Modbus - Accelerometer Bricklet 2.0

This is the description of the Modbus protocol for the Accelerometer Bricklet 2.0. General information and technical specifications for the Accelerometer Bricklet 2.0 are summarized in its hardware description.

API

A general description of the Modbus protocol structure can be found here.

Basic Functions

BrickletAccelerometerV2.get_acceleration
Function ID:
  • 1
Request:
  • empty payload
Response:
  • x – Type: int32, Unit: 1/10000 gₙ, Range: ?
  • y – Type: int32, Unit: 1/10000 gₙ, Range: ?
  • z – Type: int32, Unit: 1/10000 gₙ, Range: ?

Returns the acceleration in x, y and z direction. The values are given in gₙ/10000 (1gₙ = 9.80665m/s²). The range is configured with set_configuration.

If you want to get the acceleration periodically, it is recommended to use the CALLBACK_ACCELERATION callback and set the period with set_acceleration_callback_configuration.

BrickletAccelerometerV2.set_configuration
Function ID:
  • 2
Request:
  • data_rate – Type: uint8, Range: See meanings, Default: 7
  • full_scale – Type: uint8, Range: See meanings, Default: 0
Response:
  • no response

Configures the data rate and full scale range. Possible values are:

  • Data rate of 0.781Hz to 25600Hz.
  • Full scale range of ±2g up to ±8g.

Decreasing data rate or full scale range will also decrease the noise on the data.

The following meanings are defined for the elements of this function:

For data_rate:

  • 0 = 0.781Hz
  • 1 = 1.563Hz
  • 2 = 3.125Hz
  • 3 = 6.2512Hz
  • 4 = 12.5Hz
  • 5 = 25Hz
  • 6 = 50Hz
  • 7 = 100Hz
  • 8 = 200Hz
  • 9 = 400Hz
  • 10 = 800Hz
  • 11 = 1600Hz
  • 12 = 3200Hz
  • 13 = 6400Hz
  • 14 = 12800Hz
  • 15 = 25600Hz

For full_scale:

  • 0 = 2g
  • 1 = 4g
  • 2 = 8g
BrickletAccelerometerV2.get_configuration
Function ID:
  • 3
Request:
  • empty payload
Response:
  • data_rate – Type: uint8, Range: See meanings, Default: 7
  • full_scale – Type: uint8, Range: See meanings, Default: 0

Returns the configuration as set by set_configuration.

The following meanings are defined for the elements of this function:

For data_rate:

  • 0 = 0.781Hz
  • 1 = 1.563Hz
  • 2 = 3.125Hz
  • 3 = 6.2512Hz
  • 4 = 12.5Hz
  • 5 = 25Hz
  • 6 = 50Hz
  • 7 = 100Hz
  • 8 = 200Hz
  • 9 = 400Hz
  • 10 = 800Hz
  • 11 = 1600Hz
  • 12 = 3200Hz
  • 13 = 6400Hz
  • 14 = 12800Hz
  • 15 = 25600Hz

For full_scale:

  • 0 = 2g
  • 1 = 4g
  • 2 = 8g
BrickletAccelerometerV2.set_info_led_config
Function ID:
  • 6
Request:
  • config – Type: uint8, Range: See meanings, Default: 0
Response:
  • no response

Configures the info LED (marked as "Force" on the Bricklet) to be either turned off, turned on, or blink in heartbeat mode.

The following meanings are defined for the elements of this function:

For config:

  • 0 = Off
  • 1 = On
  • 2 = Show Heartbeat
BrickletAccelerometerV2.get_info_led_config
Function ID:
  • 7
Request:
  • empty payload
Response:
  • config – Type: uint8, Range: See meanings, Default: 0

Returns the LED configuration as set by set_info_led_config

The following meanings are defined for the elements of this function:

For config:

  • 0 = Off
  • 1 = On
  • 2 = Show Heartbeat
BrickletAccelerometerV2.set_continuous_acceleration_configuration
Function ID:
  • 9
Request:
  • enable_x – Type: bool, Default: false
  • enable_y – Type: bool, Default: false
  • enable_z – Type: bool, Default: false
  • resolution – Type: uint8, Range: See meanings, Default: 0
Response:
  • no response

For high throughput of acceleration data (> 1000Hz) you have to use the CALLBACK_CONTINUOUS_ACCELERATION_16_BIT or CALLBACK_CONTINUOUS_ACCELERATION_8_BIT callbacks.

You can enable the callback for each axis (x, y, z) individually and choose a resolution of 8 bit or 16 bit.

If at least one of the axis is enabled and the resolution is set to 8 bit, the CALLBACK_CONTINUOUS_ACCELERATION_8_BIT callback is activated. If at least one of the axis is enabled and the resolution is set to 16 bit, the CALLBACK_CONTINUOUS_ACCELERATION_16_BIT callback is activated.

The returned values are raw ADC data. If you want to put this data into a FFT to determine the occurrences of specific frequencies we recommend that you use the data as is. It has all of the ADC noise in it. This noise looks like pure noise at first glance, but it might still have some frequnecy information in it that can be utilized by the FFT.

Otherwise you have to use the following formulas that depend on the configured resolution (8/16 bit) and the full scale range (see set_configuration) to calculate the data in gₙ/10000 (same unit that is returned by get_acceleration):

  • 16 bit, full scale 2g: acceleration = value * 625 / 1024
  • 16 bit, full scale 4g: acceleration = value * 1250 / 1024
  • 16 bit, full scale 8g: acceleration = value * 2500 / 1024

If a resolution of 8 bit is used, only the 8 most significant bits will be transferred, so you can use the following formulas:

  • 8 bit, full scale 2g: acceleration = value * 256 * 625 / 1024
  • 8 bit, full scale 4g: acceleration = value * 256 * 1250 / 1024
  • 8 bit, full scale 8g: acceleration = value * 256 * 2500 / 1024

If no axis is enabled, both callbacks are disabled. If one of the continuous callbacks is enabled, the CALLBACK_ACCELERATION callback is disabled.

The maximum throughput depends on the exact configuration:

Number of axis enabled Throughput 8 bit Throughout 16 bit
1 25600Hz 25600Hz
2 25600Hz 15000Hz
3 20000Hz 10000Hz

The following meanings are defined for the elements of this function:

For resolution:

  • 0 = 8bit
  • 1 = 16bit
BrickletAccelerometerV2.get_continuous_acceleration_configuration
Function ID:
  • 10
Request:
  • empty payload
Response:
  • enable_x – Type: bool, Default: false
  • enable_y – Type: bool, Default: false
  • enable_z – Type: bool, Default: false
  • resolution – Type: uint8, Range: See meanings, Default: 0

Returns the continuous acceleration configuration as set by set_continuous_acceleration_configuration.

The following meanings are defined for the elements of this function:

For resolution:

  • 0 = 8bit
  • 1 = 16bit

Advanced Functions

BrickletAccelerometerV2.set_filter_configuration
Function ID:
  • 13
Request:
  • iir_bypass – Type: uint8, Range: See meanings, Default: 0
  • low_pass_filter – Type: uint8, Range: See meanings, Default: 0
Response:
  • no response

Configures IIR Bypass filter mode and low pass filter roll off corner frequency.

The filter can be applied or bypassed and the corner frequency can be half or a ninth of the output data rate.

Accelerometer filter

New in version 2.0.2 (Plugin).

The following meanings are defined for the elements of this function:

For iir_bypass:

  • 0 = Applied
  • 1 = Bypassed

For low_pass_filter:

  • 0 = Ninth
  • 1 = Half
BrickletAccelerometerV2.get_filter_configuration
Function ID:
  • 14
Request:
  • empty payload
Response:
  • iir_bypass – Type: uint8, Range: See meanings, Default: 0
  • low_pass_filter – Type: uint8, Range: See meanings, Default: 0

Returns the configuration as set by set_filter_configuration.

New in version 2.0.2 (Plugin).

The following meanings are defined for the elements of this function:

For iir_bypass:

  • 0 = Applied
  • 1 = Bypassed

For low_pass_filter:

  • 0 = Ninth
  • 1 = Half
BrickletAccelerometerV2.get_spitfp_error_count
Function ID:
  • 234
Request:
  • empty payload
Response:
  • error_count_ack_checksum – Type: uint32, Range: [0 to 232 - 1]
  • error_count_message_checksum – Type: uint32, Range: [0 to 232 - 1]
  • error_count_frame – Type: uint32, Range: [0 to 232 - 1]
  • error_count_overflow – Type: uint32, 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.

BrickletAccelerometerV2.set_bootloader_mode
Function ID:
  • 235
Request:
  • mode – Type: uint8, Range: See meanings
Response:
  • status – Type: uint8, Range: See meanings

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 meanings are defined for the elements of this function:

For mode:

  • 0 = Bootloader
  • 1 = Firmware
  • 2 = Bootloader Wait For Reboot
  • 3 = Firmware Wait For Reboot
  • 4 = Firmware Wait For Erase And Reboot

For status:

  • 0 = OK
  • 1 = Invalid Mode
  • 2 = No Change
  • 3 = Entry Function Not Present
  • 4 = Device Identifier Incorrect
  • 5 = CRC Mismatch
BrickletAccelerometerV2.get_bootloader_mode
Function ID:
  • 236
Request:
  • empty payload
Response:
  • mode – Type: uint8, Range: See meanings

Returns the current bootloader mode, see set_bootloader_mode.

The following meanings are defined for the elements of this function:

For mode:

  • 0 = Bootloader
  • 1 = Firmware
  • 2 = Bootloader Wait For Reboot
  • 3 = Firmware Wait For Reboot
  • 4 = Firmware Wait For Erase And Reboot
BrickletAccelerometerV2.set_write_firmware_pointer
Function ID:
  • 237
Request:
  • pointer – Type: uint32, Unit: 1 B, Range: [0 to 232 - 1]
Response:
  • no response

Sets the firmware pointer for 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.

BrickletAccelerometerV2.write_firmware
Function ID:
  • 238
Request:
  • data – Type: uint8[64], Range: [0 to 255]
Response:
  • status – Type: uint8, Range: [0 to 255]

Writes 64 Bytes of firmware at the position as written by 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.

BrickletAccelerometerV2.set_status_led_config
Function ID:
  • 239
Request:
  • config – Type: uint8, Range: See meanings, 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 meanings are defined for the elements of this function:

For config:

  • 0 = Off
  • 1 = On
  • 2 = Show Heartbeat
  • 3 = Show Status
BrickletAccelerometerV2.get_status_led_config
Function ID:
  • 240
Request:
  • empty payload
Response:
  • config – Type: uint8, Range: See meanings, Default: 3

Returns the configuration as set by set_status_led_config

The following meanings are defined for the elements of this function:

For config:

  • 0 = Off
  • 1 = On
  • 2 = Show Heartbeat
  • 3 = Show Status
BrickletAccelerometerV2.get_chip_temperature
Function ID:
  • 242
Request:
  • empty payload
Response:
  • temperature – Type: int16, 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.

BrickletAccelerometerV2.reset
Function ID:
  • 243
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!

BrickletAccelerometerV2.write_uid
Function ID:
  • 248
Request:
  • uid – Type: uint32, 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.

BrickletAccelerometerV2.read_uid
Function ID:
  • 249
Request:
  • empty payload
Response:
  • uid – Type: uint32, Range: [0 to 232 - 1]

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

BrickletAccelerometerV2.get_identity
Function ID:
  • 255
Request:
  • empty payload
Response:
  • uid – Type: char[8]
  • connected_uid – Type: char[8]
  • position – Type: char, Range: ['a' to 'h', 'i', 'z']
  • hardware_version – Type: uint8[3]
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • firmware_version – Type: uint8[3]
    • 0: major – Type: uint8, Range: [0 to 255]
    • 1: minor – Type: uint8, Range: [0 to 255]
    • 2: revision – Type: uint8, Range: [0 to 255]
  • device_identifier – Type: uint16, Range: [0 to 216 - 1]

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). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

The device identifier numbers can be found here

Callback Configuration Functions

BrickletAccelerometerV2.set_acceleration_callback_configuration
Function ID:
  • 4
Request:
  • period – Type: uint32, 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 CALLBACK_ACCELERATION 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.

If this callback is enabled, the CALLBACK_CONTINUOUS_ACCELERATION_16_BIT callback and CALLBACK_CONTINUOUS_ACCELERATION_8_BIT callback will automatically be disabled.

BrickletAccelerometerV2.get_acceleration_callback_configuration
Function ID:
  • 5
Request:
  • empty payload
Response:
  • period – Type: uint32, 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 set_acceleration_callback_configuration.

Callbacks

BrickletAccelerometerV2.CALLBACK_ACCELERATION
Function ID:
  • 8
Response:
  • x – Type: int32, Unit: 1/10000 gₙ, Range: ?
  • y – Type: int32, Unit: 1/10000 gₙ, Range: ?
  • z – Type: int32, Unit: 1/10000 gₙ, Range: ?

This callback is triggered periodically according to the configuration set by set_acceleration_callback_configuration.

The response values are the same as get_acceleration.

BrickletAccelerometerV2.CALLBACK_CONTINUOUS_ACCELERATION_16_BIT
Function ID:
  • 11
Response:
  • acceleration – Type: int16[30], Unit: ? gₙ, Range: ?

Returns 30 acceleration values with 16 bit resolution. The data rate can be configured with set_configuration and this callback can be enabled with set_continuous_acceleration_configuration.

The returned values are raw ADC data. If you want to put this data into a FFT to determine the occurrences of specific frequencies we recommend that you use the data as is. It has all of the ADC noise in it. This noise looks like pure noise at first glance, but it might still have some frequnecy information in it that can be utilized by the FFT.

Otherwise you have to use the following formulas that depend on the full scale range (see set_configuration) to calculate the data in gₙ/10000 (same unit that is returned by get_acceleration):

  • Full scale 2g: acceleration = value * 625 / 1024
  • Full scale 4g: acceleration = value * 1250 / 1024
  • Full scale 8g: acceleration = value * 2500 / 1024

The data is formated in the sequence "x, y, z, x, y, z, ..." depending on the enabled axis. Examples:

  • x, y, z enabled: "x, y, z, ..." 10x repeated
  • x, z enabled: "x, z, ..." 15x repeated
  • y enabled: "y, ..." 30x repeated
BrickletAccelerometerV2.CALLBACK_CONTINUOUS_ACCELERATION_8_BIT
Function ID:
  • 12
Response:
  • acceleration – Type: int8[60], Unit: ? gₙ, Range: ?

Returns 60 acceleration values with 8 bit resolution. The data rate can be configured with set_configuration and this callback can be enabled with set_continuous_acceleration_configuration.

The returned values are raw ADC data. If you want to put this data into a FFT to determine the occurrences of specific frequencies we recommend that you use the data as is. It has all of the ADC noise in it. This noise looks like pure noise at first glance, but it might still have some frequnecy information in it that can be utilized by the FFT.

Otherwise you have to use the following formulas that depend on the full scale range (see set_configuration) to calculate the data in gₙ/10000 (same unit that is returned by get_acceleration):

  • Full scale 2g: acceleration = value * 256 * 625 / 1024
  • Full scale 4g: acceleration = value * 256 * 1250 / 1024
  • Full scale 8g: acceleration = value * 256 * 2500 / 1024

The data is formated in the sequence "x, y, z, x, y, z, ..." depending on the enabled axis. Examples:

  • x, y, z enabled: "x, y, z, ..." 20x repeated
  • x, z enabled: "x, z, ..." 30x repeated
  • y enabled: "y, ..." 60x repeated