Datasheet

TMC2130 DATASHEET (Rev. 1.09 / 2017-MAY-15) 75
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- DCO – Informs the motion controller when motor is not ready to take a new step (low level).
The motion controller shall react by delaying the next step until DCO becomes high.
The sequencer can buffer up to the effective number of microsteps per fullstep to allow
the motion controller to react to assertion of DCO. In case the motor is blocked this
wait situation can be terminated after a timeout by providing a long > 1024 clock STEP
input, or via the internal VDCMIN setting.
- DCIN – Commands the driver to wait with step execution and to disable DCO. This input can be
used for synchronization of multiple drivers operating with dcStep.
18.3.1 Using LOST_STEPS for dcStep Operation
This is the simplest possibility to integrate dcStep with a dedicated motion controller: the motion
controller enables dcStep using DCEN or the internal velocity threshold. The TMC2130 tries to follow
the steps. In case it needs to slow down the motor, it counts the difference between incoming steps
on the STEP signal and steps going to the motor. The motion controller can read out the difference
and compensate for the difference after the motion or on a cyclic basis. Figure 18.3 shows the
principle (simplified).
In case the motor driver needs to postpone steps due to detection of a mechanical overload in
dcStep, and the motion controller does not react to this by pausing the step generation, LOST_STEPS
becomes incremented or decremented (depending on the direction set by DIR) with each step which
is not taken. This way, the number of lost steps can be read out and executed later on or be
appended to the motion. As the driver needs to slow down the motor while the overload situation
persists, the application will benefit from a high microstepping resolution, because it allows more
seamless acceleration or deceleration in dcStep operation. In case the application is completely
blocked, VDCMIN sets a lower limit to the step execution. If the motor velocity falls below this limit,
however an unknown number of steps is lost and the motor position is not exactly known any more.
DCIN allows for step synchronization of two drivers: it stops the execution of steps if low and sets
DCO low.
+IMAX
-IMAX
0
STEP
DC_EN
DC_OUT
DCO signals that the driver is not ready for new steps. In this case, the controller does not react to this information.
Actual motor velocity
0
VDCMIN
dcStep enabled continuosly
VTARGET
Phase
Current
(one phase
shown)
Theoretical sine
wave
corresponding to
fullstep pattern
Steps from STEP input
skipped by the driver due
to light motor overload
LOSTSTEPS
0
2
4
8 12
16 20 22
24
LOSTSTEPS would count down if
motion direction is negative
Light motor overload reduces
effective motor velocity
Figure 18.3 Motor moving slower than STEP input due to light overload. LOSTSTEPS incremented