SIXpack 2 – Manual (V1.10 / January 29
th
, 2010)
23
The commands dataset itself contains a command byte and seven bytes to transfer parameters. The bytes have to
be transmitted even if they contain no data.
Figure 6.2: Command dataset
6.2.1
Hints for Programming
6.2.1.1
Strategy for Parameter Setting
The Pack can be parameterized for standard applications with a few commands since it is pre-set with default
values. However these default values should not substitute a thorough configuration of all parameters in a given
application. Normally the following parameters should be configured for your application:
6.2.1.2
Setting of Motor Current, refer to 5.6.1
Configure maximum current (s. CMD $10) and current control (s. CMD $11) as needed. The resulting current depends
on the maximum current defined by the DIP-switches. It is recommended to use motors with the same maximum
current for motors 1 & 2, 3 & 4 and 5 & 6, since their peak current setting (s. CMD $10) is linked together. The peak
current multiplies the maximum current defined by the DIP switches with value / 256. This provides a very exact
peak current setting. The minimum current (which provides proper microstepping) selected by current control is
19% (Index 6) for every parameter.
The current control (s. CMD $11) provides a coil current in percent of the peak current.
Example:
Connecting a 1A motor to channel 1 and a 600mA motor to channel 2
Motor 1 is specified by the manufacturer for 1A RMS current. The required peak current then is 1.4A in microstep
operation. The nearest DIP switch setting is 1.5A. Now, set the peak current setting to 1.4/1.5*255 = 238. For motor
2, peak current requirement is 600mA*1.4=840mA. We now can try with a DIP switch setting of 1.0A. Using the
setting for motor 1, This gives us a peak current of 1A*238/255=0.93A. This is too much, but now we have the
following possibilities: 1. Scale down the situation dependant setting. 2. Reduce DIP current setting to 800mA,
resulting in 0.74A peak, which is slightly lower than desired. Or 3., reduce motor peak current setting for motor 1
and 2. Be careful not to exceed the motor’s maximum specified current! It is easier to pair same motors at
neighboring channels.
6.2.1.3
Velocity Configuration (global)
Calculate
clkdiv
(s. CMD $12, SQPack-Tab “Velocity & Acceleration”) with the step frequency formula (s. begin of
chapter Instruction Set) so that the required maximum step velocity is achieved with
v
i
= 511 and small values
div
i
= 0 or 1.
6.2.1.4
Setting of starting Velocity, max. Velocity and max. Acceleration
These values (s. CMD $13 and $14) should be adapted to the motor type, mechanical load, and so on. As a
reference value
div
i
should be set so, that the maximum velocity
vmax
could be set between 256 and 511. This
way maximum resolution is obtainable. Then the acceleration
amax
can be configured. The velocity
vstart
should
not be set too low.
6.2.1.5
Setting of Motor Parameters and Reference Search Parameters
These settings describe the axis type, the reference search, and so on. For time saving purposes both, fast
reference search
FastRef
(s. CMD $15 P6, Bit1) should be activated and the maximum velocity for this reference
