Modbus - Load Cell Bricklet 2.0

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

API

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

Basic Functions

BrickletLoadCellV2.get_weight
Function ID:

1

Request:

empty payload

Response:
  • weight -- int32

Returns the currently measured weight in grams.

If you want to get the value periodically, it is recommended to use the CALLBACK_WEIGHT callback. You can set the callback configuration with set_weight_callback_configuration.

BrickletLoadCellV2.set_info_led_config
Function ID:

7

Request:
  • config -- uint8
Response:

no response

Configures the info LED to be either turned off, turned on, or blink in heartbeat mode.

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

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
BrickletLoadCellV2.get_info_led_config
Function ID:

8

Request:

empty payload

Response:
  • config -- uint8

Returns the LED configuration as set by set_info_led_config

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

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
BrickletLoadCellV2.tare
Function ID:10
Request:empty payload
Response:no response

Sets the currently measured weight as tare weight.

Advanced Functions

BrickletLoadCellV2.set_moving_average
Function ID:

5

Request:
  • average -- uint16
Response:

no response

Sets the length of a moving averaging for the weight value.

Setting the length to 1 will turn the averaging off. With less averaging, there is more noise on the data.

The range for the averaging is 1-100.

The default value is 4.

BrickletLoadCellV2.get_moving_average
Function ID:

6

Request:

empty payload

Response:
  • average -- uint16

Returns the length moving average as set by set_moving_average.

BrickletLoadCellV2.calibrate
Function ID:

9

Request:
  • weight -- uint32
Response:

no response

To calibrate your Load Cell Bricklet 2.0 you have to

  • empty the scale and call this function with 0 and
  • add a known weight to the scale and call this function with the weight in grams.

The calibration is saved in the flash of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for calibration, you don't need to call this function in your source code.

BrickletLoadCellV2.set_configuration
Function ID:

11

Request:
  • rate -- uint8
  • gain -- uint8
Response:

no response

The measurement rate and gain are configurable.

The rate can be either 10Hz or 80Hz. A faster rate will produce more noise. It is additionally possible to add a moving average (see set_moving_average) to the measurements.

The gain can be 128x, 64x or 32x. It represents a measurement range of ±20mV, ±40mV and ±80mV respectively. The Load Cell Bricklet uses an excitation voltage of 5V and most load cells use an output of 2mV/V. That means the voltage range is ±15mV for most load cells (i.e. gain of 128x is best). If you don't know what all of this means you should keep it at 128x, it will most likely be correct.

The default rate is 10Hz and the default gain is 128x.

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

  • 0: 10hz, for rate
  • 1: 80hz, for rate
  • 0: 128x, for gain
  • 1: 64x, for gain
  • 2: 32x, for gain
BrickletLoadCellV2.get_configuration
Function ID:

12

Request:

empty payload

Response:
  • rate -- uint8
  • gain -- uint8

Returns the configuration as set by set_configuration.

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

  • 0: 10hz, for rate
  • 1: 80hz, for rate
  • 0: 128x, for gain
  • 1: 64x, for gain
  • 2: 32x, for gain
BrickletLoadCellV2.get_spitfp_error_count
Function ID:

234

Request:

empty payload

Response:
  • error_count_ack_checksum -- uint32
  • error_count_message_checksum -- uint32
  • error_count_frame -- uint32
  • error_count_overflow -- uint32

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.

BrickletLoadCellV2.set_bootloader_mode
Function ID:

235

Request:
  • mode -- uint8
Response:
  • status -- uint8

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 parameters of this function:

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
  • 0: ok, for status
  • 1: invalid mode, for status
  • 2: no change, for status
  • 3: entry function not present, for status
  • 4: device identifier incorrect, for status
  • 5: crc mismatch, for status
BrickletLoadCellV2.get_bootloader_mode
Function ID:

236

Request:

empty payload

Response:
  • mode -- uint8

Returns the current bootloader mode, see set_bootloader_mode.

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

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
BrickletLoadCellV2.set_write_firmware_pointer
Function ID:

237

Request:
  • pointer -- uint32
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.

BrickletLoadCellV2.write_firmware
Function ID:

238

Request:
  • data -- uint8[64]
Response:
  • status -- uint8

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.

BrickletLoadCellV2.set_status_led_config
Function ID:

239

Request:
  • config -- uint8
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 parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletLoadCellV2.get_status_led_config
Function ID:

240

Request:

empty payload

Response:
  • config -- uint8

Returns the configuration as set by set_status_led_config

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

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletLoadCellV2.get_chip_temperature
Function ID:

242

Request:

empty payload

Response:
  • temperature -- int16

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.

BrickletLoadCellV2.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!

BrickletLoadCellV2.write_uid
Function ID:

248

Request:
  • uid -- uint32
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.

BrickletLoadCellV2.read_uid
Function ID:

249

Request:

empty payload

Response:
  • uid -- uint32

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

BrickletLoadCellV2.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

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

Callback Configuration Functions

BrickletLoadCellV2.set_weight_callback_configuration
Function ID:

2

Request:
  • period -- uint32
  • value_has_to_change -- bool
  • option -- char
  • min -- int32
  • max -- int32
Response:

no response

The period in ms is the period with which the CALLBACK_WEIGHT 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 CALLBACK_WEIGHT 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 default value is (0, false, 'x', 0, 0).

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

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletLoadCellV2.get_weight_callback_configuration
Function ID:

3

Request:

empty payload

Response:
  • period -- uint32
  • value_has_to_change -- bool
  • option -- char
  • min -- int32
  • max -- int32

Returns the callback configuration as set by set_weight_callback_configuration.

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

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option

Callbacks

BrickletLoadCellV2.CALLBACK_WEIGHT
Function ID:

4

Response:
  • weight -- int32

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

The response value is the same as get_weight.