[sdiy] Jack insertion detection

[O Gillet]

(For digital modules only!)

I send pseudo-random noise on the switch. If no jack is inserted, this
pseudo-random noise will be received by whatever input circuit reads
the signal (op-amp + ADC ; transistor inverter + GPIO...). For
Rings/Warps I low-pass filter the correlation between the read and
expected value and apply a threshold on that. On more recent modules
(Stages/Marbles/Plaits), I simply count the % of matches within a
block of 64 samples.

Fun bit: if you actually send a random signal to the input, there's a
very low probability of mis-detection, but winning the lottery is more
likely anyway!
On Mon, Jul 23, 2018 at 11:24 PM Tim Ressel <timr at circuitabbey.com> wrote:
>
> Hello supremely helpful folks!
>
> I've got another challenge: how to detect when a plug is inserted into a
> jack. These are 3.5mm mono jacks btw. The current method is to use a
> stereo jack. When a mono plug is inserted the ring connection gets
> shorted to ground by the sleeve of the plug. This method works well, but
> the stereo jacks are taller than the mono jacks.
>
> The only jack I can use is a switched mono jack where switched port is
> tied to the tip port until a plug is inserted. My idea is to use the
> switch port to feed an out of range voltage to the tip port, probably a
> negative voltage. Then use a comparator to detect when the tip port goes
> high.
>
> Any other thoughts?
>
> --
> --Tim Ressel
> Circuit Abbey
> timr at circuitabbey.com
>
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