Need Help!- Newbie woes with Pololu A4983 and emc: high pitched noise and nothing else

[Lanthan]

Dear all,

I am having some trouble getting started with emc and a DIY X-Y table set up to learn EMC.

The steppers are salvaged from and old Star printer (Mitsumi M42 sp-1) and an epson scanner. They are wired as bipolar, and turn out to be a bit underpowered to drive the table, but work (see below).

The X and Y axes are driven Pololu's A4983 stepper motor driver carriers.
Those are connected to a Xydrive XD14 "high speed" parallel port breakout board.
Stepper drivers and parallel port breakout are fed with +5 V (wall wart) and +12V (3 Amp regulated supply)
Each axis has enable (inverted), step and direction pins, plus opto-switces for the limits.
The breakout board is connected to a netmos parallel port PCI card (bought second hand on ebay).
The computer is an AMD Athlon 64x2 4600+ at 2.4 GHz. It runs a fresh install of Ubuntu Hardy from the LiveCD (kernel 2.6.24-16-rtai sept 30, 2008). emc2 is 2.3.5

Max Jitter is 10'506 ns for the servo thread and 15'414 for the base thread.

The A4983 stepper driver spec sheet gives as minimal values:

• step high pulse 1 microsecond
• step low pulse 1 microsecond
• setup step time 200 ns
• hold time 200 ns

I fed those values to the stepconf wizard (as well as the appropriate memory address from the paralel port card)

The problem: when I try to jog the axes with stepconf, the only thing I can notice is a high pitched whine plus after a while some heating of the motors.

At least some sort of signal appears to reach the drivers and the motors (the noise changes with the jog buttons).

I tried modifying the timing values by a factor 10, same results

As a troubleshooting measure, I then connected an arduino to the a4983 drivers (in parallel to the breakout board connexions: nothing bad has happened till now...): I can get both axes moving OK when controlling them with the arduino.

On the arduino, I use loops of this sort:

digitalWrite(X_STEP_PIN, LOW);
delayMicroseconds(X_STEP_DELAY);
digitalWrite(X_STEP_PIN, HIGH);
delayMicroseconds(X_STEP_DELAY);

The values I have found to work best (smoother operation of the motors) with my setup are:

X_STEP_DELAY = 700 microseconds
Y_STEP_DELAY = 150 microseconds

So I suspect the problem with emc might be possibly the correct setup of timings. (the other possibility would be hardware: signal loss with a crappy parallel port cable).

But I am a bit confused: how could I translate the "correct" values into stepconf or the HAL file? Which parameters should I be modifying?


Thank you for any hints and help with this...

[chester88]

Did you confirm that EMC is sending out the step and direction signals to the right parport pins?

Did you confirm that the parport is actually outputting signals?

try timing with some ridiculously hi number such as 20 000 on all timing
settings just to confirm the signals are actually getting out and are slow
enough for the driver.

Does the parport output enough voltage?
some output 3.3v and maybe the driver actually needs 5?

[Lanthan]

Hi!
Thank you for the suggestions!
The 5 V source (a wall-wart supposed to rate up to 1.8 A) seems appropriate and outputs really 5V.

Meanwhile: The netmos parallel port card stopped showing at all with lspci, I suppose it went to board's paradise.
I brought back to life an old P4 with an integrated parallel port in the motherboard. Am getting step signals passed, sort of: one of the motors moves, one way only, whenever I test any of the axes. I also discovered the extremely useful hal parallel port tester.

The voltages I measure at the terminals aren't near TTL anyway. I don't have a scope to further test the signals, but there must be interferences all over: when I run the stepper I get almost all the other lines at around 1.5 V.
The main suspect for now is the cheap, extremely thin parallel cable from eBay.
Am recycling an old cable and soldering a very simple breakout board à la (Mantis ), will report on the outcomes.

[Lanthan]

The cable in the attached picture (the bottom one) is being sold in eBay (UK) as "Parallel Printer 25M/25M Cable 3M - Switchbox DB25". It looked suspiciously thin (5 mm diameter) when compared to some worn and proven parallel port cable (7.5 mm diameter, on top). Pin signals were inconsistent, and interference was all over. Time for an autopsy.

Inside, surprise, surprise, only 11 teeny wires are to be found. These connect pins 2, 3, 4, 5, 6, 10, 11, 12, 13, 15 and 25. No way this would ever work!
Still wondering how this got also the parallell port card to release the magic smoke: coincidence or not?
I am asking the seller of the cable, a computer parts shop, a full refund.

On top you see also my new, extremely elegant ;-) breakout on stripboard. Am getting 7404 inverter gates to connect the opto-detectors installed at the limits.

Greetings!