the application starts. An application
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learns when sync is achieved by configuring the host's *sync callback*:
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``ble_hs_cfg.sync_cb``. The host calls the sync callback whenever sync
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is acquired. The sync callback has the following form:
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.. code-block:: cpp
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typedef void ble_hs_sync_fn(void);
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Because the NimBLE stack begins in the unsynced state, the application
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should delay all BLE operations until the sync callback has been called.
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reset
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~~~~~
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Another event indicated by the host is a *controller reset*. The NimBLE
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stack resets itself when a catastrophic error occurs, such as loss of
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communication between the host and controller. Upon resetting, the host
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drops all BLE connections and loses sync with the controller. After a
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reset, the application should refrain from using the host until sync is
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again signaled via the sync callback.
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An application learns of a host reset by configuring the host's *reset
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callback*: ``ble_hs_cfg.reset_cb``. This callback has the following
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form:
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.. code-block:: cpp
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typedef void ble_hs_reset_fn(int reason);
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The ``reason`` parameter is a :doc:`NimBLE host return
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code <../ble_hs/ble_hs_return_codes>`.
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Example
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~~~~~~~
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The following example demonstrates the configuration of the sync and
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reset callbacks.
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.. code-block:: cpp
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#include "sysinit/sysinit.h"
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#include "console/console.h"
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#include "host/ble_hs.h"
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static void
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on_sync(void)
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{
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/* Begin advertising, scanning for peripherals, etc. */
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}
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static void
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on_reset(int reason)
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{
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console_printf("Resetting state; reason=%d\n", reason);
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}
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int
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main(void)
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{
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/* Initialize all packages. */
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sysinit();
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ble_hs_cfg.sync_cb = on_sync;
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ble_hs_cfg.reset_cb = on_reset;
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/* As the last thing, process events from default event queue. */
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while (1) {
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os_eventq_run(os_eventq_dflt_get());
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}
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}
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