ADI Trinamic Blog

Want to get rid of the Limit Switches? Homing using the Encoder Deviation

Limit switches require a lot of wiring, and are subject to wearout. With sensOstep PANdrives or modules using an external encoder the homing you can implement the homing with the following TMCL routine.

        VECT 21, DeviationIrq  //Define Interrupt on Encoder Deviation
        EI 21                  //Activate Interrupt
        EI 255
        
        SAP 212, 0, 5000       //max. Encoder-deviation
        ROR 0, 1000            //Start Motor
        
Loop:                          //Empty Main Loop
        JA Loop
        
DeviationIrq:                 //Interrupt Service Routine Motor is already haltet then
        SAP 0, 0, 0           //Set Position to 0 (homing)
        SAP 1, 0, 0
        SAP 209, 0, 0
        RETI

Drive the motor with a low current towards a mechanical reference position. As soon as it contacts the reference position, it is stopped. The encoder deviation will go up and trigger an interrupt.

As soon as the drives are stopped the interrupt service routine resets the position counter to zero.

Tested with a PD-1140 with integrated sensOstep Encoder

Categories: Code Snippet, Tutorial

Tags: Encoder, Homing, PANdrive, TMCL

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