SERIN in acii, hex, decimal?

[sccoupe]

Ok, with your help and a little from the data sheet , I ordered some 3 pin resonators at 8mhz and they work fine. Everything works at 9600 baud and all. I hook this project up to my car (ignition on, engine not running) and it works as it should. When I start the car, the display goes crazy with all kinds of numbers. This is what happened when I tried reading an analog voltage using a picaxe. It worked fine on the bench, but didnt work with a running car. I even tried a battery for power and only hooked up the serial line and a ground. Can a schmit trigger be used on a serial line? I can only think that there is too much noise on the line. I can hook that line up to hyperterminal though and it works fine. Any thoughts?

Jason

[Archangel]

Ok, with your help and a little from the data sheet , I ordered some 3 pin resonators at 8mhz and they work fine. Everything works at 9600 baud and all. I hook this project up to my car (ignition on, engine not running) and it works as it should. When I start the car, the display goes crazy with all kinds of numbers. This is what happened when I tried reading an analog voltage using a picaxe. It worked fine on the bench, but didnt work with a running car. I even tried a battery for power and only hooked up the serial line and a ground. Can a schmit trigger be used on a serial line? I can only think that there is too much noise on the line. I can hook that line up to hyperterminal though and it works fine. Any thoughts?

Jason

Thinking out loud . . . serial data is a train of 5v pulses, so I would try putting a small value capacitor across the serial input line and bypass the power bus at the PIC too, it may help to shield the circuit in a grounded metal box too - automotive can make tons of RF especially from the ignition system. Even worse if you have a defective ignition wire as you might have 60000 volts going nowhere. A small value choke in series with the input might help too.

[sccoupe]

I just got this thing working. The interference that I was looking for wasnt there. I hooked up the scope looking for noise and realized that I wasnt looking at a TTL signal. After some research on how exactly rs232 works, I found that a Max232 chip was required for the conversion, luckily a guy at work had one. So, Im going to order some 16F688's so that the built in uart and internal 8mhz crystal minimize my components and get the job done.