I have a small project where I am sort of reverse engineering the old Apexi SAFC fuel controller for fuel injected cars. Its more of just curiosity in the sense of @ 3k RPM with a setting of +3 how much does the Apexi adjust the incoming signal.
So the Apexi can read several sources including RPM, Map, TPS, Hot Wire, Flap which are mostly 0-5v but can be up to 12volt.
The project is very temporary since this only needs to be done once, that is why I am interested in something simple and cheap as long as its accurate.
The way the project is setup is I use 1 analog output which scales from 0-5 volt and that loops back into the micro for a reading, this reading is sent via serial to a PC to later be parsed.
The other output from the same pin goes through the Apexi SAFC and back into the micro which is then sent via serial to the PC.
I also have a hard drive with 4 magnets and a magnetic pickup which simulates RPM, I use 4 magnets so I can get a simulated 8k RPM when the drive is spinning at 2k. I adjust the speed of the drive with external 12volt source controlled by the micro which it reads the rpm and then sends it to the PC via serial.
Both of these readings are compared in Excel with a nice Line graph showing the difference at 0-5v in 255 increments over 0-8000 RPM.
I know most of the signals the Apexi reads are 5 volt but I know some are 12 volt so I was just getting a game plan in place for reading a 12 volt signal.
Once I am done with the project I will share the results on my website but I currently have no desire to re-make the Apexi SAFC since I already own one