feat: only send HID reports to one endpoint

Added some utility functions and an event for tracking the state of the
USB connection.

Updated endpoints.c to select a single endpoint to send HID reports to
based on the status of the USB and BLE connections. Partially fixes #206.

Future commits will add a user setting to control which endpoint is used if
both USB and BLE are ready.

2 files changed, 31 insertions, 1 deletions

diff --git a/app/include/zmk/events/usb-conn-state-changed.h b/app/include/zmk/events/usb-conn-state-changed.h
new file mode 100644
index 0000000..d6cc698
--- /dev/null
+++ b/app/include/zmk/events/usb-conn-state-changed.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <zephyr.h>
+#include <usb/usb_device.h>
+
+#include <zmk/event-manager.h>
+#include <zmk/usb.h>
+
+struct usb_conn_state_changed {
+    struct zmk_event_header header;
+    enum zmk_usb_conn_state conn_state;
+};
+
+ZMK_EVENT_DECLARE(usb_conn_state_changed);
\ No newline at end of file
diff --git a/app/include/zmk/usb.h b/app/include/zmk/usb.h
index 452fd54..30461de 100644
--- a/app/include/zmk/usb.h
+++ b/app/include/zmk/usb.h
@@ -12,8 +12,18 @@
 #include <zmk/keys.h>
 #include <zmk/hid.h>
 
+enum zmk_usb_conn_state {
+    ZMK_USB_CONN_NONE,
+    ZMK_USB_CONN_POWERED,
+    ZMK_USB_CONN_HID,
+};
+
 enum usb_dc_status_code zmk_usb_get_status();
+enum zmk_usb_conn_state zmk_usb_get_conn_state();
+
+static inline bool zmk_usb_is_powered() { return zmk_usb_get_conn_state() != ZMK_USB_CONN_NONE; }
+static inline bool zmk_usb_is_hid_ready() { return zmk_usb_get_conn_state() == ZMK_USB_CONN_HID; }
 
 #ifdef CONFIG_ZMK_USB
-int zmk_usb_hid_send_report(u8_t *report, size_t len);
+int zmk_usb_hid_send_report(const u8_t *report, size_t len);
 #endif /* CONFIG_ZMK_USB */
\ No newline at end of file