MQTT - Energy Monitor Bricklet

This is the description of the MQTT 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 MQTT API bindings is part of their general description.

Examples

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

Simple

Download (example-simple.txt)

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# Change XYZ to the UID of your Energy Monitor Bricklet

setup:
    # Get current Energy Data
    subscribe to tinkerforge/response/energy_monitor_bricklet/XYZ/get_energy_data
    publish '' to tinkerforge/request/energy_monitor_bricklet/XYZ/get_energy_data

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Energy Monitor Bricklet

setup:
    # Handle incoming Energy Data callbacks
    subscribe to tinkerforge/callback/energy_monitor_bricklet/XYZ/energy_data
    publish '{"register": true}' to tinkerforge/register/energy_monitor_bricklet/XYZ/energy_data # Register energy_data callback
    
    # Set period for Energy Data callback to 1s (1000ms)
    publish '{"period": 1000, "value_has_to_change": false}' to tinkerforge/request/energy_monitor_bricklet/XYZ/set_energy_data_callback_configuration

API

All published payloads to and from the MQTT bindings are in JSON format.

If an error occures, the bindings publish a JSON object containing the error message as attribute "_ERROR". It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions

request/energy_monitor_bricklet/<UID>/get_energy_data
Response payload:
  • voltage -- int
  • current -- int
  • energy -- int
  • real_power -- int
  • apparent_power -- int
  • reactive_power -- int
  • power_factor -- int
  • frequency -- int

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.

request/energy_monitor_bricklet/<UID>/reset_energy

Sets the energy value (see request/energy_monitor_bricklet/<UID>/get_energy_data) back to 0Wh.

request/energy_monitor_bricklet/<UID>/get_waveform
Response payload:
  • waveform -- [int,... (x1536)]

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.

request/energy_monitor_bricklet/<UID>/get_transformer_status
Response payload:
  • voltage_transformer_connected -- bool
  • current_transformer_connected -- bool

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

request/energy_monitor_bricklet/<UID>/set_transformer_calibration
Request payload:
  • voltage_ratio -- int
  • current_ratio -- int
  • phase_shift -- int

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.

request/energy_monitor_bricklet/<UID>/get_transformer_calibration
Response payload:
  • voltage_ratio -- int
  • current_ratio -- int
  • phase_shift -- int

Returns the transformer calibration as set by request/energy_monitor_bricklet/<UID>/set_transformer_calibration.

request/energy_monitor_bricklet/<UID>/calibrate_offset

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

request/energy_monitor_bricklet/<UID>/get_spitfp_error_count
Response payload:
  • error_count_ack_checksum -- int
  • error_count_message_checksum -- int
  • error_count_frame -- int
  • error_count_overflow -- int

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.

request/energy_monitor_bricklet/<UID>/set_bootloader_mode
Request payload:
  • mode -- int (has symbols)
Response payload:
  • status -- int (has symbols)

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 symbols are available for this function:

for mode:

  • "Bootloader" = 0
  • "Firmware" = 1
  • "BootloaderWaitForReboot" = 2
  • "FirmwareWaitForReboot" = 3
  • "FirmwareWaitForEraseAndReboot" = 4

for status:

  • "OK" = 0
  • "InvalidMode" = 1
  • "NoChange" = 2
  • "EntryFunctionNotPresent" = 3
  • "DeviceIdentifierIncorrect" = 4
  • "CRCMismatch" = 5
request/energy_monitor_bricklet/<UID>/get_bootloader_mode
Response payload:
  • mode -- int (has symbols)

Returns the current bootloader mode, see request/energy_monitor_bricklet/<UID>/set_bootloader_mode.

The following symbols are available for this function:

for mode:

  • "Bootloader" = 0
  • "Firmware" = 1
  • "BootloaderWaitForReboot" = 2
  • "FirmwareWaitForReboot" = 3
  • "FirmwareWaitForEraseAndReboot" = 4
request/energy_monitor_bricklet/<UID>/set_write_firmware_pointer
Request payload:
  • pointer -- int

Sets the firmware pointer for request/energy_monitor_bricklet/<UID>/write_firmware. 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.

request/energy_monitor_bricklet/<UID>/write_firmware
Request payload:
  • data -- [int,... (x64)]
Response payload:
  • status -- int

Writes 64 Bytes of firmware at the position as written by request/energy_monitor_bricklet/<UID>/set_write_firmware_pointer 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.

request/energy_monitor_bricklet/<UID>/set_status_led_config
Request payload:
  • config -- int (has symbols)

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 symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowStatus" = 3
request/energy_monitor_bricklet/<UID>/get_status_led_config
Response payload:
  • config -- int (has symbols)

Returns the configuration as set by request/energy_monitor_bricklet/<UID>/set_status_led_config

The following symbols are available for this function:

for config:

  • "Off" = 0
  • "On" = 1
  • "ShowHeartbeat" = 2
  • "ShowStatus" = 3
request/energy_monitor_bricklet/<UID>/get_chip_temperature
Response payload:
  • temperature -- int

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.

request/energy_monitor_bricklet/<UID>/reset

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!

request/energy_monitor_bricklet/<UID>/write_uid
Request payload:
  • uid -- int

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.

request/energy_monitor_bricklet/<UID>/read_uid
Response payload:
  • uid -- int

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

request/energy_monitor_bricklet/<UID>/get_identity
Response payload:
  • uid -- string
  • connected_uid -- string
  • position -- char
  • hardware_version -- [int,int,int]
  • firmware_version -- [int,int,int]
  • device_identifier -- int (has symbols)
  • _display_name -- string

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. If symbolic output is not disabled, the device identifier is mapped to the corresponding name in the format used in topics.

The display name contains the Energy Monitor's name in a human readable form.

Callback Configuration Functions

request/energy_monitor_bricklet/<UID>/set_energy_data_callback_configuration
Request payload:
  • period -- int
  • value_has_to_change -- bool

The period in ms is the period with which the register/energy_monitor_bricklet/<UID>/energy_data 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).

request/energy_monitor_bricklet/<UID>/get_energy_data_callback_configuration
Response payload:
  • period -- int
  • value_has_to_change -- bool

Returns the callback configuration as set by request/energy_monitor_bricklet/<UID>/set_energy_data_callback_configuration.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding .../register/... topic and an optional suffix. This suffix 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.

register/energy_monitor_bricklet/<UID>/energy_data
Request payload:
  • register -- bool
Response payload:
  • voltage -- int
  • current -- int
  • energy -- int
  • real_power -- int
  • apparent_power -- int
  • reactive_power -- int
  • power_factor -- int
  • frequency -- int

A callback can be registered for this event by publishing to the .../register/energy_monitor_bricklet/<UID>/energy_data[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/energy_monitor_bricklet/<UID>/energy_data[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically according to the configuration set by request/energy_monitor_bricklet/<UID>/set_energy_data_callback_configuration.

The callback payload members are the same as request/energy_monitor_bricklet/<UID>/get_energy_data.