[DigiSoft]

I assume you have read these two sources?
LiniStepper, lini, stepper, linear, 6th microstep, linear microstepping stepper motor driver, constant current linear driver, circuit Linistepper boards, LiniStepper kit, hobby stepper, robot stepper driver kit, CNC stepper driver kit
PIC Linear Stepper Motor Controller
The source code is included.
Al.

Sure I have but I don't understand ASM.

[Al_The_Man]

Sure I have but I don't understand ASM.

There is only 35 instructions and the 16F628 manual explains them all.
The free MPLAB S/W also has user manuals & guide.
Al.

[RomanLini]

Hi again, I will explain the operation in simple terms.

The PIC generates analogue voltage steps, to give 6th microstepping (1200 usteps/rev).

This is done by setting the PIC pins HI or LO, which goes through the diodes and resistors and makes a fixed analogue voltage at the bases of Q1/Q2, and another separate analogue voltage at the bases of Q3/Q4. These are two independent "DACs".

Then the small transistors Q5,6,7,8 are used as "killers" which always hold two of the output transistors off.

So the combined effect is 2 independent analogue voltages (one voltage for each motor phase) and always two of the main transistors on (which gives 4 combinations, ie 4 "fullsteps" in total).

The main transistors are driven linear, by analogue voltages, so there is no PWM needed, and the current through the stepper motor coils is constant and smooth.

However to get 18th usteps (3600 usteps/rev) the Lini can PWM its outputs to produce more usteps between the hardware usteps. However this still makes a constant analogue voltage at the bases because the PWM is filtered by the DACs and C5/C6 to make a constant DC voltage.

People's attempts to simulate the Lini don't work well because simulators are just not very good. If you want to get the very smooth linear current ramps as shown here;

that naturally occurs at the right speed, as the Lini is "tuned" using caps C5/C6 to be very smooth during a particular RPM range, where resonance often occurs.

[p55xp]

Hi again, I will explain the operation in simple terms.

The PIC generates analogue voltage steps, to give 6th microstepping (1200 usteps/rev).

This is done by setting the PIC pins HI or LO, which goes through the diodes and resistors and makes a fixed analogue voltage at the bases of Q1/Q2, and another separate analogue voltage at the bases of Q3/Q4. These are two independent "DACs".

Then the small transistors Q5,6,7,8 are used as "killers" which always hold two of the output transistors off.

Thanks Roman,
Your explanation in 'simple terms' enriched me, I assumed that 18th microstep positions are achieved by fast changing between these DAC output in right proportion in the software. But I still cannot understand why D3 and D6 is used in reverse direction with respect to D1, D2 and D4, D5 respectively, where D1, D2 and D4, D5 blocks 'back flowing' in the DACs.
Many many thanks again for the above post.
p55xp

[KOC62]

D3 and D6 ensure that the controlled discharge pathway is separate or independent from the charging pathway, of C5 and C6. Hence their reverse polarity when compared to the other diodes.

[p55xp]

Thanks a lot KOC62 for your prompt response. Now I must try again to evaluate the hardware in context of PIC code, and write again if face any problem.

p55xp