PID common short names

**chunkyks** · 09-20-2009, 11:55 PM

Evening all,

I've added code to obdgpslogger so that the PIDs it logs are modifiable at launchtime.
Currently it only works through a config file, or at compile time [not command-line yet]

Code:

man 5 dot-obdgpslogger

The remaining bit that I need to do is to go through obdservicecommands.h and rename db_column from NULL to a useful short column name. Things like "vss" for vehicle speed.

I wouldn't have come up with "vss" myself, but everyone else appears to be familiar with it; it seems to me that there's a common source for names of these things, but I don't know what that source might be.

Can anyone please point me in the appropriate direction for short_version nomenclature for PIDs?

Thanks,
Gary (-;

**malcom2073** · 09-21-2009, 04:47 AM

VSS is actually vehicle speed sensor iirc, which is why that's used for that particular PID. Unfortunately the nomenclature comes more from the mechanics side than the OBD side, MAF, MAP, TPS, LV8 (I never understood this one), all abbreviations for the sensors the values represent.

**Rooster** · 09-21-2009, 12:45 PM

I am struggling with the same issue. My application uses a 128x64 graphic LCD for displaying data so there is limited space for labels.

Some tags I have been using are:
IAT - intake air temp
AMBT - ambient air temp
O2S1B1 - O2 sensor 1 bank 1
O2S2B1 - O2 sensor 2 bank 2
ADVNC - timing advance
TPS - throttle position sensor

When you make your own tags it is easy for you to know what they mean because you made them. But I wonder if anyone else will know what I mean.

An 'unofficial' standard for short tags would be nice indeed.

**chunkyks** · 09-21-2009, 12:54 PM

I have been informed off-forum [thanks Graham!] thus:

The short names are just the abbreviations you see in your copy of SAE 1979
under the column External test equipment. Perfect for a db_column name.

Now if only I can find my copy of 1979, then I'll be set. I *think* that it's *somewhere* in my garage - we haven't really begun unpacking since we moved in :-(

Gary (-;

**chunkyks** · 09-21-2009, 10:09 PM

Yep. Garage it was.
obdservicecommands.h. Now obdgpslogger's columns-to-log are run-time configurable.

Reading my spec, I found that the spec contains info on PIDs up to hex eighty-something, but the only online references go up to about 0x52. Can anyone point me to an already-published online reference for these higher PIDs? J1979 is kind of a proprietary spec, publishing stuff from it almost verbatim [in a big struct] wouldn't be my best idea.

Gary (-;

**justchat_1** · 09-21-2009, 10:21 PM

Any chance you have a copy of the spec in PDF form?

**chunkyks** · 09-21-2009, 11:23 PM

Sorry, I sprang for the dead tree flavor because the PDF version carries DRM burdens that will not work for me [such as requiring a separate, windows-only, proprietary plugin to view]. Then there's some limits on what you can do with it [such as number of prints, or simple things like viewing while not connected to teh intertubes].

For that matter, even if I had the PDF version, I'd be unwilling to hand it around; respect of copyright is pretty central to the whole world of open source, even if there are occasional ridiculous copyright laws.

Gary (-;

PS **** DRM. Congratulations, assholes, you managed to make the electronic version *less* useful that the dead tree flavor. It boggles my mind that that's even possible.

</tirade>

**justchat_1** · 09-22-2009, 12:26 AM

Originally Posted by chunkyks

Sorry, I sprang for the dead tree flavor because the PDF version carries DRM burdens that will not work for me [such as requiring a separate, windows-only, proprietary plugin to view]. Then there's some limits on what you can do with it [such as number of prints, or simple things like viewing while not connected to teh intertubes].

For that matter, even if I had the PDF version, I'd be unwilling to hand it around; respect of copyright is pretty central to the whole world of open source, even if there are occasional ridiculous copyright laws.

Gary (-;

PS **** DRM. Congratulations, assholes, you managed to make the electronic version *less* useful that the dead tree flavor. It boggles my mind that that's even possible.

</tirade>

I was thinking more along the lines of if i had a sample or two of what was "undocumented" then it would be a lot easier to find the sources where it is documented. Along those lines anything that can be reverse engineered is fair game - as long as its not done using their specs.

Would you mind posting a PID or two (just the code) and i'll see where they're defined. That shouldn't be a problem since your not posting descriptions.

**billmarkviii** · 10-11-2010, 12:59 PM

Originally Posted by chunkyks

PS **** DRM. Congratulations, assholes, you managed to make the electronic version *less* useful that the dead tree flavor. It boggles my mind that that's even possible.

</tirade>

Most larger libraries will have a physical copy of the SAE technical Handbook. It has not just J1979 but every current standard applicable at the time of publication ( with a few left out to confuse and frustrate you ).

The library will even direct you to their photocopier.

From The Copyright Act at 17 USC S 108:
Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specified conditions is that the photocopy or reproduction is not to be "used for any purpose other than private study, scholarship, or research. " If a user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of "fair use," that user may be liable for copyright infringement.

From the DMCA:
(f) Reverse Engineering. — (1) Notwithstanding the provisions of subsection (a)(1)(A), a person who has lawfully obtained the right to use a copy of a computer program may circumvent a technological measure that effectively controls access to a particular portion of that program for the sole purpose of identifying and analyzing those elements of the program that are necessary to achieve interoperability of an independently created computer program with other programs, and that have not previously been readily available to the person engaging in the circumvention, to the extent any such acts of identification and analysis do not constitute infringement under this title.

(2) Notwithstanding the provisions of subsections (a)(2) and (b), a person may develop and employ technological means to circumvent a technological measure, or to circumvent protection afforded by a technological measure, in order to enable the identification and analysis under paragraph (1), or for the purpose of enabling interoperability of an independently created computer program with other programs, if such means are necessary to achieve such interoperability, to the extent that doing so does not constitute infringement under this title.

(3) The information acquired through the acts permitted under paragraph (1), and the means permitted under paragraph (2), may be made available to others if the person referred to in paragraph (1) or (2), as the case may be, provides such information or means solely for the purpose of enabling interoperability of an independently created computer program with other programs, and to the extent that doing so does not constitute infringement under this title or violate applicable law other than this section.

(4) For purposes of this subsection, the term “interoperability” means the ability of computer programs to exchange information, and of such programs mutually to use the information which has been exchanged.

**billmarkviii** · 10-13-2010, 07:34 PM

Originally Posted by chunkyks

J1979 is kind of a proprietary spec, publishing stuff from it almost verbatim [in a big struct] wouldn't be my best idea.

Gary (-;

Interesting thought but in my opinion wrong on 2 factors.

1: Being a federally mandated specification it should be available to the public at a nominal cost ( not a profit, actual cost to deliver ) in order for a citizen to determine for themselves how to comply with the law. This issue comes up when cities adopt the commercially available building codes as their local codes and to my knowledge has yet to be taken to a high enough court to set precedent.

2: Although the idea that the number 69 may refer to either an intimate act or the hexadecimal representation of some particular value in a system may be somewhat original only one particular representation of it is copyrightable. In other words, look at it like a phone number. See Feist v. Rural for US law copyright implications of this. Australian and European citations come up in the same manner and same direction. A collection of facts cannot be copyrighted, only a particular creative expression of them.

You would be fine publishing a 'C' structure including the facts contained withing the J1979 specification publicly.

And, as a matter of law, including that information in a program or in print is fundamentally similar although interestingly, for matters of export law there are different rules. See the EFF's printing of the source code for the encryption algorithms in book and T-Shirt form to circumvent legally US export controls on cryptography.

Companies often threaten independent tinkerers ( formerly known as hackers although that term has been hijacked ) with copyright and now DMCA. A bit of study in copyright law tells us that most of these threats are baseless and may even be grounds for counter-suit under various laws restricting baseless threat of lawsuit.