feature(split): add support for sensors from peripheral

This commit adds a new GATT characteristics on the peripheral side
and wires it up to read sensor values. The central side subscribes
to this new characteristics and replays sensor values on its side.

—

This commit was originally made by Stephen Wan. I just adjusted it so that it rebases on top of later changes on the zmk main branch.

app/include/zmk/split/bluetooth/service.h

@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <drivers/sensor.h>
+
 #define ZMK_SPLIT_RUN_BEHAVIOR_DEV_LEN 9
 
 struct zmk_split_run_behavior_data {
@@ -20,5 +22,7 @@ struct zmk_split_run_behavior_payload {
     char behavior_dev[ZMK_SPLIT_RUN_BEHAVIOR_DEV_LEN];
 } __packed;
 
+
 int zmk_split_bt_position_pressed(uint8_t position);
-int zmk_split_bt_position_released(uint8_t position);
+int zmk_split_bt_position_released(uint8_t position);
+int zmk_split_bt_sensor_triggered(uint8_t sensor_number, struct sensor_value value);

app/include/zmk/split/bluetooth/uuid.h

@@ -16,3 +16,4 @@
 #define ZMK_SPLIT_BT_SERVICE_UUID ZMK_BT_SPLIT_UUID(0x00000000)
 #define ZMK_SPLIT_BT_CHAR_POSITION_STATE_UUID ZMK_BT_SPLIT_UUID(0x00000001)
 #define ZMK_SPLIT_BT_CHAR_RUN_BEHAVIOR_UUID ZMK_BT_SPLIT_UUID(0x00000002)
+#define ZMK_SPLIT_BT_CHAR_SENSOR_STATE_UUID ZMK_BT_SPLIT_UUID(0x00000002)

app/src/split/bluetooth/central.c

@@ -20,10 +20,12 @@ LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 #include <zmk/stdlib.h>
 #include <zmk/ble.h>
 #include <zmk/behavior.h>
+#include <zmk/sensors.h>
 #include <zmk/split/bluetooth/uuid.h>
 #include <zmk/split/bluetooth/service.h>
 #include <zmk/event_manager.h>
 #include <zmk/events/position_state_changed.h>
+#include <zmk/events/sensor_event.h>
 #include <init.h>
 
 static int start_scan(void);
@@ -146,6 +148,50 @@ void peripheral_event_work_callback(struct k_work *work) {
 
 K_WORK_DEFINE(peripheral_event_work, peripheral_event_work_callback);
 
+#if ZMK_KEYMAP_HAS_SENSORS
+K_MSGQ_DEFINE(peripheral_sensor_event_msgq, sizeof(struct zmk_sensor_event),
+              CONFIG_ZMK_SPLIT_BLE_CENTRAL_POSITION_QUEUE_SIZE, 4);
+
+void peripheral_sensor_event_work_callback(struct k_work *work) {
+    struct zmk_sensor_event ev;
+    while (k_msgq_get(&peripheral_sensor_event_msgq, &ev, K_NO_WAIT) == 0) {
+        LOG_DBG("Trigger sensor change for %d", ev.sensor_number);
+        ZMK_EVENT_RAISE(new_zmk_sensor_event(ev));
+    }
+}
+
+K_WORK_DEFINE(peripheral_sensor_event_work, peripheral_sensor_event_work_callback);
+
+struct sensor_event {
+    uint8_t sensor_number;
+    struct sensor_value value;
+};
+
+static uint8_t split_central_sensor_notify_func(struct bt_conn *conn,
+                                                struct bt_gatt_subscribe_params *params,
+                                                const void *data, uint16_t length) {
+
+    const struct sensor_event *sensor_event = data;
+
+    if (!data) {
+        LOG_DBG("[UNSUBSCRIBED]");
+        params->value_handle = 0U;
+        return BT_GATT_ITER_STOP;
+    }
+    LOG_DBG("[SENSOR NOTIFICATION] data %p length %u", data, length);
+
+    struct zmk_sensor_event ev = {
+        .sensor_number = sensor_event->sensor_number,
+        .value = {.val1 = (sensor_event->value).val1, .val2 = (sensor_event->value).val2},
+        .timestamp = k_uptime_get()};
+
+    k_msgq_put(&peripheral_sensor_event_msgq, &ev, K_NO_WAIT);
+    k_work_submit(&peripheral_sensor_event_work);
+
+    return BT_GATT_ITER_CONTINUE;
+}
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+
 static uint8_t split_central_notify_func(struct bt_conn *conn,
                                          struct bt_gatt_subscribe_params *params, const void *data,
                                          uint16_t length) {
@@ -205,6 +251,39 @@ static void split_central_subscribe(struct bt_conn *conn, struct bt_gatt_subscri
     }
 }
 
+#if ZMK_KEYMAP_HAS_SENSORS
+static struct bt_uuid_128 sensor_uuid = BT_UUID_INIT_128(ZMK_SPLIT_BT_SERVICE_UUID);
+static struct bt_gatt_discover_params sensor_discover_params;
+static struct bt_gatt_subscribe_params sensor_subscribe_params;
+static uint8_t split_central_sensor_desc_discovery_func(struct bt_conn *conn,
+                                                        const struct bt_gatt_attr *attr,
+                                                        struct bt_gatt_discover_params *params) {
+    int err;
+
+    if (!bt_uuid_cmp(sensor_discover_params.uuid,
+                     BT_UUID_DECLARE_128(ZMK_SPLIT_BT_CHAR_SENSOR_STATE_UUID))) {
+        memcpy(&sensor_uuid, BT_UUID_GATT_CCC, sizeof(sensor_uuid));
+        sensor_discover_params.uuid = &sensor_uuid.uuid;
+        sensor_discover_params.start_handle = attr->handle;
+        sensor_discover_params.type = BT_GATT_DISCOVER_DESCRIPTOR;
+
+        sensor_subscribe_params.value_handle = bt_gatt_attr_value_handle(attr);
+
+        err = bt_gatt_discover(conn, &sensor_discover_params);
+        if (err) {
+            LOG_ERR("Discover failed (err %d)", err);
+        }
+    } else {
+        sensor_subscribe_params.notify = split_central_sensor_notify_func;
+        sensor_subscribe_params.value = BT_GATT_CCC_NOTIFY;
+        sensor_subscribe_params.ccc_handle = attr->handle;
+        split_central_subscribe(conn, &sensor_subscribe_params);
+    }
+
+    return BT_GATT_ITER_STOP;
+}
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+
 static uint8_t split_central_chrc_discovery_func(struct bt_conn *conn,
                                                  const struct bt_gatt_attr *attr,
                                                  struct bt_gatt_discover_params *params) {
@@ -282,6 +361,22 @@ static uint8_t split_central_service_discovery_func(struct bt_conn *conn,
     if (err) {
         LOG_ERR("Failed to start discovering split service characteristics (err %d)", err);
     }
+
+#if ZMK_KEYMAP_HAS_SENSORS
+        memcpy(&sensor_uuid, BT_UUID_DECLARE_128(ZMK_SPLIT_BT_CHAR_SENSOR_STATE_UUID),
+               sizeof(sensor_uuid));
+        sensor_discover_params.uuid = &sensor_uuid.uuid;
+        sensor_discover_params.start_handle = attr->handle;
+        sensor_discover_params.end_handle = 0xffff;
+        sensor_discover_params.type = BT_GATT_DISCOVER_CHARACTERISTIC;
+        sensor_discover_params.func = split_central_sensor_desc_discovery_func;
+
+        err = bt_gatt_discover(conn, &sensor_discover_params);
+        if (err) {
+            LOG_ERR("Discover failed (err %d)", err);
+        }
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+
     return BT_GATT_ITER_STOP;
 }
 

app/src/split/bluetooth/service.c

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: MIT
  */
 
+#include <drivers/sensor.h>
 #include <zephyr/types.h>
 #include <sys/util.h>
 #include <init.h>
@@ -20,6 +21,23 @@ LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 #include <zmk/matrix.h>
 #include <zmk/split/bluetooth/uuid.h>
 #include <zmk/split/bluetooth/service.h>
+#include <zmk/sensors.h>
+
+#if ZMK_KEYMAP_HAS_SENSORS
+struct sensor_event {
+    uint8_t sensor_number;
+    struct sensor_value value;
+} sensor_event;
+
+static ssize_t split_svc_sensor_state(struct bt_conn *conn, const struct bt_gatt_attr *attrs,
+                                      void *buf, uint16_t len, uint16_t offset) {
+    return bt_gatt_attr_read(conn, attrs, buf, len, offset, &sensor_event, sizeof(sensor_event));
+}
+
+static void split_svc_sensor_state_ccc(const struct bt_gatt_attr *attr, uint16_t value) {
+    LOG_DBG("value %d", value);
+}
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
 
 #define POS_STATE_LEN 16
 
@@ -98,7 +116,14 @@ BT_GATT_SERVICE_DEFINE(
                            BT_GATT_CHRC_WRITE_WITHOUT_RESP, BT_GATT_PERM_WRITE_ENCRYPT, NULL,
                            split_svc_run_behavior, &behavior_run_payload),
     BT_GATT_DESCRIPTOR(BT_UUID_NUM_OF_DIGITALS, BT_GATT_PERM_READ, split_svc_num_of_positions, NULL,
-                       &num_of_positions), );
+                       &num_of_positions),
+#if ZMK_KEYMAP_HAS_SENSORS
+    BT_GATT_CHARACTERISTIC(BT_UUID_DECLARE_128(ZMK_SPLIT_BT_CHAR_SENSOR_STATE_UUID),
+                           BT_GATT_CHRC_READ | BT_GATT_CHRC_NOTIFY, BT_GATT_PERM_READ_ENCRYPT,
+                           split_svc_sensor_state, NULL, &sensor_event),
+    BT_GATT_CCC(split_svc_sensor_state_ccc, BT_GATT_PERM_READ_ENCRYPT | BT_GATT_PERM_WRITE_ENCRYPT),
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+);
 
 K_THREAD_STACK_DEFINE(service_q_stack, CONFIG_ZMK_SPLIT_BLE_PERIPHERAL_STACK_SIZE);
 
@@ -151,6 +176,51 @@ int zmk_split_bt_position_released(uint8_t position) {
     return send_position_state();
 }
 
+#if ZMK_KEYMAP_HAS_SENSORS
+K_MSGQ_DEFINE(sensor_state_msgq, sizeof(sensor_event),
+              CONFIG_ZMK_SPLIT_BLE_PERIPHERAL_POSITION_QUEUE_SIZE, 4);
+
+void send_sensor_state_callback(struct k_work *work) {
+    struct sensor_event ev;
+
+    while (k_msgq_get(&sensor_state_msgq, &ev, K_NO_WAIT) == 0) {
+        int err = bt_gatt_notify(NULL, &split_svc.attrs[5], &ev, sizeof(ev));
+        if (err) {
+            LOG_DBG("Error notifying %d", err);
+        }
+    }
+};
+
+K_WORK_DEFINE(service_sensor_notify_work, send_sensor_state_callback);
+
+int send_sensor_state() {
+    int err = k_msgq_put(&sensor_state_msgq, &sensor_event, K_MSEC(100));
+    if (err) {
+        // retry...
+        switch (err) {
+        case -EAGAIN: {
+            LOG_WRN("Sensor state message queue full, popping first message and queueing again");
+            struct sensor_event discarded_state;
+            k_msgq_get(&sensor_state_msgq, &discarded_state, K_NO_WAIT);
+            return send_sensor_state();
+        }
+        default:
+            LOG_WRN("Failed to queue sensor state to send (%d)", err);
+            return err;
+        }
+    }
+
+    k_work_submit_to_queue(&service_work_q, &service_sensor_notify_work);
+    return 0;
+}
+
+int zmk_split_bt_sensor_triggered(uint8_t sensor_number, struct sensor_value value) {
+    sensor_event.sensor_number = sensor_number;
+    sensor_event.value = value;
+    return send_sensor_state();
+}
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+
 int service_init(const struct device *_arg) {
     static const struct k_work_queue_config queue_config = {
         .name = "Split Peripheral Notification Queue"};

app/src/split_listener.c

@@ -5,6 +5,7 @@
  */
 
 #include <device.h>
+#include <drivers/sensor.h>
 #include <logging/log.h>
 
 #include <zmk/split/bluetooth/service.h>
@@ -13,21 +14,38 @@ LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 
 #include <zmk/event_manager.h>
 #include <zmk/events/position_state_changed.h>
+#include <zmk/events/sensor_event.h>
 #include <zmk/hid.h>
+#include <zmk/sensors.h>
 #include <zmk/endpoints.h>
 
 int split_listener(const zmk_event_t *eh) {
     LOG_DBG("");
-    const struct zmk_position_state_changed *ev = as_zmk_position_state_changed(eh);
+    const struct zmk_position_state_changed *pos_ev;
-    if (ev != NULL) {
+    if ((pos_ev = as_zmk_position_state_changed(eh)) != NULL) {
-        if (ev->state) {
+        if (pos_ev != NULL) {
-            return zmk_split_bt_position_pressed(ev->position);
+            if (pos_ev->state) {
-        } else {
+                return zmk_split_bt_position_pressed(pos_ev->position);
-            return zmk_split_bt_position_released(ev->position);
+            } else {
+                return zmk_split_bt_position_released(pos_ev->position);
+            }
         }
     }
+
+#if ZMK_KEYMAP_HAS_SENSORS
+    const struct zmk_sensor_event *sensor_ev;
+    if ((sensor_ev = as_zmk_sensor_event(eh)) != NULL) {
+        if (sensor_ev != NULL) {
+            return zmk_split_bt_sensor_triggered(sensor_ev->sensor_number, sensor_ev->value);
+        }
+    }
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
     return ZMK_EV_EVENT_BUBBLE;
 }
 
 ZMK_LISTENER(split_listener, split_listener);
-ZMK_SUBSCRIPTION(split_listener, zmk_position_state_changed);
+ZMK_SUBSCRIPTION(split_listener, zmk_position_state_changed);
+
+#if ZMK_KEYMAP_HAS_SENSORS
+ZMK_SUBSCRIPTION(split_listener, zmk_sensor_event);
+#endif /* ZMK_KEYMAP_HAS_SENSORS */