I am trying to reverse engineer an ultrasonic car reversing warning system. The microcontroller on the board is pin compatible with a PIC16F1847 and so substituting a PIC would allow me to customise the functions available.

The board has a quad op-amp and well as a dual four channel analogue mux/demux and the processor. The board is double sided with surface mount components so tracing the tracks is not trivial. Also I don't entirely know what circuitry to expect. I have looked at the waveforms on the processor and it is most unclear just what the processor is doing so tracing out the circuit is necessary for understanding it.

I don't think it would be sensible to actually draw a schematic as I go along as it could get exceedingly messy. Does anyone have a good method of recording partial results which can eventually be combined into a full schematic.

 

hi
I use the camera on my mobile phone, upload to PC as required.
E

 

I sketch out a rat's- nest on paper, in pencil, then tidy up into a more logical layout later.

 

Reverse engineering a reversing warning system?

 

I'm going to make a continuity tester. The multimeter has a continuity buzzer but it's rather slow and is generous about what 'conductivity' is.
I'm following this design https://www.electroschematics.com/9232/continuity-tester-differentiates-resistance/
but replacing the green LED with an active buzzer. Actually, I'll probably drive the buzzer with the other half of the LM358 to avoid upsetting the measurement.