To set the microstepping: start with the suggested PWM[] values ranging from 100 on down. Start with MsDelayX = 1, and MsPause = 0 if on a slower machine, and MsDelayX = 6 if on a faster machine. Adjust MsDelayX such that PWMRepsTick displayed (turn on tracking for a few seconds) is 20 to 40. People have reported mixed success with slow machines and PWMRepsTick values as low as 7. Values as high as 50 to 100 will also work. Find the MsDelayX value that results in smoothest motor rotation, adjusting MsPause to higher values possibly to 500 or more, to reduce voltage and current draw, and to smooth the motor rotation.

Here's how the microstepping is laid out:

To reverse motor direction, swap motor leads #1 and #3, or alternatively, #2 and #4. Finally, you can swap motor directions in the config.dat file.

**Adjusting the microsteps:**

The program now handles microstepping up to 40 microsteps per fullstep. The following was written with 10 microsteps per fullstep in mind.

For 10 microsteps per fullstep, the windings are combined as
follows:

;rotor centered on winding

PWM[0] 100

PWM[1] 100

PWM[2] 100

PWM[3] 100

PWM[4] 100

;rotor between
windings

PWM[5] 100

PWM[6] 85

PWM[7] 70

PWM[8] 55

PWM[9] 35

For 20 microsteps per fullstep, the windings are combined as
follows:

;rotor centered on winding

PWM[0] 100

PWM[1] 100

PWM[2] 100

PWM[3] 100

PWM[4] 100

PWM[5] 100

PWM[6]
100

PWM[7] 100

PWM[8] 100

PWM[9] 100

;rotor between
windings

PWM[10] 100

PWM[11] 94

PWM[12] 86

PWM[13] 77

PWM[14] 69

PWM[15] 62

PWM[16] 54

PWM[17] 46

PWM[18]
37

PWM[19] 27

(this written with 10 microsteps per fullstep in mind)

Set
TestString to Track in the config.dat file, and choose 1 microstep
per second. Put a piece of masking tape on the motor shaft and watch
it carefully for even spacing of the microsteps. If the step is too
far apart, bring the voltages closer together. For instance, if the
spacing between microstep #0 and #1 is too far, then lower PWM[9], if
the motor hardly seems to move between #0 and #1, increase PWM[9].
Again, if the spacing between #3 and #4 is too large, then increase
#3, or decrease #4, or a combination of the two. You can change
the PWM[] values on the fly. When you get them the way you
wish, copy the values to the config.dat file.

Here is a contributed method: "There is a way that I used to
find the proper PWM numbers for the drive that can interest you:

I
started first with approximate numbers in the software.

I mounted
a 7.96" plastic rod on the shaft to get a 50"
circumference or 0.025" per microstep.

I put the software in
TestString = Track mode with 0.1 step per second.

I measure each
microstep position with a micrometer head for 4 full steps.

I
calculate the mean displacement for each microstep 0 to 1, 1 to 2
etc..

And more important I PUT THE CALCULATED DATA ON A GRAPHIC
SHEET.

This give me a nice smooth curve. I pickup the PWM numbers
for 0.025", 0.050", 0.075" and so on. I put back these
numbers in the config.dat file and restart the measurement and write
down. The result was almost perfect. I had to change the numbers of
only plus or minus 1."

Yet another suggestion from Juan Herrero: "I was going nuts
trying to measure and adjust the variances between the microsteps in
my Altaz controlled motors. I had 4 drinking straws taped end on end.
Attached to the stepper motor shaft. The end of the 3' straw
comptraction, would only move a couple of millimeters per microstep.
It was very difficult to take the measurements. And then...Mel
decided to improve his software from 10 to 20 microsteps! How could I
measure all those tiny steps ? Well yesterday I saw the light! Laser
light that is. I went to RadioShack and got their cheapest laser pen
pointer. Taped it to the motor

shaft.
And projected the beam on the wall. I can now measure microstep
movements 20mm big! TA DA!"

`Date:________
Computer _________ Dir:_________ Scope.exe`

`Compiled:__________
Telescope _____PCB ______`

`InvertOutput
0 0 for PCB`

`FR
Step Size
2.25 for ½ step, 4.5 for full step`

`HSTimerFlag
1 for IRQ8 (DOS), 0 for Windows`

`Max
Delay
2000 (DOS)`

`Min
Delay
1000 (DOS)`

`HsDelayX
N/A DOS, Multiplier for Windows slews`

`PWMRepsTick
Shoot for 20-60`

`MsDelayX
SlowPC=1, fast PC=6`

`MsPause
Current Control during MS`

`Motor Current`

`PWM[0]
a 100 Step0 = PWM[0]`

`PWM[1]
b 100 Step1=PWM[1]+PWM[9]`

`PWM[2]
c 100 Step2=PWM[2]+PWM[8]`

`PWM[3]
d 100 Step3=PWM[3]+PWM[7]`

`PWM[4]
e 100 Step4=PWM[4]+PWM[6]`

`PWM[5]
f 100 Step5=PWM[5]+PWM[5]`

`PWM[6]
g
Step6=PWM[6]+PWM[4]`

`PWM[7]
h
Step7=PWM[7]+PWM[3]`

`PWM[8]
i
Step8=PWM[8]+PWM[2]`

`PWM[9]
j
Step9=PWM[9]+PWM[1]`

`SETUP:
Pointer and scale on Motor, 10amp Range on Meter.`

`Calculate
current to meet wattage limit on Motor: V=IR, VRated * IRated =
WattsRated,`

`
Iops = WattsRated / Vops __________________________`

`1.
Start: Default PWM's, MsDelayX=1 for slow and up to 6 for fast,`

`MsPause=0,
PWMRepsTick=display in Track`

`2. Adjust
MsDelayX till PWMRepsTick = 20 <-> 60 (may increase current)
and motion is smooth.`

`
(Motion is smoother at lower PWM's, but current is higher and so is
sound)`

`3. Adjust
MsPause to get current within Motor Wattage Limits: (When current is
too low, motion gets
jerky)
Increase MsPause, Decrease PWM[x]'s or Decrease MsDelayX to
Decrease current`

`4. Adjust
PWM[x] Matrix for even steps (Larger PWM[x]'s decrease PWMRepsTick`

` If
spacing is too big: bring voltages closer together;`

`
if spacing too small, increase the difference in voltages:`

` If the
move between 0 and 1 is too big,`

`
reduce [9] to decrease how much winding B pulls off of centered on A`

` If
motor barely moves between 0 and 1,`

`
Increase [9] so winding B pulls it more off of centered on A`

` If
spacing between [3] and [4] is too big,`

`
increase [3] or decrease [4] (or both)`

`PWM
(winding A) Step #
PWM (winding B)`

`100
a 0--0--------------------0 a 100`

`100
b 1---1-------------------9 j ___`

`100
c 2-----2-----------------8 I ___`

`100
d 3-------3---------------7 h ___`

`100
e 4---------4-------------6 g ___`

`100
f 5-----------5-----------5 f 100`

`___
g 6-------------6---------4 e 100`

`___
h 7---------------7-------3 d 100`

`___
i 8-----------------8-----2 c 100`

`___
j 9-------------------9---1 b 100`

`5. Iterate
2-4 till current within wattage limit,`

`
PWMRepsTick = 30-60, and motion is smooth/even`

`6. Adjust
MinDelay and MaxDelay (and HsDelayX if Windows)`

`
to allow smooth and fast slews with no buzzes (Min Delay = Buzz)`

`7. Copy these
values into Config.dat`

Bob Norgard has written a webpage on adjusting
the microstep values. It is at
http://home.gci.net/~rnorgard/Scope/Microsteps

Tom Krajci has an Excel spreadsheet to adjust the microstepping. Logon and look at the scope-drive archives.