Software / API Bindings / MQTT / API Reference and Examples / Bricklets / Hall Effect Bricklet 2.0

MQTT - Hall Effect Bricklet 2.0¶

This is the description of the MQTT API bindings for the Hall Effect Bricklet 2.0. General information and technical specifications for the Hall Effect Bricklet 2.0 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).

Counter¶

Download (example-counter.txt)

# Change XYZ to the UID of your Hall Effect Bricklet 2.0

setup:
    # Get current count without counter reset
    subscribe to tinkerforge/response/hall_effect_v2_bricklet/XYZ/get_counter
    publish '{"reset_counter": false}' to tinkerforge/request/hall_effect_v2_bricklet/XYZ/get_counter

Magnetic Flux Density¶

Download (example-magnetic-flux-density.txt)

# Change XYZ to the UID of your Hall Effect Bricklet 2.0

setup:
    # Get current Magnetic Flux Density
    subscribe to tinkerforge/response/hall_effect_v2_bricklet/XYZ/get_magnetic_flux_density
    publish '' to tinkerforge/request/hall_effect_v2_bricklet/XYZ/get_magnetic_flux_density

Counter Callback¶

Download (example-counter-callback.txt)

# Change XYZ to the UID of your Hall Effect Bricklet 2.0

setup:
    # Configure counter with ±3000µT threshold and 10ms debounce
    publish '{"high_threshold": 3000, "low_threshold": -3000, "debounce": 10000}' to tinkerforge/request/hall_effect_v2_bricklet/XYZ/set_counter_config

    # Handle incoming counter callbacks
    subscribe to tinkerforge/callback/hall_effect_v2_bricklet/XYZ/counter
    publish '{"register": true}' to tinkerforge/register/hall_effect_v2_bricklet/XYZ/counter # Register counter callback

    # Set period for counter callback to 0.1s (100ms)
    publish '{"period": 100, "value_has_to_change": true}' to tinkerforge/request/hall_effect_v2_bricklet/XYZ/set_counter_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 member _ERROR. It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions¶

request/hall_effect_v2_bricklet/<UID>/get_magnetic_flux_density¶

Request:	empty payload
Response:	magnetic_flux_density – Type: int, Unit: 1 µT, Range: [-7000 to 7000]

Returns the magnetic flux density (magnetic induction).

If you want to get the value periodically, it is recommended to use the register/hall_effect_v2_bricklet/<UID>/magnetic_flux_density callback. You can set the callback configuration with request/hall_effect_v2_bricklet/<UID>/set_magnetic_flux_density_callback_configuration.

request/hall_effect_v2_bricklet/<UID>/get_counter¶

Request:	reset_counter – Type: bool
Response:	count – Type: int, Range: [0 to 2³² - 1]

Returns the current value of the counter.

You can configure the low/high thresholds and the debounce time with request/hall_effect_v2_bricklet/<UID>/set_counter_config.

If you set reset counter to true, the count is set back to 0 directly after it is read.

If you want to get the count periodically, it is recommended to use the register/hall_effect_v2_bricklet/<UID>/counter callback. You can set the callback configuration with request/hall_effect_v2_bricklet/<UID>/set_counter_callback_configuration.

request/hall_effect_v2_bricklet/<UID>/set_counter_config¶

Request:	high_threshold – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 2000 low_threshold – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: -2000 debounce – Type: int, Unit: 1 µs, Range: [0 to 1000000], Default: 100000
Response:	no response

Sets a high and a low threshold as well as a debounce time.

If the measured magnetic flux density goes above the high threshold or below the low threshold, the count of the counter is increased by 1.

The debounce time is the minimum time between two count increments.

request/hall_effect_v2_bricklet/<UID>/get_counter_config¶

Request:	empty payload
Response:	high_threshold – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 2000 low_threshold – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: -2000 debounce – Type: int, Unit: 1 µs, Range: [0 to 1000000], Default: 100000

Returns the counter config as set by request/hall_effect_v2_bricklet/<UID>/set_counter_config.

Advanced Functions¶

request/hall_effect_v2_bricklet/<UID>/get_spitfp_error_count¶

Request:	empty payload
Response:	error_count_ack_checksum – Type: int, Range: [0 to 2³² - 1] error_count_message_checksum – Type: int, Range: [0 to 2³² - 1] error_count_frame – Type: int, Range: [0 to 2³² - 1] error_count_overflow – Type: int, Range: [0 to 2³² - 1]

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/hall_effect_v2_bricklet/<UID>/set_status_led_config¶

Request:	config – Type: int, Range: See symbols, Default: 3
Response:	no response

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
"show_heartbeat" = 2
"show_status" = 3

request/hall_effect_v2_bricklet/<UID>/get_status_led_config¶

Request:	empty payload
Response:	config – Type: int, Range: See symbols, Default: 3

Returns the configuration as set by request/hall_effect_v2_bricklet/<UID>/set_status_led_config

The following symbols are available for this function:

For config:

"off" = 0
"on" = 1
"show_heartbeat" = 2
"show_status" = 3

request/hall_effect_v2_bricklet/<UID>/get_chip_temperature¶

Request:	empty payload
Response:	temperature – Type: int, Unit: 1 °C, Range: [-2¹⁵ to 2¹⁵ - 1]

Returns the temperature 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/hall_effect_v2_bricklet/<UID>/reset¶

Request:	empty payload
Response:	no response

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/hall_effect_v2_bricklet/<UID>/get_identity¶

Request:

empty payload

Response:

uid – Type: string, Length: up to 8
connected_uid – Type: string, Length: up to 8
position – Type: char, Range: ["a" to "h", "z"]
hardware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

firmware_version – Type: [int, ...], Length: 3

0: major – Type: int, Range: [0 to 255]
1: minor – Type: int, Range: [0 to 255]
2: revision – Type: int, Range: [0 to 255]

device_identifier – Type: int, Range: [0 to 2¹⁶ - 1]
_display_name – Type: 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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

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 Hall Effect 2.0's name in a human readable form.

Callback Configuration Functions¶

request/hall_effect_v2_bricklet/<UID>/set_magnetic_flux_density_callback_configuration¶

Request:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false option – Type: char, Range: See symbols, Default: "x" min – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 max – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0
Response:	no response

The period is the period with which the register/hall_effect_v2_bricklet/<UID>/magnetic_flux_density 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.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the register/hall_effect_v2_bricklet/<UID>/magnetic_flux_density callback.

The following options are possible:

Option	Description
'x'	Threshold is turned off
'o'	Threshold is triggered when the value is outside the min and max values
'i'	Threshold is triggered when the value is inside or equal to the min and max values
'<'	Threshold is triggered when the value is smaller than the min value (max is ignored)
'>'	Threshold is triggered when the value is greater than the min value (max is ignored)

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

The following symbols are available for this function:

For option:

"off" = "x"
"outside" = "o"
"inside" = "i"
"smaller" = "<"
"greater" = ">"

request/hall_effect_v2_bricklet/<UID>/get_magnetic_flux_density_callback_configuration¶

Request:	empty payload
Response:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false option – Type: char, Range: See symbols, Default: "x" min – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 max – Type: int, Unit: 1 µT, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0

Returns the callback configuration as set by request/hall_effect_v2_bricklet/<UID>/set_magnetic_flux_density_callback_configuration.

The following symbols are available for this function:

For option:

"off" = "x"
"outside" = "o"
"inside" = "i"
"smaller" = "<"
"greater" = ">"

request/hall_effect_v2_bricklet/<UID>/set_counter_callback_configuration¶

Request:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false
Response:	no response

The period is the period with which the register/hall_effect_v2_bricklet/<UID>/counter 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 at least one of the values has changed. If the values 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.

request/hall_effect_v2_bricklet/<UID>/get_counter_callback_configuration¶

Request:	empty payload
Response:	period – Type: int, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false

Returns the callback configuration as set by request/hall_effect_v2_bricklet/<UID>/set_counter_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/hall_effect_v2_bricklet/<UID>/magnetic_flux_density¶

Register Request:	register – Type: bool
Callback Response:	magnetic_flux_density – Type: int, Unit: 1 µT, Range: [-7000 to 7000]

A callback can be registered for this event by publishing to the .../register/hall_effect_v2_bricklet/<UID>/magnetic_flux_density[/<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/hall_effect_v2_bricklet/<UID>/magnetic_flux_density[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically according to the configuration set by request/hall_effect_v2_bricklet/<UID>/set_magnetic_flux_density_callback_configuration.

The callback payload is the same as request/hall_effect_v2_bricklet/<UID>/get_magnetic_flux_density.

register/hall_effect_v2_bricklet/<UID>/counter¶

Register Request:	register – Type: bool
Callback Response:	count – Type: int, Range: [0 to 2³² - 1]

A callback can be registered for this event by publishing to the .../register/hall_effect_v2_bricklet/<UID>/counter[/<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/hall_effect_v2_bricklet/<UID>/counter[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically according to the configuration set by request/hall_effect_v2_bricklet/<UID>/set_counter_callback_configuration.

The count is the same as you would get with request/hall_effect_v2_bricklet/<UID>/get_counter.

Internal Functions¶

Internal functions are used for maintenance tasks such as flashing a new firmware of changing the UID of a Bricklet. These task should be performed using Brick Viewer instead of using the internal functions directly.

request/hall_effect_v2_bricklet/<UID>/set_bootloader_mode¶

Request:	mode – Type: int, Range: See symbols
Response:	status – Type: int, Range: See 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
"bootloader_wait_for_reboot" = 2
"firmware_wait_for_reboot" = 3
"firmware_wait_for_erase_and_reboot" = 4

For status:

"ok" = 0
"invalid_mode" = 1
"no_change" = 2
"entry_function_not_present" = 3
"device_identifier_incorrect" = 4
"crc_mismatch" = 5

request/hall_effect_v2_bricklet/<UID>/get_bootloader_mode¶

Request:	empty payload
Response:	mode – Type: int, Range: See symbols

Returns the current bootloader mode, see request/hall_effect_v2_bricklet/<UID>/set_bootloader_mode.

The following symbols are available for this function:

For mode:

"bootloader" = 0
"firmware" = 1
"bootloader_wait_for_reboot" = 2
"firmware_wait_for_reboot" = 3
"firmware_wait_for_erase_and_reboot" = 4

request/hall_effect_v2_bricklet/<UID>/set_write_firmware_pointer¶

Request:	pointer – Type: int, Unit: 1 B, Range: [0 to 2³² - 1]
Response:	no response

Sets the firmware pointer for request/hall_effect_v2_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/hall_effect_v2_bricklet/<UID>/write_firmware¶

Request:	data – Type: [int, ...], Length: 64, Range: [0 to 255]
Response:	status – Type: int, Range: [0 to 255]

Writes 64 Bytes of firmware at the position as written by request/hall_effect_v2_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/hall_effect_v2_bricklet/<UID>/write_uid¶

Request:	uid – Type: int, Range: [0 to 2³² - 1]
Response:	no response

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/hall_effect_v2_bricklet/<UID>/read_uid¶

Request:	empty payload
Response:	uid – Type: int, Range: [0 to 2³² - 1]

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