Incompatible Uno ??

[shabbee]

I have a Uno clone with an odd symptom.  When I adjust the filter most of them result in the sound breaking up and distorting really badly to the point that audio becomes silent. With another board (clone that uses a surface mount processor) it all sounds fine. I have verified the A/Ds are working on all ports so not sure why this is. My reason for posting is to make people aware. If I solve it with a new processor I will let you know. If anyone else has seen this and fixed it pls let me know

[paulsoulsby]

Thanks for the info.  That's very strange, considering the filter is digital and all processed within the Atmega.  My only explanation is that they haven't accurately cloned the ADC on the Atmega328P.  They've cloned enough of the parameters for the standard Arduino analog read to work, but not everything.  The Atmegatron libraries don't use Analog read and they scan the pots at a faster rate. 

Interesting to know that you've had this issue though.  I'll look out for this when I'm testing cloned Unos.

Paul

[shabbee]

As far as I can see, the microprocessor is genuine, the pcb is not though hence my struggle to understand why there is an issue.

[paulsoulsby]

Ah -but quite often the Atmega328P will actually be a clone, even though it looks totally genuine.  I've found this with quite a few cloned boards. If the software doesn't upload every time or the upload bombs out half way through, this can be because of a cloned Atmega.  Always worth having a genuine Uno at hand, to test for problems like this.

[shabbee]

Completely agree, this is what I'm finding, I learned about the LGT8F88A today. After spending 90 minutes trying to burn a bootloader into the net ATMEL328, when the device ID came back as 000000 got me thinking about fakes. For the time wasted trying to resolve problems the genuine arduino is money well spent. I just need to figure out how to skip the id check (something about adding -F) and see what happens then but I may find I still have audio issues. 

Thanks for your support

[shabbee]

Update!!

I burned the bootloader and the synth appears to be ok with the new 328P. I have another clone with the surface mount 328, this is not right so can only assume the chip is a clone of some variety. Seems to behave like an uno for the simple things buy guess it ain't up to digital synthesis.  I've ordered genuine arduino today so I have a reliable reference.

[tonalaxis]

Mmm, I've just realised my MiniAtmegatron might have the same issue with the cloned board. Some filters sound fine but some do indeed sound scratchy and to the point that there's no audio in some cases.
I just put it down to being normal behaviour.

[paulsoulsby]

I would be interested to hear an audio clip of this problem.  I may be able to work out what's going on.  Some of the filters do breakup, especially with the high resonance settings.  However the standard ones (filters 1,2,3,4) should all be totally stable.  Obviously filter 0 (off) should be totally fine!  I'm wondering if a slightly loose pot would cause this sound - if it was continuously sending out noise-like data.
I load and verify the software on each Arduino before shipping, but there's always a possibility that there's an issue with it. I've not come across it  myself as yet though. 

[tonalaxis]

I'll try and get a video emailed to you today to see what's going on.

Cheers

[tonalaxis]

FYI I went through this with Paul via email and everything is ok with my MiniAtmegatron.

Really good response and support.