1997 F-Body Tools

[kur4o]

Interesting stuff Tom. I recently bought a 2001 Y body and was thinking to myself how cool it would be to have an open source tool to talk to it with. But for now I'll be dusting off my Jet cable / software (based on tunercat).

Just to clarify a few bits - the arduino IDE is not sanctioned by Atmel. They also have a free but non-open IDE suite for their AVR products but it's not quite as friendly to beginners.

A little off topic but 2001 ybody pcm is currently very well hacked, with freeware support. Still a homebrew cheap cable is missing, but you can easily fill the gap.
Maybe a new thread will be more appropriate to get you started.

On topic, the progress is awesome. Great work and complete write up. Can`t wait to see that project finished.

[Tom H]

I received mail with a few questions regarding the home brew J1850 cable. For this project I have built a single prototype and the software is still somewhat in flux. Having said that, it works reliably and I have been looking at extending the upload capability to the Eside. I am answering questions on this thread because whatever someone finds unclear, others will surely question as well. OK so....

J1850_IF.jpg

1) The 820 Ohm Resistor; is that a commonly available discrete or should I combine a few resistors to get that value?
This resistor was selected based on several assumptions. The zener diode is 8.2V and for my test setup the input voltage is 12V (give or take). These two components are just there to provide an 8.2V source for the line driver. There should be round about 4v across the resistor. This gives us about 5ma of bias current for the zener. Since IZT of the zener is 30ma you could go with a much smaller resistance but not too much larger. Probably 1K would be fine. Just depends on what you have floating around your tool box. I suggest you use no larger than 1K or smaller than 500 ohms. With these values resistor of 1/10 watt will be fine. This part is not sensitive... use what you got.

2) Best to get the 47K resistor in the bulk pack kit?
The 47K resistor forms a voltage divisor with the 10K. The ratio of these two parts is important but values could be changes. These two resistors along with the transistor and another 10K form an inverter and a level shifter/buffer. Test your circuit by sending frames. You should see the output of this inverter toggle and the circuit will send your sent frame such that you can monitor it for correctness on your terminal. These resistor are all available on digi-key/Amazon/Ebay and hundreds of places.

3) The Arduino_Nano... there's a lot of choices on SparkFun.com. Any recommendations in particular? I see this one: Arduino Nano Every - DEV-15590 - SparkFun Electronics
I bought several Arduino boards. I like the ones that come with a short cable and have all the header pins installed. I can't recommend a vendor except to say that some things are in short supply just now. I got mine through Amazon and found a vendor that had a good delivery and good recommendations from other buyers.

4) Any particular size breadboard you recommend?
I guess it depends on your skill soldering and so on. If you want small, surface mount resistors are good. you can use wirewrap wire to hook things up. With leaded components you will be a bit larger due to the resistor wires and bending them to fit the holes. I would thing 2" by 4" would be more than enough. So far I have not built a breadboard. I built mine in a prototyping strip... this is just another project I need to complete.


Hope this helps.

-Tom