TMCL™ Firmware Manual - Trinamic

PD-109-57 V2 TMCL Firmware Manual (V1.00/2010-FEB-18) 92
9.2 Stall detection
The TMCM-109 is offered with stallGuard. In this case the module is equipped with a TMC249 motor driver
chip, which features load measurement that can be used for stall detection. Stall detection means that the
motor will be stopped when the load gets too high. It is controlled by axis parameter #205. If this
parameter is set to a value between 1 and 7 the stall detection will be activated. Setting it to 0 means that
stall detection is turned off. A greater value means a higher threshold. This also depends on the motor and
on the velocity. There is no stall detection while the motor is being accelerated or decelerated.
Stall detection can also be used for finding the reference point. You can do this by using the following
TMCL code:
SAP 205, 0, 5 //Turn on Stall Detection (use other threshold if needed)
ROL 0, 500 //Let the motor run (or use ROR or other velocity)
Loop: GAP 3, 0
COMP 0
JC NE, Loop //Wait until the motor has stopped
SAP 1, 0, 0 //Set this position as the zero position
Do not use RFS in this case.
Mixed decay should be switched off when stallGuard is operational in order to get usable results.
9.3 Fixing microstep errors
Due to the zero crossing problem of the TMC249 stepper motor drivers, microstep errors may occur with
some motors as the minimum motor current that can be reached is slightly higher than zero (depending on
the inductivity, resistance and supply voltage of the motor).
This can be solved by setting the mixed decay threshold parameter (axis parameter number 203) to the value
-1. This switches on mixed decay permanently, in every part of the microstepping waveform. Now the
minimum reachable motor current is always near zero which gives better microstepping results.
A further optimization is possible by adapting the motor current shape. (For further information about TMCL-
IDE please refer to the TMCL reference and programming manual.)
Use SAP 203, , -1 to turn on this feature.
Copyright © 2010, TRINAMIC Motion Control GmbH & Co. KG