report battery levels with bluetooth

firmware/app/prj.conf

@@ -23,6 +23,7 @@ CONFIG_BT_SMP=y
 CONFIG_BT_PERIPHERAL=y
 CONFIG_BT_GATT_CLIENT=y
 CONFIG_BT_DEVICE_NAME="Mellifera"
+CONFIG_BT_BAS=y
 
 CONFIG_BT_BUF_ACL_RX_SIZE=255
 CONFIG_BT_BUF_ACL_TX_SIZE=251

firmware/app/src/main.c

@@ -2,6 +2,7 @@
 #include <zephyr/drivers/sensor.h>
 #include <zephyr/logging/log.h>
 #include <zephyr/display/cfb.h>
+#include <zephyr/bluetooth/services/bas.h>
 
 #include <app/drivers/blink.h>
 
@@ -312,7 +313,11 @@ int thread_sensors(void)
 			LOG_ERR("Could not get sample");
 		}
 
-		sprintf(str_v, "V :%7.5f", voltage.val1 + voltage.val2 * 1e-6);
+		double vbat = voltage.val1 + voltage.val2 * 1e-6;
+		uint8_t pct_bat = 100.0 * (vbat - 3.3) / (4.2 - 3.3);
+		bt_bas_set_battery_level(pct_bat);
+
+		sprintf(str_v, "V :%7.5f", vbat);
 		sprintf(str_i, "I :%7.5f", current.val1 + current.val2 * 1e-6);
 		sprintf(str_p, "P :%7.4f", pressure.val1 + pressure.val2 * 1e-6);
 		sprintf(str_t, "T :%7.4f", temperature.val1 + temperature.val2 * 1e-6);

firmware/app/src/peripheral_gatt_write.c

@@ -11,6 +11,7 @@
 #include <zephyr/bluetooth/conn.h>
 #include <zephyr/bluetooth/gatt.h>
 #include <zephyr/bluetooth/hci.h>
+#include <zephyr/bluetooth/services/bas.h>
 
 extern int mtu_exchange(struct bt_conn *conn);
 extern int write_cmd(struct bt_conn *conn);
@@ -19,6 +20,9 @@ extern uint32_t last_write_rate;
 
 static const struct bt_data ad[] = {
 	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
+	BT_DATA_BYTES(BT_DATA_UUID16_ALL,
+				  BT_UUID_16_ENCODE(BT_UUID_BAS_VAL), // battery service
+				  ),
 	BT_DATA(BT_DATA_NAME_COMPLETE, CONFIG_BT_DEVICE_NAME, sizeof(CONFIG_BT_DEVICE_NAME) - 1), // -1 to strip \0
 };