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Hello, I am new to the basicx but have done a variety of programming over the years...and I am running into a problem driving a stepper motor through a Parker DB Drive with standard step and direction signals. I have written two simple programs to send pulses to the stepper controller and I am seeing a frequency shift in the pulse train in each case. As a result the stepper is loping, running faster and then slightly slower and then faster over fractions of a second. The controller is microstepping 10000 steps/rev. I am able to see the jitter because I have a mirror attached to the stepper shaft and a laser bouncing off the mirror. I am after reasonable smooth motion. When I stick a scope on output I can easily see the frequency of the pulse train jittering by 20% or more. The variability scales with the frequency of the pulses too...so if I increase the pulse width, the jittering increases as well. Is there an inherent jitter in the clock of the Basicx? The first program is a simple pulse out pin 5. The second program uses the AutoCapture output...and I see the same result. Am I missing something here? Thanks for any suggestions... Regards, Russ 'First Program Option Explicit Dim PulseWidth As Integer Public Sub Main() Do PulseWidth = 1000 'Pulse Pin5 Call PulseOut(5,PulseWidth,0) Call PulseOut(5,PulseWidth,1) Loop End Sub 'Second Program Option Explicit Dim ToggleArray (1 to 2) as New UnsignedInteger Public Sub Main() ToggleArray(1) = 9000 ToggleArray(2) = 9000 Do Call OutputCapture(ToggleArray,2,1) Loop End Sub

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> ... frequency of the pulse train jittering by 20%... Yes, I suspect you are seeing a temporal artifact of multitasking. Both techniques you tried need to loop for each output cycle, so the loop time will vary as the OS performs its magic. In particular, since your ~2mS pulse width is very close to the OS tick of ~1.95mS, you might well be seeing a slow beat product of the two frequencies, making the effect more dramatic. Bit banging in a multitasking environment makes for a poor signal generator. Try PWM. Once you set it, the PWM hardware mechanism operates autonomously and should produce a continuous stable stream, although the available rates are few. I've seen others use an external 555, ramping it's rate with an analog output. You can bring it's output back to a pin to count if you need to know the motor's position. Tom Tom Becker --... ...-- www.RighTime.com The RighTime Clock Company, Inc., Cape Coral, Florida USA +1239 540 5700

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