I have some 3V devices that seem to be operating over an analog Serial connection. Any ideas on how I can sniff out the connection b/w two devices w/ my arduino? I want to eventually be able to control them from the arduino, but I need to get the codes first.
Thanks!
You might want to try ArduinoScope: http://code.google.com/p/arduinoscope/
The Arduino sketch samples analog or digital input pins and sends the data to a Processing sketch to display. You'll find Processing familiar because the Arduino IDE is based on Processing.
That I know how to do. But how should I hookup the device lines to the arduino? Direct wiring? a transistor?
Thanks!
Depends what kind of serial protocol,
RS-232 (+-15V) or F/M-bus (+5V).
3V devices
There's a good chance they are talking at 3v levels as well, if so there's also a good chance that a 5v Arduino would read the signal correctly because 3v is over the normal threshold (.2 VCC IIRC) to be seen as a 1.
Alternatively get a clone that runs at 3v3, that will certainly work.
Or use a comparator chip.
Either way you probably should measure the signal level first, just in case there's a 232 converter chip in there somewhere. (OK that's pretty unlikely, just being on the safe side. If you use a comparator running off VIN (~12v) it won't matter).
Rob
Take a look at the signals Baum.
There's another sound card scope called Virtual Analyzer that works nice, free download from here, make yourself a set of probes using a 1/8"/3.5mm stereo plug.
If you're gonna be doing a lot of arduinoing, then a good scope can't hurt.
I use the USB scope from www.dpscope.com. $70 plus $9.50 shipping in the US, with probes too.
So these two devices each have 3 pins. One is ground, one is power (3V from CR2032) and the other is ?data? My multimeter, when connected to ground, reads an analog serial signal between 150mV and 450 mV. I have no need for a scope, really. I just want to listen and record the communication between the devices.
Thanks!
My multimeter, when connected to ground, reads an analog serial signal between 150mV and 450 mV.
The DVM is averaging the voltage on the line and the average varies according to the make up of the data. So I'd say that's ok and you have a 3v signal.
I'd just try hooking directly to an Arduino pin and use Software Serial to try reading. Echo what you read to the PC and keep changing settings until it makes sense.
Hopefully the data isn't a constant stream and you will be able to sync on it.
The good thing about having a scope or LA is that you can see the waveform and that removes some or even all of the variables.
Rob