code: func (g *Driver) GetBatteryVoltage() (voltage float32, err error) {
  	val, err := g.readUint16(goPiGo3Address, GET_VOLTAGE_VCC)
  	return (float32(val) / 1000.0), err
  }
docs: // GetBatteryVoltage gets the battery voltage from the main battery pack (7v-12v).