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Application Interfaces

Since the MSG gripper is based on STEPFOC drivers, which are based on Spectral Micro BLDC drivers, it inherits their control methods and functionality. This page describes only the commands needed for gripper operation. For the full command list, go here. The gripper is also based on Spectral Micro, so it includes a UART interface for control.

CAN ID bit layout for MSG gripper

Bits 10 - 7 of CAN ID represent the node ID. Node IDs range from 0 to 15, which means you can have a maximum of 16 different devices on one CAN bus.

Default node ID

The default node ID of the gripper is 0. To change it, check the Spectral Micro docs.

Bits 6 - 1 of the CAN ID represent the command ID. Command IDs range from 0 to 63.

Bit 0 represents the error bit. If STEPFOC has any active error, this bit is set to 1. This bit is always sent by the driver and is independent of command ID and data.

Node with smallest Node ID is strongest in CAN bus arbitration.

CAN commands

Respond_Gripper_data_pack

  • Command ID: 60
  • Direction: Gripper -> host
  • Python call: None, this command is sent only by driver
  • Length: 4 bytes
  • Type of frame: standard
Size (bytes) Variable (STEPFCO Lib python attribute) Type Details
0 gripper_position unsigned 8bit
1-2 gripper_current 16 bit signed
3(bit 0) gripper_activated bit (0/1) gripper activated (1) / deactivated (0)
3(bit 1) gripper_action_status bit (0/1) 1 is goto, 0 is idle or performing auto release or in calibration
3(bit 2 and 3) gripper_object_detection 2 bit 0 in motion, 1 object detected while closing, 2 object detected while opening, 3 at position
3(bit 4) gripper_temperature_error bit (0/1) gripper_temperature_error
3(bit 5) gripper_timeout_error bit (0/1) gripper_timeout_error
3(bit 6) gripper_estop_error bit (0/1) gripper_estop_error
3(bit 7) gripper_calibrated bit (0/1) gripper calibration status; calibrated (1) / not calibrated (0)

Send_gripper_data_pack

  • Command ID: 61
  • Direction: Host -> Gripper
  • Python API reference: Send_gripper_data_pack()
  • Type of frame: standard
  • Length: 5 bytes
Size (bytes) Variable Type Details
0 Position unsigned 8bit
1 Velocity unsigned 8bit
2-3 Current signed 16bit
4(bit 0) Gripper activate bit (0/1) 0 - deactivate the gripper, 1 - activate the gripper
4(bit 1) Gripper action status bit (0/1) 0 - idle , 1 - movement
4(bit 2) Gripper estop status bit (0/1) 0 - No estop, 1 - Estop pressed
4(bit 3) Gripper release direction bit (0/1) Not used

Driver will respond to this command with:
Respond_Gripper_data_pack

Alternatively, you can send an empty Send_gripper_data_pack command.

  • Command ID: 61
  • Direction: Host -> Gripper
  • Python API reference: Send_gripper_data_pack()
  • Type of frame: standard
  • Length: 0 bytes

Driver will respond to this command with:
Respond_Gripper_data_pack

Send_gripper_calibrate

  • Command ID: 62
  • Direction: Host -> Gripper
  • Python API reference: Send_gripper_calibrate()
  • Type of frame: standard
  • Length: 0 bytes

Driver will not respond to this command!

Send_CAN_ID

This command will set a new CAN ID for your motor driver.
The ID you send becomes the new motor ID.

  • Command ID: 11
  • Direction: Host -> Gripper
  • Python API reference: Send_CAN_ID()
  • Type of frame: standard
  • Length: 1 byte
Size (bytes) Variable Type
0 ID byte

Driver will not respond to this command!

Send_Save_config

  • Command ID: 13
  • Direction: Host -> Gripper
  • Python API reference: Send_Save_config()
  • Type of frame: standard
  • Length: 0 bytes

Driver will not respond to this command!

Send_Reset

  • Command ID: 14
  • Direction: Host -> Gripper
  • Python API reference: Send_Reset()
  • Type of frame: standard
  • Length: 0 bytes

Driver will not respond to this command!

Send_Clear_Error

  • Command ID: 1
  • Direction: Host -> Gripper
  • Python API reference: Send_Clear_Error()
  • Type of frame: standard
  • Length: 0 bytes

Driver will not respond to this command!

UART interface

For the full list of UART commands, check this link.

Gripper commands

Commands used in gripper mode. Procedure:

  • Gripper 1 (tells the motor controller to operate as a gripper)
  • Gripcal (calibrates the gripper)
  • Gripvel x (x is a value from 0 - 255; 0 is minimum speed, 255 is maximum speed)
  • Gripcur x (x is value from 0 - 1000 [mA])
  • Grippos x (x is a value from 0 - 255; 0 is fully open, 255 is fully closed)
Name Type Input Data type Description Response
Gripper Set/Get bool Set/get Am I a gripper Is this device gripper or not
Gripcal Action Start gripper calibration None
Grippos Set/Get uint8_t Set/get desired gripper setpoint position (from 0 to 255). Also sets gripper into GOTO mode and executes the command Gripper position value
Gripvel Set/Get uint8_t Set/get desired gripper velocity setpoint (from 0 to 255) Gripper velocity value setpoint
Gripcur Set/Get int Set/get desired gripper current in mA from 0 - 1000 (values below 150 can be unstable) Gripper current value setpoint; to get actual current value use #Iq
Gripact Set/Get bool Set/get gripper activation bit Is gripper activated or not
Gripstop Set/Get bool Set/get gripper Estop bit Gripper estop bit status
Gripinfo Action Print information about this gripper All information about gripper like: is it calibrated, status, endstop values...