Thread: New Project: Linux ODB-II SBC

You probably don't need that kind of power (the SBC) to do OBD2 display. This is made for Subarus but it does read OBD2 (as well as Subaru Select Protocol), and there really isn't that much to it.

Know about anything for OBDII to USB?

Originally Posted by SiGmA_X

Know about anything for OBDII to USB?

Like this?, it includes software, I don't how much just the cable is.

Hmm I like that think made for scoobs... but I'd like mine to do logging, etc and then be able to dump it off of the unit easily... thats why I would use the CF

It's supposed to do logging in future versions. It has a small chip that you change out to update the version. Plus it has a strip on the back of it that has outputs for shift lights, water injection, etc. as well as inputs for other gauges not supported by the factory ECU. There is a big strip of outputs that are unused at this time that are supposed to be used for logging. Right now if I want to log I use this.

techm3: You should consider using a small microprocessor like the BasicX for your project. You would need a protocol converter to convert OBD-II into RS232. The BasicX is more then capable of controlling a few buttons and displaying some info on an LCD. If you have programmed in Visual Basic before then it’s not too hard to program the chip. www.basicx.com

VB, C, C++, JAVA it all works for me

I'm working on a Linux car computer, too, and intend to work an OBDII interface in later, so I'm very interested in your project. I'm writing my project in Perl, so naturally I hope you choose to, too. (It's quite C-like!)

Do you intend to leverage FreeDiag (http://sourceforge.net/projects/freediag/), ScanTool (http://sourceforge.net/projects/scantool/), or any other projects?

Have you chosen OBD-II interface hardware?

I have made such a device, its powered by a AM186ED microcontroller, using a full demo board so its got two built in serial ports, some flashrom for saving the embedde software on it etc. Anyways i did the entire project my self using this board and a 320x200 pixel SED1330 controlled monocrome graphics display. It currently only works with the ISO9141-2 hardware standard(almost all JAP spec cars, ie Nissan, Subaru, Toyota, etc). The ISO standard is really easy to design the hardware for because its basicly a serial link with slightly modified logic leves. Instead of the -6to-30V for a logic 1 on RS232A its +12V, and instead of +6to+30V for a logic 0 on RS232A its 0V. This is easy to convert and because you really need to optically isolate the connection anyways you can use the optoisolators to do the level shift and inversion for you. I would recomend purchaseing the ISO 9141-2 document if you are really serious. You are also gona need to learn the iirc. SAE J1978 OBDII protocal to use for communication. Basicly the SAE protocal is used ontop of the given hardware levels, ie ISO 9141-2, PWM, or VPW. Also in the very near future there will be a new standard called CAN. I would also recoment you purchase the SAE J1978 document. Both can be downloaded in PDF format for around $40 us iirc. Again this is only for ISO specific cars, so this will not work in Fords etc. I have not designed the hardware for the two other standards so im not sure how it could be done. BTW may i suggest the MAX232A chip to do your line level conversion *hint hint* if your just gona use the PC serial hardware.
Okay that was long and prob very confusing, sorry i have a hard time organiseing my thoughts on matters such as these. Anyways i wouldn't mind helping much as i am going to be porting my software to win32 soon i think so i can so a very similar thing for my Subaru WRX, its going to be a 2x16 CHAR lcd to display things such as Engine Load, EGT Temps, Coolent Temps, Boost levels(not sure if this is possible yet), etc. Good luck and i hope what i wrote was understandable.

EDIT:
Side note, if you going to be using a PIC controller or BAISC stamp type microcontroller, you had better have a dedicated CHIP to do the house keeping on the OBDII connection. You will have a VERY hard time trying to get the BAISC or PIC controller to keep on top of the strict timing requirements for OBDII. If you do decided to go this route there are IC's such as a few made by ELM that will do all the raw OBDII communication stuff for you. You can find more info on the forums at www.obdii.com.