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Got a technical problem? Can't understand a piece of jargon or some technical principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097 or send an email to silicon@siliconchip.com.au

OBDII interpreter for pre-2006 Commodores

I have just completed building the OBDII Interpreter, as designed by John Clarke (SILICON CHIP, February 2010). So far I have not had the opportunity to test it to any great extent.

My present main use hopefully will be to use it with pre-2006 Holden Commodores with their Assembly Line Diagnostic Link (ALDL) protocol. Several of the later models use the common 16-pin OBD connector although the data access is by pin 9, easily linked across to pin 10.

My study of the circuitry in conjunction with info from various web sites would indicate to me that pin 10 is the negative line j1850 of the VPW (in) protocol and may be suitable, perhaps with some modification, for the reception of data from the Commodore VN, VS, VT etc models prior to 2006. Apparently this data requires inversion and translation to RS232 levels with the MAX232. All this is catered for in your design. Software is available from several sites I am informed, together with some fairly basic circuitry.

However, with Mr Clarke’s extensive knowledge and experience in this field, would it not be possible to extend the uses of this project to include advice on using it with the very large number of Holden models that have the ALDL diagnostic system?

I have read and enjoyed many articles over several years in “Electronic Projects for Cars” and “Performance Electronics for Cars”, etc and have learnt much about modern car electronics to add to my knowledge base. I have no doubt that additional information would enable further use of the OBDII Interpreter to cater for any car which uses an ECU to control functions and diagnose fault conditions. All we need is the ability to connect and translate as required. (T. C., Bendigo, Vic).

• The OBDII Interpreter was designed specifically for the OBDII protocol used on 2006 and later vehicles.

Before 2006, there was a huge range of on-board diagnostics techniques on cars and virtually a different format for each vehicle manufacturer and model. The Holdens did use the ALDL protocol and we did direct readers to a website for this in the general OBDII article published in the same issue (February 2010).

The problem with describing a project for pre-OBDII cars is that there are so many variations in the protocols used at that time that while it may operate on one model it is unlikely to work on another.

DAB+ Digital Set-Top Box: Add-On For AM/FM Radios

I am writing to ask whether the hardware etc might be available for the production of a “DAB+ digital set-top box” for the reception of DAB+ digital radio on existing AM/FM receivers? Before you discount this out of hand, may I sketch out how I see such a STB working.

The box would contain a digital receiver/tuner and scanning circuit to “load” and store the digital channels. However, instead of the cable link that is used between an HD or SD digital STB for TV reception (ie DVB+), the box would include a short-range transmitter than could be
user-tuned to a specific unused AM or FM channel, the AM or FM band also being user selectable, so that all of the radios in the household, within say 10m of the DAB+ STB can tune into the currently selected channel. Channel selection could be via a remote control but with buttons of the box that can also be used to perform the same functions.

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