TMC428 ETC-unknow, TMC428 Datasheet - Page 38

• Manufacturer Part Number: TMC428
• Description: Intelligent Triple Stepper Motor Controller With Serial Peripheral Interfaces
• Manufacturer: ETC-unknow

TMC428 DATA SHEET (V. 1.00 / February 12, 2001)
The shape parameter s selects one of three functions f
two of them. The shape parameter s = 0 selects the function f
used for sine cosine micro stepping. With this, one gets the unit circle (r=1.0) by transformation to
cartesian coordinates {y = sin( ); x = cos( )} as outlined in Figure 16, a shape parameter s = +1.0 results
in a box, and a shape parameter s = -1.0 results in a rhomb. Other values except those, result in
something between box and circle respectively something between circle an rhomb.
The data values y(i) of the look-up table range from 0 to 63 and the argument i ranges also from 0 to 63.
In the following, natural angles (radians) ranging from (0 =
functions for superposition controlled by the shape parameter s are
All together, these three functions are combined to form the function
So, the shape parameter s selects the type of function and it also provides a continuous transition
between circle and box respectively circle and rhomb. To estimate, what function would be best for a
given type of stepper motor, one can try micro stepping based on different shape parameters s by
downloading different micro step tables on-the-fly into the TMC428 during motion of a stepper motor.
For calculation of data for the micro step look-up table of the TMC428, one has to replace
from 0 to
The amplitude of the shape function f
range of 0 to 63 for the on-chip RAM as described in the beginning of the micro stepping section.
Partial look-up table initialization option
A partially initialized micro step table may be sufficient, if all stepper motors– except those driven in full
step mode –are proposed to use the same micro step resolution constantly before a single micro step is
processed. But with a partial initialized micro step look-up table, the micro step resolution must not be
changed anyway. So, a partially initialized look-up table should be taken into account only, if it is a must
because of small memory of proposed used micro controller. Instead of partial initialization of the look-up
table of the TMC428, initialization the look-up table with a triangular function f
better choice.
Copyright © 2000, TRINAMIC Microchips GmbH
TRINAMIC
M I C R O C H I P S
f
(
)
f
f
f
box
circle
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/2 for the quarter period by
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for
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i
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