redoubler
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alwynallan
Doesn't seem to be working.
Hi Peter,
When I plug my DIY version into USB, it enumerates as a microphone, and the light starts up when I start monitoring the microphone's levels' but listening to it through PC speakers sounds like a square wave. Similarly when I probe the external resistors around the op amps I see square wave at about 19.23 Hz, 4.8V peak-to-peak.
I tried both 8.2K and 9.1K resistors paired with the 10K's per your diagram. at the op amps I should be seeing something more like the scope-like traces you put in the README, right?
I'm thinking there may be something wrong with the clock generation that is feeding the S/H's. Any ideas or suggestions? I'll see if I can send that out to a pin as well.
P.S. the blue LED on the board is flickering, but the pulse width is rather narrow, so it doesn't get very bright. It is at least interesting in that the pulse width in varying.
S/H clocks are running at 357 KHz which seems in the right ballpark, though a little slow if I calculate 45MHz / 48 / 2. I'll try looking at the wiring diagram from this fork to see if there might have been something different. But they look too close to square to be consistantly non-overlapping.
I looked carefully at your photograph at the top of your forked GitHub page. It looks like you have a pair of resistors connected to both GPIOs 3.2 and 3.1, but they should only be connected to 3.1. Similarly, you seem to have a pair of resistors connected to both 0.3 and 15.5, but they should only be connected to 15.5.
Maybe you interpreted the black curved arrows in my diagram (repeated below) as a connection. It was supposed to show where the connection used to be in REDOUBLER, and where I moved it for REDOUBLER-DIY.
That would explain the fixed frequency oscillation, because the old GPIO pins (3.2 and 0.3) have capacitors connected on the board for use improving A/D performance.
When it's working it should look like the traces I showed when connected to an oscilloscope. I used the internal A/Ds to record the traces, and feed the data out though a debugger. I would be interested to see how they look on a scope.
The LED is supposed to flicker randomly when the device is generating bits.
Thanks for keeping me posted.
[image: Inline image 1]
A. Peter Allan · 450 Timber Lane · Devon PA 19333 · 610-687-1708 · 610-547-4836 mobile
On Mon, Jun 27, 2016 at 11:49 PM, Burt Harris [email protected] wrote:
S/H clocks are running at 357 KHz which seems in the right ballpark, though a little slow if I calculate 45MHz / 48 / 2. I'll try looking at the wiring diagram from this fork to see if there might have been something different.
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Ahhh. Yes, I interpreted the black arrows as jumpers.
Thank you Peter, I do appreciate your spending the time to help.
OK. Rewired as you intended, and I get scope traces a lot closer to the data you plotted, [have a look.](
The bad news is that more often than not, the sound output still sounds wrong, but pressing reset repeatedly I do sometimes hit a condition where it sounds more like white noise. But even that, the frequency domain analysis suggests is a repeating pattern.
@alwynallan, please have a look at the new graphs at https://github.com/BurtHarris/redoubler-diy, it seems pretty clear what I'm getting is not truly random. Could you post some output from your device recorded by Audacity?