NEW PRODUCT: Taptation Tap Tempo controller

[blearyeyes]

Well, I measured my MCP41100 and it's only 80K so there it is...
I'll try to get a better value digipot somehow, maybe someone on the forum could part with one? I'll gladly pay a premium for a good one!   

/Magnus

How did you measure the mcp chip.. I guess I'll grab a spec sheet and figure it out.

[blearyeyes]

Oh and one of the guys at Guitarpcb bought six digital pots and they made no difference.  This issue of the repeats being faster than the LED and non linear to boot was finally fixed with a new Taptation chip. It's rare but maybe we hit a bad batch.

http://www.guitarpcb.com/apps/forums/topics/show/13049613-dlay-tap-tempo-not-quite-right

Down a bit into the topic. User name is Attman.

I'm hoping to hear from Andrew

[blearyeyes]

Does anyone know how to get a hold of Tone God?

[mrsuspend]

How did you measure the mcp chip.. I guess I'll grab a spec sheet and figure it out.

If I remember correctly you measure pins 6 and 8.

/Magnus

[blearyeyes]

Earth calling Andrew...... Tone God, respond..

Taptation malfunction.

All avenues of recourse are exhausted....   

[ca cat]

I also have two taptations with simmilar problems on the bench..  I used the last one that  worked corectly in a full featured delay,  with tap tempo modulation and delay and it worked great!   So it would be nice to solve this problem.

[aron]

That is weird. I am burning the chips the same way. They verify on the burner so how could the chips act differently? It would be like the microprocessor is not running the program correctly. That seems highly unlikely. Someone did tell me the digital pots had a wide tolerance.
I can try sending another chip for you to test. Contact me though email. sales@diystompboxes.com

[blearyeyes]

Don't know if it makes any difference but the timing issue is happening with Tapping or with the speed pot.

[aron]

I wrote Andrew so lets see if he has any ideas.

[mrsuspend]

I still believe the digipot to be a far mote likely culprit.
It needs to be as close to 100K as possible. If it measures anything below 90k it will be unusable in terms of tempo tapping.
Please measure your pots and post the results.

/Magnus

[aron]

Maybe I shouldn't add the digital pot anymore if this starts becoming an issue. It's kind of like 1% resistors for biasing.

[aron]

OK, I think we are going about this the wrong way. Someone contact me and send me your circuit that is non-working with the problem. Email me and I will pay for shipping etc... and debug this.
Thanks!

[aron]

OK things are in motion.
Thanks!

[The Tone God]

Hey everyone.

Sorry if I haven't been around. The shop has been stupid busy for months. I also wanted to bread board the circuit and test it with the currently software. It seems to be working for me. That being said I am using lab gear and original parts.

I have had people contact me about these problems but a clear solution has not come forth. Some people clean up the wiring (the tempo pin on the PT2399 is very sensitive), some change the PT2399 (I think some people we using knock offs from cheap suppliers), and some change out the TapTation with a new one and find it works. Power supplies not being stable is another as any power fluctuation will change the clock on the PT2399.

Some fixes are putting a small trimming pot/resistor in series with pin 6 for tempos that are generally too fast. You can put one in parallel for too slow but on longer delays the timing might go out because you are introducing a taper to the restive curve. Also use a really stable power supply from a good regulator and filtered properly.

The digital pots are possible one point of error. Another is maybe the PT2399 has had a fab change somewhere that affects the timing. Honestly its all guessing on my part as I have no bad parts to test with.

The truth is this design has limitations, ones I am not happy with. That being said I have a proof of concept circuit on one of my boards for TapTation v2.0 that should *greatly* reduce these issues but I need more time to work on it. Also a bunch of new features will be added that people seem to be interested in.

Again sorry for the silence but I am here now.

Andrew

[blearyeyes]

Hey Andrew,

Glad your shop is busy.  I assume that's a good thing.

Just noticed something interesting...the modulation LFO is in sync with the LEDs at any tempo.

Don't know anything about how this works but I assume that the modulation function is separate from the digipot...?

[blearyeyes]

I'm getting ready to send a complete GuitarPCB D'lay build with Daughter Board to Aron that is exhibiting the faster repeats than LED issues.
I want to go back through the build and check everything first so I don't go to all the hassle just to find I put the wrong resistor in somewhere..

My first idea on GuitarPCB was to point to the digipot as it made sense..then someone sent the fellow a new Taptation chip and fixed his issues with the same boards I am using and the same issue I am having.
Would you have a TT chip that was burned apart from Aron's equipment just to eliminate the very remote possibility that a bit is corrupt or something weird is happening? I have two chip sets from Aron and they both exhibit the same issue.

[blearyeyes]

Hey Andrew,
Just noticed something interesting...the modulation LFO is in sync with the LEDs at any tempo.
Don't know anything about how this works but I assume that the modulation function is separate from the digipot...?

After studying the schematic from the daughter board it looks like the modulation is also running through the MPC chip so the answer is no, it is not separate.

DS

[The Tone God]

Just noticed something interesting...the modulation LFO is in sync with the LEDs at any tempo.

Don't know anything about how this works but I assume that the modulation function is separate from the digipot...?

Yes the LFO is in sync with the LEDs. It meant for either using in other modulation effects like phasers and tremolos or to act like the same modulation that Memory Man delays have. It is separate from the digipot.

I think the best course is for Aron to get the board and test with other TapTation chips he is programming. That way we can be sure his equipment is working fine. From there if there is still an issue I can receive it for diagnoses.

Andrew

[blearyeyes]

OK I'll send it all out.

Thank you guys. 

[aron]

After reading the original posts, think about it, the only interface between the delay and the taptation is the digital pot and pin 6 of the PT2399.
Now reference this:

The TapTation uses a 100K pot for a max around 1125ms

OK, there are 2 ways to debug this.

1: Tap something slow - like 2 seconds. This should set the max time to 1125ms (1.125 seconds). From the above quote, the LEDs should flash roughly 1.125 seconds AND the digipot should be around 100K.

If it's around 100K, the taptation is working properly - time to look at the rest of the circuits (PT2399 etc...)
If it's NOT close to 100K then the code that sets the digital pot is sending out an incorrect value (more unlikely) or, the digital pot is not close to spec.

So people, tap slowly and measure your digipot value. It looks like pin 5 of the digipot and ground of the PT2399. Does that make sense or am I overlooking something?
You probably have to pull the PT2399 and measure the digipot value.

Here's more food for thought. If you tap slowly and the LEDs flash slowly etc.... the timing code is working. The more I think about this, it's pin 6 of the PT2399 being extremely sensitive or PT2399 scaling differently.

SPI code is super easy:
http://arduino.cc/en/Tutorial/SPIDigitalPot