batt_smbus: calculate current discharged

src/drivers/batt_smbus/batt_smbus.cpp

@@ -84,6 +84,7 @@
 #define BATT_SMBUS_ADDR				0x0B	///< I2C address
 #define BATT_SMBUS_TEMP				0x08	///< temperature register
 #define BATT_SMBUS_VOLTAGE			0x09	///< voltage register
+#define BATT_SMBUS_REMAINING_CAPACITY	0x0f	///< predicted remaining battery capacity as a percentage
 #define BATT_SMBUS_DESIGN_CAPACITY		0x18	///< design capacity register
 #define BATT_SMBUS_DESIGN_VOLTAGE		0x19	///< design voltage register
 #define BATT_SMBUS_SERIALNUM			0x1c	///< serial number register
@@ -179,6 +180,7 @@ private:
 	orb_advert_t		_batt_topic;	///< uORB battery topic
 	orb_id_t		_batt_orb_id;	///< uORB battery topic ID
 	uint64_t		_start_time;	///< system time we first attempt to communicate with battery
+	uint16_t		_batt_design_capacity;	///< battery's design capacity in mAh (0 means unknown)
 };
 
 namespace
@@ -197,7 +199,8 @@ BATT_SMBUS::BATT_SMBUS(int bus, uint16_t batt_smbus_addr) :
 	_reports(nullptr),
 	_batt_topic(-1),
 	_batt_orb_id(nullptr),
-	_start_time(0)
+	_start_time(0),
+	_batt_design_capacity(0)
 {
 	// work_cancel in the dtor will explode if we don't do this...
 	memset(&_work, 0, sizeof(_work));
@@ -263,7 +266,7 @@ BATT_SMBUS::test()
 
 		if (updated) {
 			if (orb_copy(ORB_ID(battery_status), sub, &status) == OK) {
-				warnx("V=%4.2f C=%4.2f", status.voltage_v, status.current_a);
+				warnx("V=%4.2f C=%4.2f DismAh=%4.2f", (float)status.voltage_v, (float)status.current_a, (float)status.discharged_mah);
 			}
 		}
 
@@ -371,6 +374,24 @@ BATT_SMBUS::cycle()
 			new_report.current_a = -(float)((int32_t)((uint32_t)buff[3] << 24 | (uint32_t)buff[2] << 16 | (uint32_t)buff[1] << 8 | (uint32_t)buff[0])) / 1000.0f;
 		}
 
+		// read battery design capacity
+		if (_batt_design_capacity == 0) {
+			usleep(1);
+			if (read_reg(BATT_SMBUS_DESIGN_CAPACITY, tmp) == OK) {
+				_batt_design_capacity = tmp;
+			}
+		}
+
+		// read remaining capacity
+		if (_batt_design_capacity > 0) {
+			usleep(1);
+			if (read_reg(BATT_SMBUS_REMAINING_CAPACITY, tmp) == OK) {
+				if (tmp < _batt_design_capacity) {
+					new_report.discharged_mah = _batt_design_capacity - tmp;
+				}
+			}
+		}
+
 		// publish to orb
 		if (_batt_topic != -1) {
 			orb_publish(_batt_orb_id, _batt_topic, &new_report);