TMC2100 DATASHEET (Rev. 1.07 / 2017-MAY-15)
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11.3 microPlyer Step Interpolator and Stand Still Detection
For each active edge on STEP, microPlyer produces microsteps at 256x resolution, as shown in Figure
11.2. It interpolates the time in between of two step impulses at the step input based on the last
step interval. This way, from 2 microsteps (128 microstep to 256 microstep interpolation) up to 256
microsteps (full step input to 256 microsteps) are driven for a single step pulse.
The step rate for the interpolated 2 to 256 microsteps is determined by measuring the time interval of
the previous step period and dividing it into up to 256 equal parts. The maximum time between two
microsteps corresponds to 220 (roughly one million system clock cycles), for an even distribution of
256 microsteps. At 16MHz system clock frequency, this results in a minimum step input frequency of
16Hz for microPlyer operation. A lower step rate causes a standstill event to be detected. At that
frequency, microsteps occur at a rate of (system clock frequency)/216 ~ 256Hz. When a stand still is
detected, the driver automatically begins standby current reduction if selected by CFG6_ENN.
Attention
microPlyer only works perfectly with a stable STEP frequency.
STEP
Interpolated
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
microstep
Motor
angle
2^20 tCLK
STANDSTILL
(stst) active
Figure 11.2 microPlyer microstep interpolation with rising STEP frequency (Example: 16 to 256)
In Figure 11.2, the first STEP cycle is long enough to set the stst bit standstill. Detection of standstill
will enable the standby current reduction. This bit is cleared on the next STEP active edge. Then, the
external STEP frequency increases. After one cycle at the higher rate microPlyer adapts the
interpolated microstep rate to the higher frequency. During the last cycle at the slower rate,
microPlyer did not generate all 16 microsteps, so there is a small jump in motor angle between the
first and second cycles at the higher rate.
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