telescope stepper driver?

[garymck]

hi,
have just come across this telescope drve based on USB sound controllers. Looks good, but then I'm no electronics whiz. Has anybody here used it? Comments ideas etc?

Seems like a remarkably simple and inexpensive way to control and drive a scope?

http://soundstepper.sourceforge.net/#overvie

cheers
Gary

[bojan]

This is very interesting..
However, it seems to me this system still needs specialised audio circuitry (kind of analogue decoder to separate channels for RA and DEC from audio card stereo outputs, and audio card must have 3 outputs, so it is not standard with only L-R) with amplifiers (one stereo amplifier per motor), capable of driving stepper motors (couple of Watts for higher torque).. so this is not off the shelf product.
Also, those audio adapters and amplifiers must be DC-coupled (for very slow moving steppers, while guiding for example).

I am using one of those programs mentioned in a text as problematic CPU usage-wise (Bartels, it has to run in DOS mode), and it works great, despite the fact that it requires dedicated PC (cheap 100MHz pentium, running DOS).. However, if I find some time I may try and have a look at this, just for fun..

[garymck]

Hi Bojan,

found a link to some more of the developers stuff:

http://www.astrofotos.info/index.php/macielbassp/Projetos-ATM

I also used to use a Bartels drive (Avandonk bought my Bartelized EQ6 years ago), unfortunately Mel has ceased supplying/supporting the old stepper system.

cheers
Gary

[bojan]

Hi Gary, thanks for this additional info..
$12 (ebay) for adapters is not much, but it the near future the support/availability may be gone (and Mel is still supporting his system on yahoo group, if it really needs any support at all). However, the required additional analogue circuitry may be a problem for many.
I am still wandering how this guy (Maciel) sorted out DC operation of steppers (and microstepping..). And, it seems no encoders are supported?
It's time to download the software and have a proper look at it ;)

EDIT:
DC-operation is sorted out by using DC -coupled audio-adapters..
I tried the software on my desktop (with on-board audio adapter), it seems it works.. I can hear tones, as expected

This is definitely worth trying !!
Perhaps encoders will be supported via ASCOM platform?

EDIT2:
Power consumption/dissipation may be an issue (depends on how microstepping is done.. Class-d amplifier may be OK as it has internal PWM)

EDIT 3:
Conclusion - definitely worth trying.
However:
- No microstepping (bad... my EQ7 has 9arcsec/step resolution in full step mode, which is not good enough resolution for guiding. However, it might be quite OK for tracking as output seems to be sinusoidal)
- No direct encoder interface (must go via ASCOM, I hope..)
- Now I need to check the rest of functionality (and connectivity to other parts of the system - encoders via ASCOM, CdC or Stellarium... )
Otherwise.. OK.

[rally]

Pretty cheap solution ! $2 each for the USB Audio device

http://www.dealextreme.com/p/virtual-5-1-surround-usb-2-0-external-sound-card-22475

Now he just needs to add in some encoder feedback and a home position and that would be a real winner.

[bojan]

Don't forget to add amplifiers to the total bill.
Then the cost becomes very similar to Bartel's stepper system (which does all you could ever need..).

[bojan]

Well, couple of those USB-Audio dongles from ebay are ordered ...
So, after looking into output waveforms, I will know more.

However, it seems that the dissipation of the proposed current driver design (car radio amplifier) will be definitely too high (resulting in high current consumption), especially for low-resistance motors, so chopper should be used instead (for example, NJM3771, this chip is capable of handling 700mA per coil, enough for high-torque motors). Of course, the proposed driver circuit must be modified accordingly.

[Ayatola]

Hi Bojan and Gary.

I already used the Maciel's SoundStepper in our 16" Dob. The system works very well. Easy and cheap to assemble.

Now I'm working in a new approach to use the system. I'm building a EQ mount with harmonic gears and 5 phase stepper motors. To control this motors I bough a pair of specific drivers controlled by square pulses. To generate pulses and control the drivers I will use the SoundStepper.

16" dob base in action
http://www.youtube.com/watch?v=M-zQBYgdxMw

Some pictures of my small project.
http://www.astrofotos.info/index.php/Marcelo/ATM/Projeto-Clonus

[]´s
Marcelo

[bojan]

Hi Marcelo,
This is very interesting..
Are you going to obtain the special version of software (with square pulses)? Or you will simply shape them with Schmidt trigger and use harmonic reductor to achieve required resolution?
I would be interested in step-dir pulses from audio card (or anything else, for that matter..) - I already have drivers with Allegro chips (16microsteps), I am using them with my Bartel's system - but Maciel's approach may be more convenient because everything can run on single PC (instead of minimum two as it is with Bartel's scope.exe).

[Maciel]

Hi all,
Thanks Bojan for contact me by email.

The Soundstepper is pure software, it generates audio waveform only. Every circuit capable of convert these audio signals into stepper windings' current will work. Each stepper needs a separate USB audio device, L+R channels: each channel drives a winding.

I'm not electronic engineer, then I was not capable to design a full PWM circuit with current-feedback for use with Soundstepper. Instead, the analog design was quite obvious for me, and the dissipation / power consumption issues seems minor... The power consumption (current) is the same of stepper's total current, and the dissipated power is (supply voltage - winding voltage) * current. Much more than PWM devices, of course. But works great!

About some questions in this thread:

1- Soundstepper works with standard 2-channel audio devices (don't need 3-output audio cards). Up to 4 steppers, using a separate audio adapter for each.

2- No, Soundstepper don't support encoder feedback at all. Is on the roadmap, but not for this year. My priority now is finish the field de-rotator algorythm.

3- Class-D USB audio adapters (SJ-588) are treated as analog, the output waveform is low-pass-filtered.

4- Yes, Soundstepper does microstepping: 90 microsteps per step (much more than stepper's accuracy). You can check this with a laser pointer on a stepper axis (using Soundstepper's "static positioning test" option). Like these: http://www.astrofotos.info/index.php/macielbassp/Projetos-ATM/GoToLaser - These "poor man's direct drive mount" have less than 10 arc-minute accuracy over the entire sky, and less than 2 arc-minute for tracking an object over 1 hour, with no reduction, the steppers' axes are the mount axes! Use the "reduction calculator" at http://soundstepper.sourceforge.net/#steppersmounts - For visual use you can use reductions as low as 1.5 arc-minute per full step (like our 16" dob), and for astrophotography, 10 arc-seconds per full step is fine.

My audio analog circuits are SUGGESTED, and You're free to propose a new, better circuit. I'm very interested in Bojan's approach with NJM3771!

The basic guidelines for circuit design for Soundstepper is:
1- all DC coupled: at low speed it is very important.
2- stepper windings current feedback: the audio output level need be translated into current (no voltage), because the current (not voltage) generates torque. At high speed it is very important.

The "pulse/direction" version are now available for download at http://soundstepper.sourceforge.net (is an option in "test and adjust" window). With this option checked, the left channel is pulse (90usec width), and the right channel is direction. Depending on the output voltages of the audio devices, and drive inputs, the audio signal may need to be passed through low-pass filters and "schmidt triggers."

Thanks for the interest, and sorry for these long text in bad english.

[Ayatola]

Hi Bojan.

Maciel was faster than me and answered their questions :)

I will use two 5 phase driver to control the motors. I hope that does not require any other electronic to control it but it only depends of the soundcard output voltage. The driver need a 4.5v pulse to work.

With this approach I expect get 250 microsteps (resolution of 0,0000576º or 0,207 arcsec with a 1/50 harmonic gear) and 2 selectable speeds.

Maciel already modified Soudstepper to use square pulses to control this drivers, now I need expend some time to perform a lot of tests.

I'm using this driver to this project:

http://www.orientalmotor.com/products/pdfs/connection/RK_connection_operation.pdf

[]´s
Marcelo

[Poita]

Looks like lots of fun. I used an audio signal to drive the stepper motor on my telecine rig a while back. I'll have to give this a go.

[bojan]

Hi Maciel,
This version (with step-dir pulses as output) is potentially absolute winner :thumbsup:
Now I can use my driver modules (http://www.pololu.com/catalog/product/1182) with your system, and the interface circuit might be much simpler than before.
Looking forward to test..

EDIT:
I have suggestion: Could you try and use mic input of those USB audio adapters for encoder quadrature signals (DC coupled. of course..)?

[garymck]

Ho Maciel,Bojan and Ayatola,

I'd love to build a drive using this approach, but am not electronically literate enough to follow the diagrams on soundsteppers page. I am able to build with a simple diagram to work with (managed to complete a Cookbook 245 ccd that worked) so is there anywhere I could find a really easy diagram of some electronics to build? A Dummies guide would be really helpful.

cheers
Gary,

[Maciel]

Bojan, Soundstepper with "pulse/direction" drive method is far easier to interface with automated stepper drives....

BUT this way it loose the microstep feature: while using analog drive method, the Soundstepper does 90 microstep per full step. Using pulse/direction drive method, the Soundstepper "step" is a single pulse. The microstepping is now a drive's responsibility, and have a microstepping drive (or a BIG reduction) becomes essential.

Is possible to design an analog-controlled PWM drive with current feedback?

Garymck, what do you mean with "simpler diagram"?

[bojan]

Hi Maciel,
It is possible, and I am working on this (the idea of using NJM3771 or similar driver is the answer ;) )



I am aware ot that. The Allegro chip that I am using as stepper driver provides 16 microsteps, and in a combination with 0.9° steppers gives me enough resolution for smooth tracking (0.23 arcsec/microstep)

[garymck]

Maciel,

I mean something that show a component layout on a a piece of stripboard like the diagrams on this page:

http://www.kpsec.freeuk.com/stripbd.htm

That way electronics dummies like me can simply put a component where it has to go rather than having to build a rats nest of wires . I'm sure the electronics parts are what stops lots of people from using your system. some of us need the equivalent of a "paint by numbers picture" .......

I've oreder 6 usb sound dongles hoping to follow someone elses lead....

cheers
Gary

[bojan]

Gary,
you have the links for what you need on Maciel's page, a bit lower from the middle of it :
http://soundstepper.sourceforge.net/Protoboard_for_SJ588.html

[Poita]

A PCB wouldn't be too hard to make from that diagram either.

[MrB]

Hi Bojan,
Which chip are you using?
I have just ordered a couple of A4988's to experiment with.
What are your thoughts on the Allegro's? It seems some people have been having problems with missed steps at low speeds and low currents while microstepping at x8 and x16, tho apparently the A4988 handles these conditions better than others like the A3977/79's

[garymck]

Thanks Bojan,

I had missed that link....will start building whilst awaiting arrival of USB dongles....

cheers
Gary

[bojan]

I am using A4988 (http://www.pololu.com/catalog/product/1182), no problems observed so far.

[MrB]

Haha classic, that's what I ordered last night, tho the clone version: StepStick (http://reprap.org/wiki/StepStick)
Good to know you've not had any issues. Thanks.

[bojan]

Audio adapters arrived today - Fake SJ588 (blue transparent case), 4 pieces.
Because it is better to use two adapters of different varieties (so the w' doesn't confuse AR and DEC), I ordered additional 4 (grey cases).
Tomorrow I'lll have a look at waveforms.. however Maciel told me the common is actually at 2.5V respective to PC ground, so it will not be a problem to design the electronics for NJM3771 (full wave rectifier (for input voltage to NNJ3771) with OPAMPs and comparator ( to generate Phase direction signal for NJM3771).
The concept schematic is attached, however there is some work to be done in relation to output level shift and components values need to be finalised.
When I am finished with this, I will post the final schematic.

[Maciel]

This protoboard diagram is not simple enough?
http://soundstepper.sourceforge.net/Protoboard_for_SJ588.html

[Maciel]

Don't start yet, first check the SJ588 chipset and output voltages. 2 years ago every SJ588 had TP6911 chipset, but now there are TP6911, CM109 and CM119 models, with different output voltages' behaviors. :sadeyes:

[bojan]

Hi all,
I checked the waveforms on my "fake" SJ588, and they seem OK (http://www.ebay.com.au/itm/USB-2-0-3D-Audio-Sound-Card-Adapter-External-Virual-5-1-Ch-Win7-64-Vista-f-PC-/110743682361?pt=AU_Components&hash=item19c8d67d39).
(BTW, it is not quite what was advertised - it has only one red LED, and on ebay photo I can see two.. but it doesn't really matter).
Reference (2.5V) is at left side of the large ceramic cap placed between audio sockets, as marked on the photo (other side is GND).

Now, based on that I did some simulations of the circuit for 3771 driver, see attached. I will make the protoboard using this circuit and see how this behaves - I am pretty confident it will be OK.
This circuit produces two waveforms: one to modulate the current in one motor coil, another one is logic level for direction of the current though the coil (this signal is required as input into 3771 stepper driver).
The interface schematic for RA (we need another one for DEC) is also attached.

As for step-dir mode of operation, this is straight-forward - just a couple of Schmitt triggers will do, the pulses are already referenced to PC GND.

[Ayatola]

Last night I tried to test one 5 phase motor with the Vexta driver and SoundStepper in pulse mode.

Unfortunately, my audio device don't worked as well. It is a fake device.

Today I performed a test using a parallel port. The driver and motor worked fine!

Tomorrow I will get a new USB dongle with Maciel and perform new tests ;)

Marcelo

[bojan]

Waveform straight out of audio device is not really good, you need to pass it to a schmitt trigger, preferably HC-type (if you are using C-MOS ... HC has threshold around 2.5V (for VCC 5V), while HCT, has it much lower - so noise from audio device (there is some) may trigger it and then you will have multiple pulses. Or, you should use comparator (opamp with some positive feedback to have small hysteresis for noise immunity).
You have to have a look at waveform with oscilloscope to be sure what is really going on.

[Maciel]

Yes, seems identical to my "fake" (a CM-109 chipset). But the output voltage swing of mine are from 0.38V to 3.91V, centered at 2.13V

You can measure the impedance of "ref" line? If is high (>100 ohms), is not suitable for my analog circuit "for SJ588", being preferrable use the "for HY544" version (and replacing "common" to "USB ground").

Maciel

[bojan]

I will try and let you know as soon as I i can (today is Saturday, and my wife wants me to do other things today and tomorrow - so this will have to wait until I escape to freedom of my lab at work :P) .

[Ayatola]

Hi all.

A small video showing SoundStepper controlling a motor in PULSE/DIR mode.

http://www.youtube.com/watch?v=YDY51-YFy-s

I need modify some issues in the soundcard but now it works fine without any intermediate electronic (schmitt trigger or low-pass filters).

[bojan]

Marcelo,
Was it hardware or software issue (can we have that version of software)?

[Ayatola]

Hi Bojan.

I connected the driver in the USB dongle using a P2 plug, but this is not the correct way to connect it. I need use the USB ground!
Using the "common" output plug we have a oscillation of 2 volts in this "false ground". This probably cause lost steps ans a lot of noise. Today I will test it using the USB ground.
I will let you know about the tests...

[]´s
Marcelo

[bojan]

OK, I've got it..
It seems that there is variety of those dongles on the market (after all, Maciel mentioned this on his website, but I fully appreciated what he wrote only after I measured my own specimen and when I saw what I saw).
Attached is the screen shot of step pulses from my dongle, there are some artefacts from (built-in) digital filter visible (ringing), so pulses are not clean - but they will be OK after Schmitt trigger.

BTW, the second batch of dongles arrived from ebay this morning (grey ) and they are the same as the first, with blue case.

Interestingly, the waveform depends on OS running - the second shot is from w7 (the first one is from laptop running xp) - most likely because I didn't configure the audio driver properly in w7, so the OS is interfering with SoundStepper). Please note, the second shot is scaled as 0.5V per division (GND is at the bottom of the screen graticule) and in both cases, the audio level was set to 120%.

Anyway, this is all very good - the whole system - telescope, guiding, ASCOM, star charts- all running on a single desktop. And all of that is freeware.
Of course, driver electronics must still be built, but with those Pololu or StepStick PCB's around, this is not a problem...

[Maciel]

Soundstepper experimental version V5.0.1.198, with 44100Hz audio sample rate (was 22050) and configurable pulse width:
http://sourceforge.net/projects/soundstepper/files/SoundStepperV5.0.1.198.zip/download

[bojan]

This looks even better- see screen shots for 100% and 120% volume setting (and default width 47us).

[bojan]

Finally, here is my board (with Pololu drivers), at the moment controlled with SoundStepper (This board was originally designed as Bartels interface for EQ-6, that is why there is that 26-pin IDC connector on the left side, plus additional connectors for keypad and focuser).
Motor on the picture is 1.8° step/rev, and it works at maximum speed SoundStepper can deliver with no problems observed.
However, the current adjustment is critical: if too low, microstepping disappears, if too high, then the movement becomes jerky for some reason.
Later I plan to fit the heavy wheel on the motor shaft, this should help to further smoothen the movement.
Very happy ! :thumbsup:

[Rod]

Hi Bojan

I have been following this with great interest. Great to see the work you are putting into it.

How do you think the slew speed compares with bartels? How noisy are the steppers when tracking?

Thanks

Rod

[bojan]

Hi Rod,
The noise seems to be minimal because the microstepping PWM frequency is higher than I can hear (~50kHz - this depends on inductance of the motor coils, of course).
Max speed from SoundStepper is around 2k pulses per second, resulting speed is similar to scope.exe (I am sure motors can do better than that, since here I am using high current, low voltage bipolar steppers, while on my dob I have steppers from old 8" floppy drives, operating at 36V or so.. and the PWM from scope is audible.
Also,please note, mechanical reduction will be different - much lower so slewing will be faster than my dob - so here I have 15° for 30 sec (half degrees per sec).

[Rod]

Sounds promising. Will you be testing it on a scope under the stars?

Rod

[bojan]

Yes.. when time permits.
This system (or another one, with L298 drivers) will go into my EQ6 anyway.

[Maciel]

Why?
The max pulse rate from Soundstepper is 10800 pulses/second.
Or it's having malfunctioning if using more speed than 2K PPS?

[Maciel]

I didn't understood this. "Current adjustment"... It's "volume"? In "pulse/dir" drive method, use the "volume" always at max (120). In further releases I will disable this volume control when using "pulse/dir" drive method.

[bojan]

Maciel,
current adjustment is on Pololu module (small pot that controls max current) it has nothing to do with SoundStepper - sorry I wasn't precise enough :D

[bojan]

While playing with Soundstepper, I noticed arrows on keyboard are not active while tracking. Also, it would be good if we can control the speed of the movement (like, when arrow key is pressed for longer time, acceleration kicks in)?

[bojan]

Sorry for error - yes the settings were as you described (at max).
I have some issues with noise on my board, when I have a oscilloscope probe attached the motor movement is jerky - I need Schmitt triggers instead of inverters (which I have currently on board (no need for them when signals are coming from LPT port).

However, the settings on the test screen (when I accept the previous telescope position) are shaded and can't be adjusted, and the max speed is defaulted to 2720sps.
I think you should get rid of those dialogue screens (optionally.. they are annoying once the whole thing is properly set up)


Unrelated to SoundStepper, there is a thermal problem with stepper divers - at higher currents, thermal protection on Allegro chip kicks in. So better cooling of driver modules will be necessary.

[Maciel]

The keyboard arrows are active while tracking, but the Soundstepper window must be in foreground.
Using Shift+UP increase arrows' speed, Shift+Down decrease arrows' speed. Releasing arrow, return to sidereal speed.

You can also use the "Guiding incorporation" feature: X% of guiding speed to be added to the sidereal speed each second. After guiding always "westward" for an amount of time, the Soundstepper adds X% of this guiding speed, integrated over the amount of time, to the sidereal speed, reducing further need of guiding. See "guiding incorporation" in main config window.

[Maciel]

About the max speed, I can't reproduce the problem here (see screenshot).:question:

About initial "recover from last saved position" dialog, it's very important if the system crashes. How the Soundstepper will know if the telescope was properly parked?

But I may put in this dialog a 4th button, "check configurations", and make "OK" button bypass config window. What about this?

[bojan]

Not sure now.. maybe I was using older version of software (too many computers around.. maybe I will need to run SS from memory stick while experimenting :shrug:

Nope.. see attached.
I can change the speed parameters only if saved settings are discarded.




The first dialogue box ("is telescope in the same position?" ) is quite OK.
If accepted, application should start without intermediate dialogue (test screen), but the idea about 4th button on application screen ("check & change parameters") seems better to me - lets try it :thumbsup:

I have one more question - I noticed when GoTo, SS sometimes overshoots, then goes back quite a bit, then resumes tracking. I am assuming this is correction between estimated and required amount of slewing? How does SS know what sound card did (how many steps)?

[Maciel]

You can't change parameters when telescope is not parked. It's intentional. Discard current position (and accept the telescope is parked) is necessary to change settings (and is different from discard settings).

When Go-To (by coordinates) this is not expected to happen. But, when using keyboard arrows, yes. It will stop at the point where it was when You released the arrow.

[bojan]

Ok, this is reasonable...




This is what I was talking about.
For example, if I change RA by 1 hour (or whatever large amount), it will overshoot and come back a little, until it stops (or continue tracking).

EDIT:
OK, I may have remembered wrong thing when playing with software.. it is OK, as you wrote.

[bojan]

I just replaced 74HC04 with 74HC14 (Schmitt trigger) in my driver board and now the motor movement is smooth, no noise and no missing pulses at all. Like gliding on oil :thumbsup:
Only remaining issue (apart from those little general and not very important comments on SS software) is cooling of the driver module - I will sort it out with heat sinks and couple of thick silicon pads (for better thermal contact).
And, before I forget, it is worth mentioning that I also shorted R4 (10k) resistor on pololu board, marked with blue arrow on image below. This is to remove the missing pulses issue (more details are in data sheet for A4988 chip).

Very happy !!!

[Maciel]

New version of Soundstepper (the behavior of test window controls was improved):

https://sourceforge.net/projects/soundstepper/files/latest/download

[garymck]

Hi Bojan,

my cheap usb devices arrived from China. I can't see any markings designating the chipset used. They do look a look identical to yours except that one socket is yellow instead of gray. Is there a specific place I can find the chip set? If they are the same as yours, can I copy whatever circuit you finally use?

cheers
Gary

[bojan]

Gary, if they look the same then you will be OK, I guess.
plug them in and see what SS says - mine identifies itself as "Generic USB Audio device".

For now, I plan to use SS in pulse/direction mode with /Pololu stepper drivers.
When I am finished with details, I will post the schematic here.

I am not sure when I will have time to finalise the 3771 driver interface - it seems I will be very busy at work in next couple of months.

[Maciel]

New EXPERIMENTAL Soundstepper release, with:

- 16-bit audio: In earlier "8-bit audio" versions, the volume "120" was only 93% of volume (8-bit PCM audio: -128..0..127). Now it reaches 100% of 16-bit range. Attention: some audio adapters are non-linear at max volume (distortion).

- Floating-point analog positioning: Now there are infinite "microsteps" per step (true analog). In earlier "integer" versions, was 90 microsteps per step. This don't increase accuracy, but increase smoothness in ultra-low-reduction systems.

http://sourceforge.net/projects/soundstepper/files/SoundStepperV5.0.3.207.zip/download

Waiting for testers...

[Ayatola]

First video of the new equatorial mount (using harmonic gears) with SoundStepper in pulse/dir mode.

http://www.youtube.com/watch?v=RIZf3yHubxM

[]´s
Marcelo

[bojan]

That looks very good, Marcelo.
BTW, any news about new release of SoundStepper?
I set it up with my EQ6 and Pololu drivers, and it works perfectly, better than Bartel's system (which I still use on my dob mount, and I will as long as the computer running it is alive) .

[Ayatola]

Hi Bojan

I'm using the last release (5.0.3.207) in 16 bit mode. In my case I can't see any difference. Probably this change it is more important to the analogic motor control.

Some small bugs are corrected too.

Now I need to study the source code to add some improvements and help SoundStepper's development.

[]´s
Marcelo

[Maciel]

There is a new version (currently 5.1.0.234), fixing a serious bug that produces audio clicks and pops during and after high speed moves. It affects all users, but worst who is using analog drives.
Look for latest version at http://soundstepper.sourceforge.net/
Maciel

[bojan]

Hi Maciel,
Thank you for letting us know - I will update my copy right now.
I didn't notice this bug yet (probably because I am not using your software much recently - no time for anything else but work unfortunately..)

[garymck]

Hi,

have just found the correct USB to audio adapter for this project here:

http://www.ebay.com.au/itm/5-1CH-USB-3D-Audio-Sound-Card-Adapter-Headphone-MIC-2-0-External-/110913772468?pt=AU_Components&hash=item19d2f9dbb4

$3.95 each delivered. Took 2 days to arrive. Have just ordered more. They are the genuine SJ588 that Maciel recommends.

hope it helps...

Gary

[Maciel]

Hi Gary, good news! What is the audio device name on Windows? "USB AUDIO"? The L/R outputs and common are all at 2.5V in silence? If yes and yes, it's a genuine TP-6911 based device, the best for analog drives.

But for pulse/direction drives, the most of fake device works well, using schmidt triggers.

Using pulse/direction drives, the fake devices are even better than true TP-6911, because it is a PWM device, then the outputs must be low-pass-filtered (twice!) before schmidt triggers, while fake devices have "B-class" analog outputs, and must not be filtered.

[garymck]

Hi Maciel,

they report as USB audio. Have had bthem open and they look just like your pictures. The only difference is they have one led not two - though there is space on the circuit board for the second one. I've got 2 of them with another 8 on order (4 for me and four for a friend..)
cheers
Gary

[Maciel]

Hi all,

I created the Soundstepper users group, for better support users:
http://tech.groups.yahoo.com/group/soundstepper/

[Maciel]

Hi all,

The SoundStepper documentation was updated, with 2 new pages about the
hardware:
- How to choose, buy, test and recognize the USB audio devices;
- Suggestion of filter to couple USB audio devices with pulse/direction drives.

These are the 2 first links on the "hardware" section of main page:
http://soundstepper.sourceforge.net/index.html#hardware

P.S: English readers, please alert me for possible language mistakes.

Maciel