Hi,

I hope you don't mind me emailing you, but I wondered if you would mind assisting me / pointing me in the right direction with a few questions regarding OBD2?

First of all I know I can buy tools to do OBD2 interfacing but I would quite like to learn to do it myself, and although there is a lot of resources on the internet I don't know how much of it is relevant / true.

I have a 2006 Vauxhall / Opel Astra which has no temperature gauge as in their wisdom decided to leave it off! So I wanted to build my own with a 7 seg or LCD display. My girlfriend has a 2009 Toyota Auris and I want to interface with the CAN bus to make the doors automatically lock above a certain speed and unlock when the ignition is off.

Of course, the easiest way to develop would be with a simulator, which would be ideal for commercial stuff, but I don't want to spend a fortune on simulators which are closed / proprietary just for something at a hobby level.

I came across your page and hoped from the name there would be something free to download / build and use, but I can't see anything available for free so I am guessing you have not released any of the OBD2 stuff as free?

My questions are as follows:
1. What kind of hardware do you use in your simulator and interface dongle? i.e. do you use the Elm327 for example?
2. What would I need to do to build a simulator? Is it the reverse of the dongle, by that I mean writing the responses rather than the requests on a bi-directional bus?
3. I understand there is several protocols, VPW, PWM, K+L Line and CAN Bus, The CAN hardware looks fairly straight forward with a Microchip BUS transceiver and PHY, but what is required for the other protocols?
4. Are the request codes the same? Wikipedia just lists that you can send PID's as bytes such as 010D, is this it or do you need to add some more bytes before to do some kind of handshaking?
5. Is there any site / document that fully defines (correctly) the OBD2 protocol?
6. Am I over simplifying it by assuming that once the hardware interfaces are done and programmed that the code to handle the PID's and DTC's are identical?

I understand that you may want to keep the information close to your chest as no doubt you have spend a lot of time producing something that works, but any assistance / help / guidance would be greatly appreciated!

Kind Regards