Datasheet

TMC2130 DATASHEET (Rev. 1.09 / 2017-MAY-15) 77
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18.4 Stall Detection in dcStep Mode
While dcStep is able to decelerate the motor upon overload, it cannot avoid a stall in every operation
situation. Once the motor is blocked, or it becomes decelerated below a motor dependent minimum
velocity where the motor operation cannot safely be detected any more, the motor may stall and
loose steps. In order to safely detect a step loss and avoid restarting of the motor, monitor the stall
output signal for stall detection. A stallGuard2 load value also is available during dcStep operation.
The range of values is limited to 0 to 255, in certain situations up to 511 will be read out. In order to
enable stallGuard, also set TCOOLTHRS corresponding to a velocity slightly above VDCMIN or up to
VMAX.
Stall detection in this mode may trigger falsely due to resonances, when flywheel loads are loosely
coupled to the motor axis.
Parameter
Description
Range
Comment
vhighfs
&
vhighchm
These chopper configuration flags in CHOPCONF
need to be set for dcStep operation. As soon as
VDCMIN becomes exceeded, the chopper becomes
switched to fullstepping.
0 / 1
set to 1 for dcStep
TOFF
dcStep often benefits from an increased off time
value in CHOPCONF. Settings >2 should be
preferred.
2… 15
Settings 8…15 do not make
any difference to setting 8
for dcStep operation.
VDCMIN
In case the external motion controller cannot
provide the lower dcStep velocity, this register
may be used to enforce start/restart of a blocked
motor. In dcStep operation, the motor operates at
minimum VDCMIN even when it is completely
blocked. Tune together with DC_TIME setting.
Activation of stealthChop also disables dcStep.
0… 2^22
0: Disable
Set to the low velocity
limit for dcStep operation
if desired.
DC_TIME
This setting controls the reference pulse width for
dcStep load measurement. It must be optimized
for robust operation with maximum motor torque.
A higher value allows higher torque and higher
velocity, a lower value allows operation down to
a lower velocity as set by VDCMIN.
Check best setting under nominal operation
conditions, and re-check under extreme operating
conditions (e.g. lowest operation supply voltage,
highest motor temperature, and highest supply
voltage, lowest motor temperature).
0… 1023
Lower limit for the setting
is: t
BLANK
(as defined by
TBL) in clock cycles + n
with n in the range 1 to
100 (for a typical motor)
DC_SG
This setting controls stall detection in dcStep
mode. A stall can be used as an error condition by
issuing a hard stop for the motor.
The stall detection is available as a pulse on
DIAG0 or DIAG1 output.
0… 255
Set slightly higher than
DC_TIME / 16