Any interest in developing an open source fuel economy gauge/computer?

[dcb]

re: Palm, the palm has been mulled over (there's a waba and a palm thread here). I was really pushing for it early on but have changed my position. And yes, I thought much longer than I should have about a "raw" serial port connection I think I put some code in the opengauge sourceforge repository if you are curious, should have most of the building blocks for getting data from the serial port and displaying it/etc.
here it is:
http://opengauge.cvs.sourceforge.net...l%20processor/


re: OBD, cfg83 is chewing on a scantool.net adaptation: http://ecomodder.com/forum/showthrea...&highlight=pid , maybe you can combine forces if you want to get an obd solution going sooner? Let me know if you get a decent fuel consumption algorithm put together I've got an elm chip, but the more universal (and less expensive)injector and vss tap are more of a priority imho. And if someone teaches the arduino all the various obd protocols, I'd certainly be interested too.

Paul, nice to see you here I was really tempted by your serial lcd board when I was pulling my hair out over the LCD hookup

[jim-frank]

This thread excites me, as well. However, I haven't the time to learn another language, nor the money for anything more involved than a few logic chips. I just finished a VB program to interface a couple of different geiger counters to my PC and laptop via a standard serial port, so naturally that route comes to mind.

I think a pair of (really cheap) comparator chips to obtain and clean up the pulses from an injector and the VSS, a rising/falling edge detector, and then using the cleaned pulses to toggle the DSR, RI, and DTR pins on an RS232 port might work OK.

I haven't read any comments on the retro analog approach, either. Something similar to an old tachometer circuit, using a bridge to balance injector pulsewidth against vehicle speed, maybe.

I'll probably play with one or both of these approaches, myself...

This forum is really excellent.

[jksoft]

I have been following this discuss from the beginning with interest, but to this point I have not been in a position to participate. I would now like to get involved for a multitude of reasons and I just ordered my FreeDuino kit. I also ordered the 16x2 LCD.

I have extensive programming experience although none of it is with microcontrollers as well as experience building and repairing electronics.

If I can be of any help, please let me know. My first step will be putting together the kit and getting it working with the LCD.

J

01 PT Cruiser

[dcb]

Hi guys, welcome, glad you are here

re: retro, I've been referring to this lately:
http://www.circuitcellar.com/avr2004...05abstract.pdf
http://www.circuitcellar.com/avr2004/wentries/A3805.zip (10 meg)

re: help, cool! I think we are very close with the software for v1. But code/hardware reviews are welcome. Start here: http://forum.ecomodder.com/showthrea...pace-2115.html

[gamer_jim]

Great thread guys. I too am very interested in this project.

Here's a little background on me:

I've been an applications developer, mostly .Net and Java, for 7 years. I am also an Open Source advocate. I am very lucky that in my job my boss lets me choose what vendor to use and I usually go with the Open Source ones.

I don't know much about electronics so I think I will have to stay on the software side of things. Maybe I would qualify as a tester for this project. Money is really tight for us until we sell our house so the $50 in parts would be acceptable for the Arduino + LCD.

Let me know if theres anything I can do. I can purchase the board and download the latest version, but I haven't a clue as to how to wire the VSS or the injector monitor. It looks like the language the Aruino uses is not terribly hard to learn.

[LostCause]

Great work on developing the fuel gauge. Since Mark I is the basic VSS/injector MPG method, I suspect Mark II will use the OBDII protocol.

If that is the case, here is a resource that shows circuits for converting OBDII to serial. Also, the basic coding structure of all the OBDII interfaces is shown. This is above my head, but hopefully not above others.

EDIT: Probably the cheapest interface chip for OBDII -> RS232. It covers all the old protocols (ISO 9141, PWM J1850, etc.) and the new CAN bus.

- LostCause

[dcb]

If *I* were to play around with an obd version it will be elm based, and use the less expensive single protocol chips because:
1. they are less expensive
2. they are less complicated to hookup (only care about a couple obd pins, not all of them.
3. I already have a 323

Here are some schematics:
http://www.scantool.net/schematics.html

[looking at the 323 elmiso schematic] if it is connected to a duino, you can skip the rs232 stuff on the lower right , just use ttl to the duino tx/rx ports@9600, and all the blinky LEDs in the upper right and the voltage regulator circuit. So you'd be left with 8 resistors, 3 transistors, 1 crystal, 2 capacitors, 1 diode, and of course the elm323 and an obd plug, just for iso protocol.

[jmonroe]

Does the ELM use TTL straight out of the chip? I am currently trying to use a MAX233 on the Arduino side to convert the ttl to rs232 but, I am having some trouble. I thought that the chip itself used rs232 but, I hope I am wrong.

[dcb]

I don't know for sure, but typically the chips talk ttl. The extra resistors and transistor and diode make it look like rs232 in that circuit. And with an arduino right there, you can probably just use ttl @ 9600 baud (though you probably have to unhook things to program the duino).

Are you going rx to tx, tx to rx in your connection?

[jmonroe]

It looks like the RX schematic on the ELM is converting ttl to rs232 but, the TX line doesn't look like it.

I am switching tx and rx. I had it working once before. I have a pre-built ELM which I have tested with a USB to serial adapter and hyperterminal.

Also, I do have to unhook things to program the arduino