Stepper control - again

Coyoteboy

Senior Member
I'm really seeming to struggle with stepper control on a picaxe. I've recently tried to "hack" a scanner and want control over the stepper that controls the motion of the head. Easy enough me thinks. Nope. I scooted around the main board and found the driver IC (PBL 3775 http://www.wobit.com.pl/download/pdf/ulkady_scalone/3775.pdf) which takes two inputs per coil (bipolar, 4 wire stepper), as far as I see - coil polarity and "disable". Thinking this is simple enough I used the full step sequence from
http://www.piclist.com/techref/piclist/jal/DrivingBipolarStepperMotors.htm
to create this on an 08m:
Code:
let dirs = %00010111
; %--- P1 - D1 P2 D2
main: 
let pins=%00010001
pause 1
let pins=%00000110
pause 1
let pins=%00000001
pause 1
let pins=%00000100
pause 1
goto main
Wired the sucker up as per the code, low and behold the motor is stalled and refuses to budge. I tried a few different pause values to see if that eased it but nope. I'm going to strip this apart and rewire it, but can anyone spot a flaw in the coding coversion from sequence to pins?
 

manuka

Senior Member
Stalled? No twitching at all? What sort of ratings is the stepper? Power supply up to the task? Done some resistive detective work with a DMM? Tried a quick check with an AA cell across coil wires? Tried simple semiconductor based sequencing rather than motor driver IC?

A recent workout here with a mini stepper showed PULSOUT based 08M driving remarkably easy. See => http://www.picaxe.orcon.net.nz/stepdemo.jpg
 

Coyoteboy

Senior Member
Sussed it, it was twitching but didnt seem to have more than 0.2v output so I checked the datasheet again and realised Vr1+2 might need holding high, so i did - now it moves! woo
 
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