I am implementing a stepper motor half step driver in PSOC5 using the following techinque : http://www.8051projects.net/stepper-motor-interfacing/step-sequence.php

I am using a 3*4 LUT with the 3 inputs should be connected to a counter, but the problem is that the width of the 3 inputs is 1 bit while the width of the counter bus is 3 bits.

is there a way to seperate the bus into the original 3 bits??

the attached picture might help.

Drop the counter and use a registered LUT with 3 inputs and 7 outputs. The 3 inputs are to decode 8 states, from the 7 outputs 4 are for the stepper and three are the current states.

Bob

 do you mean that a registered LUT change states according to the input clock?? and why do I need 7 inputs?

I didn't say you need 7 Inputs, I said you need 3 inputs.

Bob

A registered LUT changes state on the clock.

An unregistered LUT is simply combinatorial logic, so changes on inputs,

reflected within prop delays on output.

Generally speaking registered LUTs used to synch states, and allow for

fdbk from outputs back to inputs. An unregistered LUT can make a great osc-

illator if you fdbk outputs to inputs....

Regards, Dana.

I thought of something like this...

Bob

Thanks Bob it worked just fine :).

and this is the first time I notice that Dana ACTUALLY USED A SMILEY  .......... thanks Dana and welcome to the dark side :D

Fine to hear that!

To give you some more hints for your LUT, you may specify to have a Left/Right input which may switch direction....

Bob

I am not using any smileys here (though I would like to) because the forum software hangs with a window where I cannot make any selection.... (sh**!)

Hahahahaha and now Bob is cursing too!! I think that both of you just joined the dark side .

one more question: instead of using a clock I would like to use a simple low to high transition to activiate the LUT. I have thought of simple attaching a Pin and using the following API:

while(1)

{

Pin_Write(0);

Pin_Write(1);

}

but this did not give the desired outcome. what am I doing wrong and is there any other means of a low to high transition (using software to control it)??

You might need an internal clock for the LUT (the data sheet just says 'you may select any clock in the system').

You could use an Edge Detector component to get a single pulse from an internal clock each time your input changes fro low to high.

Or you add another input to you LUT, which acts as enable input, and use a DFF as trigger to allow the LUT to advance exactly one time to the next state.

To generate a pulses controlled by your program directly i would suggest to use a Control Register UM connected to the LUT.

For a stepper motor it seems desirable to change the rotational speed on-the-fly according to the motor-specs. So the clock could be a varying clock made of a PWM (it has a Kill-input) and varying period.

Keep in mind: everything you put into the hardware parts of the project reduces the burden of the CPU.

Bob

Silly me not to think of a control register :(

But using a PWM (or even better: a NCO) for controlling the PWM speed is even better. Together with a counter to control the number of pulses it sounds like a good component for the library.

(Sometimes one really wants to execute single steps under version control)

 the control register worked perfectly. thanks everyone :)

You're welcome!