Driver setup and first run¶

A gripper from the shop arrives with its driver configured: the stepper calibrated, gripper mode on, the thermistor on, the gains set, everything saved. A gripper you build has a bare STEPFOC driver that must be brought to the same state once, over its UART port. This page is that procedure; the commands are the driver's, and the STEPFOC documentation explains each in depth.

What you need¶

The driver mounted on the stepper with its encoder magnet, before the pinion is engaged in the racks: the motor calibration turns the motor several revolutions in both directions, which the racks cannot follow. Do this step with the stepper out of the gripper or with the pinion not yet fitted.
A 3.3 V USB-to-serial adapter on the driver's UART connector, a terminal at 256000 baud with CR+LF line endings, and 24 V on the driver's power connector. The serial terminal on the STEPFOC site shows the terminal setup.
The thermistor from the BOM, soldered to the driver's thermistor connector and fixed to the motor housing with thermal cement.

Static electricity damages the driver: touch earthed metal before you handle it, hold it by its edges, and connect and disconnect its cables with the supply off.

With Motor GUI¶

Motor GUI, connected over UART through the serial adapter, has a preset per stepper on its setup page: MSG 21.5 mm motor, MSG 40 mm motor and MSG 60 mm motor. A preset writes the stepper's resistance, inductance and 50 pole pairs, the current limit, the loop gains, gripper mode, the thermistor and the CAN ID, then saves; its CAN ID is 6, the PAR6 gripper's, so change it before applying for another robot. Apply it after the motor calibration of step 1: it does step 2 for you.

1. The motor calibration¶

Restore the defaults first, so that nothing from another motor or junk in the EEPROM goes into the calibration, then enter the stepper's parameters and calibrate:

Stepper	`#PP`	`#R`	`#L`
21.5 mm, 17HS08-1004S	50	3.7	0.0045
40 mm, 17HS16-2004S1	50	1.1	0.0026
60 mm, 17HS24-2104S	50	1.6	0.0030

#Default
#PP 50
#R 1.1
#L 0.0026
#Cal

The motor turns, the driver prints each step and ends with Calibration success!. The whole routine and its messages are in Calibration on the STEPFOC site. #Default also resets the serial number the driver reports; note what #SERNUM prints before you start if you need it.

Check

The terminal ends with Calibration success!, and #Info prints Calibrated, Number of pole pairs: 50 and the resistance and inductance you entered. If it ends with Calibration failed!, the STEPFOC page Calibration explains each message.

2. The gripper settings¶

#Gripper 1
#Term 1
#Tlim 75
#Kpiq 1.4047
#Kiiq 0.1149
#CANID 0
#Save

Command	What it does
`#Gripper 1`	gripper mode: the driver runs the gripper state machine and answers the gripper messages
`#Term 1`, `#Tlim 75`	the thermistor on, the temperature limit at 75 °C. Without it the motor can burn out under a long grip
`#Kpiq 1.4047`, `#Kiiq 0.1149`	the current loop gains of Motor GUI's gripper presets, the same for the three steppers; the gains the calibration computes for the stepper are sharper than a gripper needs
`#CANID 0`	the node ID on the robot's bus; 0 to 13, see Over CAN
`#Save`	nothing above survives a power cycle until it is saved

Check

After a power cycle, #Info prints CAN ID is: 0 and Gripper: 1, and #Gripinfo prints I am a gripper. If not, the settings were not saved: enter them again and end with #Save.

3. Assemble and calibrate the gripper¶

Fit the pinion and assemble the gripper, power it up, and run the gripper calibration (#Gripcal, or Motor GUI's Calibrate): the jaws open fully and close fully. Then a first move at a low current, as in Calibrate, activate, move. #Gripinfo prints the gripper's state, including the end stops the calibration found.

Check

The jaws opened fully and closed fully, #Gripinfo prints Gripper calibrated is: 1, and a move at a low current goes to its position. If the calibration gives up after 24 s: Calibration.

Current limit¶

The gripper's moves use the current limit of each command, not the driver's #Ilim. Keep the commanded current at or below the stepper's maximum current (Force and speed); the firmware does not clamp it.

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