Go - Energy Monitor Bricklet

This is the description of the Go API bindings for the Energy Monitor Bricklet. General information and technical specifications for the Energy Monitor Bricklet are summarized in its hardware description.

An installation guide for the Go API bindings is part of their general description. Additional documentation can be found on godoc.org.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example_simple.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/energy_monitor_bricklet"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Energy Monitor Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    em, _ := energy_monitor_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    // Get current Energy Data.
    voltage, current, energy, realPower, apparentPower, reactivePower, powerFactor, frequency, _ := em.GetEnergyData()

    fmt.Printf("Voltage: %f V\n", float64(voltage)/100.0)
    fmt.Printf("Current: %f A\n", float64(current)/100.0)
    fmt.Printf("Energy: %f Wh\n", float64(energy)/100.0)
    fmt.Printf("Real Power: %f h\n", float64(realPower)/100.0)
    fmt.Printf("Apparent Power: %f VA\n", float64(apparentPower)/100.0)
    fmt.Printf("Reactive Power: %f VAR\n", float64(reactivePower)/100.0)
    fmt.Printf("Power Factor: %f\n", float64(powerFactor)/1000.0)
    fmt.Printf("Frequency: %f Hz\n", float64(frequency)/100.0)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

Callback

Download (example_callback.go)

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package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/energy_monitor_bricklet"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Energy Monitor Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    em, _ := energy_monitor_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    em.RegisterEnergyDataCallback(func(voltage int32, current int32, energy int32, realPower int32, apparentPower int32, reactivePower int32, powerFactor uint16, frequency uint16) {
        fmt.Printf("Voltage: %f V\n", float64(voltage)/100.0)
        fmt.Printf("Current: %f A\n", float64(current)/100.0)
        fmt.Printf("Energy: %f Wh\n", float64(energy)/100.0)
        fmt.Printf("Real Power: %f h\n", float64(realPower)/100.0)
        fmt.Printf("Apparent Power: %f VA\n", float64(apparentPower)/100.0)
        fmt.Printf("Reactive Power: %f VAR\n", float64(reactivePower)/100.0)
        fmt.Printf("Power Factor: %f\n", float64(powerFactor)/1000.0)
        fmt.Printf("Frequency: %f Hz\n", float64(frequency)/100.0)
        fmt.Println()
    })

    // Set period for Energy Data callback to 1s (1000ms).
    em.SetEnergyDataCallbackConfiguration(1000, false)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

API

The Energy Monitor Bricklet API is defined in the package github.com/Tinkerforge/go-api-bindings/energy_monitor_bricklet

Nearly every function of the Go bindings can return an DeviceError, implementing the error interface. The error can have one of the following values:

  • DeviceErrorSuccess = 0
  • DeviceErrorInvalidParameter = 1
  • DeviceErrorFunctionNotSupported = 2
  • DeviceErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func energy_monitor_bricklet.New(uid string, ipcon *IPConnection) (device EnergyMonitorBricklet, err error)

Creates a new EnergyMonitorBricklet object with the unique device ID uid and adds it to the IPConnection ipcon:

device, err := energy_monitor_bricklet.New("YOUR_DEVICE_UID", &ipcon)

This device object can be used after the IPConnection has been connected (see examples above).

func (*EnergyMonitorBricklet) GetEnergyData() (voltage int32, current int32, energy int32, realPower int32, apparentPower int32, reactivePower int32, powerFactor uint16, frequency uint16, err error)

Returns all of the measurements that are done by the Energy Monitor Bricklet.

  • Voltage (V): Voltage RMS with a resolution of 10mV (example: 230.05V = 23005)
  • Current (A): Current RMS with a resolution of 10mA (example: 1.42A = 142)
  • Energy (Wh): Energy (integrated over time) with a resolution of 10mWh (example: 1.1kWh = 110000)
  • Real Power (W): Real Power with a resolution of 10mW (example: 1234.56W = 123456)
  • Apparent Power (VA): Apparent Power with a resolution of 10mVA (example: 1234.56VA = 123456)
  • Reactive Power (VAR): Reactive Power with a resolution of 10mVAR (example: 1234.56VAR = 123456)
  • Power Factor: Power Factor with a resolution of 1/1000 (example: PF 0.995 = 995)
  • Frequency (Hz): AC Frequency of the mains voltage with a resolution of 1/100 Hz (example: 50Hz = 5000)

The frequency is recalculated every 6 seconds.

All other values are integrated over 10 zero-crossings of the voltage sine wave. With a standard AC mains voltage frequency of 50Hz this results in a 5 measurements per second (or an integration time of 200ms per measurement).

If no voltage transformer is connected, the Bricklet will use the current waveform to calculate the frequency and it will use an integration time of 10 zero-crossings of the current waveform.

func (*EnergyMonitorBricklet) ResetEnergy() (err error)

Sets the energy value (see GetEnergyData()) back to 0Wh.

func (*EnergyMonitorBricklet) GetWaveform() (waveform []int16, err error)

Returns a snapshot of the voltage and current waveform. The values in the returned array alternate between voltage and current. The data from one getter call contains 768 data points for voltage and current, which correspond to about 3 full sine waves.

The voltage is given with a resolution of 100mV and the current is given with a resolution of 10mA.

This data is meant to be used for a non-realtime graphical representation of the voltage and current waveforms.

func (*EnergyMonitorBricklet) GetTransformerStatus() (voltageTransformerConnected bool, currentTransformerConnected bool, err error)

Returns true if a voltage/current transformer is connected to the Bricklet.

func (*EnergyMonitorBricklet) SetTransformerCalibration(voltageRatio uint16, currentRatio uint16, phaseShift int16) (err error)

Sets the transformer ratio for the voltage and current transformer in 1/100 form.

Example: If your mains voltage is 230V, you use 9V voltage transformer and a 1V:30A current clamp your voltage ratio is 230/9 = 25.56 and your current ratio is 30/1 = 30.

In this case you have to set the values 2556 and 3000 for voltage ratio and current ratio.

The calibration is saved in non-volatile memory, you only have to set it once.

By default the voltage ratio is set to 1923 and the current ratio is set to 3000.

Set the phase shift to 0. It is for future use and currently not supported by the Bricklet.

func (*EnergyMonitorBricklet) GetTransformerCalibration() (voltageRatio uint16, currentRatio uint16, phaseShift int16, err error)

Returns the transformer calibration as set by SetTransformerCalibration().

func (*EnergyMonitorBricklet) CalibrateOffset() (err error)

Calling this function will start an offset calibration. The offset calibration will integrate the voltage and current waveform over a longer time period to find the 0 transition point in the sine wave.

The Bricklet comes with a factory-calibrated offset value, you should not have to call this function.

If you want to re-calibrate the offset we recommend that you connect a load that has a smooth sinusoidal voltage and current waveform. Alternatively you can also short both inputs.

The calibration is saved in non-volatile memory, you only have to set it once.

Advanced Functions

func (*EnergyMonitorBricklet) GetAPIVersion() (apiVersion [3]uint8, err error)

Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

func (*EnergyMonitorBricklet) GetResponseExpected(functionId Function) (responseExpected bool, err error)

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by SetResponseExpected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

  • energy_monitor_bricklet.FunctionResetEnergy = 2
  • energy_monitor_bricklet.FunctionSetTransformerCalibration = 5
  • energy_monitor_bricklet.FunctionCalibrateOffset = 7
  • energy_monitor_bricklet.FunctionSetEnergyDataCallbackConfiguration = 8
  • energy_monitor_bricklet.FunctionSetWriteFirmwarePointer = 237
  • energy_monitor_bricklet.FunctionSetStatusLEDConfig = 239
  • energy_monitor_bricklet.FunctionReset = 243
  • energy_monitor_bricklet.FunctionWriteUID = 248
func (*EnergyMonitorBricklet) SetResponseExpected(functionId Function, responseExpected bool) (err error)

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

  • energy_monitor_bricklet.FunctionResetEnergy = 2
  • energy_monitor_bricklet.FunctionSetTransformerCalibration = 5
  • energy_monitor_bricklet.FunctionCalibrateOffset = 7
  • energy_monitor_bricklet.FunctionSetEnergyDataCallbackConfiguration = 8
  • energy_monitor_bricklet.FunctionSetWriteFirmwarePointer = 237
  • energy_monitor_bricklet.FunctionSetStatusLEDConfig = 239
  • energy_monitor_bricklet.FunctionReset = 243
  • energy_monitor_bricklet.FunctionWriteUID = 248
func (*EnergyMonitorBricklet) SetResponseExpectedAll(responseExpected bool) (err error)

Changes the response expected flag for all setter and callback configuration functions of this device at once.

func (*EnergyMonitorBricklet) GetSPITFPErrorCount() (errorCountAckChecksum uint32, errorCountMessageChecksum uint32, errorCountFrame uint32, errorCountOverflow uint32, err error)

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

func (*EnergyMonitorBricklet) SetBootloaderMode(mode BootloaderMode) (status BootloaderStatus, err error)

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following constants are available for this function:

  • energy_monitor_bricklet.BootloaderModeBootloader = 0
  • energy_monitor_bricklet.BootloaderModeFirmware = 1
  • energy_monitor_bricklet.BootloaderModeBootloaderWaitForReboot = 2
  • energy_monitor_bricklet.BootloaderModeFirmwareWaitForReboot = 3
  • energy_monitor_bricklet.BootloaderModeFirmwareWaitForEraseAndReboot = 4
  • energy_monitor_bricklet.BootloaderStatusOK = 0
  • energy_monitor_bricklet.BootloaderStatusInvalidMode = 1
  • energy_monitor_bricklet.BootloaderStatusNoChange = 2
  • energy_monitor_bricklet.BootloaderStatusEntryFunctionNotPresent = 3
  • energy_monitor_bricklet.BootloaderStatusDeviceIdentifierIncorrect = 4
  • energy_monitor_bricklet.BootloaderStatusCRCMismatch = 5
func (*EnergyMonitorBricklet) GetBootloaderMode() (mode BootloaderMode, err error)

Returns the current bootloader mode, see SetBootloaderMode().

The following constants are available for this function:

  • energy_monitor_bricklet.BootloaderModeBootloader = 0
  • energy_monitor_bricklet.BootloaderModeFirmware = 1
  • energy_monitor_bricklet.BootloaderModeBootloaderWaitForReboot = 2
  • energy_monitor_bricklet.BootloaderModeFirmwareWaitForReboot = 3
  • energy_monitor_bricklet.BootloaderModeFirmwareWaitForEraseAndReboot = 4
func (*EnergyMonitorBricklet) SetWriteFirmwarePointer(pointer uint32) (err error)

Sets the firmware pointer for WriteFirmware(). The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

func (*EnergyMonitorBricklet) WriteFirmware(data [64]uint8) (status uint8, err error)

Writes 64 Bytes of firmware at the position as written by SetWriteFirmwarePointer() before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

func (*EnergyMonitorBricklet) SetStatusLEDConfig(config StatusLEDConfig) (err error)

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following constants are available for this function:

  • energy_monitor_bricklet.StatusLEDConfigOff = 0
  • energy_monitor_bricklet.StatusLEDConfigOn = 1
  • energy_monitor_bricklet.StatusLEDConfigShowHeartbeat = 2
  • energy_monitor_bricklet.StatusLEDConfigShowStatus = 3
func (*EnergyMonitorBricklet) GetStatusLEDConfig() (config StatusLEDConfig, err error)

Returns the configuration as set by SetStatusLEDConfig()

The following constants are available for this function:

  • energy_monitor_bricklet.StatusLEDConfigOff = 0
  • energy_monitor_bricklet.StatusLEDConfigOn = 1
  • energy_monitor_bricklet.StatusLEDConfigShowHeartbeat = 2
  • energy_monitor_bricklet.StatusLEDConfigShowStatus = 3
func (*EnergyMonitorBricklet) GetChipTemperature() (temperature int16, err error)

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

func (*EnergyMonitorBricklet) Reset() (err error)

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

func (*EnergyMonitorBricklet) WriteUID(uid uint32) (err error)

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

func (*EnergyMonitorBricklet) ReadUID() (uid uint32, err error)

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

func (*EnergyMonitorBricklet) GetIdentity() (uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

func (*EnergyMonitorBricklet) SetEnergyDataCallbackConfiguration(period uint32, valueHasToChange bool) (err error)

The period in ms is the period with which the RegisterEnergyDataCallback callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

The default value is (0, false).

func (*EnergyMonitorBricklet) GetEnergyDataCallbackConfiguration() (period uint32, valueHasToChange bool, err error)

Returns the callback configuration as set by SetEnergyDataCallbackConfiguration().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding Register*Callback function, which returns a unique callback ID. This ID can be used to deregister the callback later.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

func (*EnergyMonitorBricklet) RegisterEnergyDataCallback(func(voltage int32, current int32, energy int32, realPower int32, apparentPower int32, reactivePower int32, powerFactor uint16, frequency uint16)) (registrationId uint64)

A callback can be registered for this event with the RegisterEnergyDataCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterEnergyDataCallback(registrationId uint64) function.

This callback is triggered periodically according to the configuration set by SetEnergyDataCallbackConfiguration().

The callback parameters are the same as GetEnergyData().

Constants

energy_monitor_bricklet.DeviceIdentifier

This constant is used to identify a Energy Monitor Bricklet.

The GetIdentity() function and the (*IPConnection) RegisterEnumerateCallback callback of the IPConnection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

energy_monitor_bricklet.DeviceDisplayName

This constant represents the human readable name of a Energy Monitor Bricklet.