Datasheet

TMC2209 DATASHEET (Rev. 1.03 / 2019-JUN-26) 63
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13.4 Index Output
An active INDEX output signals that the sine curve of motor coil A is at its positive zero transition.
This correlates to the zero point of the microstep sequence. Usually, the cosine curve of coil B is at its
maximum at the same time. Thus, the index signal is active once within each electrical period, and
corresponds to a defined position of the motor within a sequence of four fullsteps. The INDEX output
this way allows the detection of a certain microstep pattern, and thus helps to detect a position with
more precision than a stop switch can do.
COIL A
COIL B
Current
Time
Time
Time
Current
INDEX
STEPS
0
Figure 13.3 Index signal at positive zero transition of the coil A sine curve
Hint
The index output allows precise detection of the microstep position within one electrical wave, i.e.
within a range of four fullsteps. With this, homing accuracy and reproducibility can be enhanced to
microstep accuracy, even when using an inexpensive home switch.