Circuit golf

not a good solution (succecptable to HF noise, common mode noise, and distortion...) but very golf.

Should be enough signal swing to illuminate an IRED so here is my idea:

Nice challenge, thanks.

piglet

Not going to get much cheaper than a single MCU for the whole stack, no?

It'll need coupling, filtering and protection, but that's fairly academic.

With a bitrate that low, you might as well acquire it with ADC and DSP the whole thing.

Even mere ATMEGAs have been made to talk USB, Ethernet and others. Recently saw an article, someone did this for an old HP two-wire serial protocol that was popular with their calculators, PCs, and some test equipment, from the

Very simple method if you don't mind that the input voltage threshold might be a bit crap. Which means, it may not be exactly production ready; but even then, calibration can often be applied at nearly no cost.

Now, I gather this is some kind of modulated RF signaling? Sampling that real-time will require a good bit of grunt (nothing a modestly priced ARM can't manage), else with some signal conditioning (PWMDAC bias + internal analog comparator) it could be detected directly (GPIO) or with the help of a timer (frequency counter or missing-pulse detector?). Generous filtering and error correction in the digital domain, and you're pretty much done.

Might not be all that quick to implement, but so what. What if someone wants a different operation mode? Back to the soldering bench all over again; whereas the MCU can just load up another code module and it's off running. ;-)

Tim

I gathered that it was the wired protocol where most of the energy is below

you make a good point, an ATTINY25 ADC takes 13 clocks to perform a conversion, so at 200kHz ADC clock would be fast enough to recveive the information although at such a low sample rate (15Khz), the DSP code will be working hard to extract timing information from blurred slopes. (processor speed is about 16MIPS with no mupliply in the ATTINY) clocked at 1 MHZ the ADC will be noiser but the edges with be clearer.

Maybe a GreenPAK would be a better choice SLG46534, three comparators,

Not really in the spirit of circuit golf (which includes "why use a million transistors when four will do?").

My objective is to get clean RS-232 to feed to a (hardware) UART, not to build a software UART.

No, it's just an encoded form of 9600 baud RS-232, superimposed on a DC supply line using alternate space encoding.

Again; circuit golf is about economical circuits you can make from recycled jelly-bean parts on a Saturday afternoon.

CH