DIYEFI.org Forum

Yup, I'm just about ready to post my schematic for a USB-to-RS-422 adapter over in the general hardware section.

Sounds like something Bosch does in their ECUs. The Motronic 2.9 in my 1998 Jetta had short/long-term "fuel trim" to compensate for bad MAF/O2, based on what people said. Have a short-term for say.. each time the car was on, and then average it into the long-term I guess.

For VWs, there is really only stuff for the turbo variants of mark 4/5 cars (1999 and up). You have options like REVO, Unitronic, GIAC. These companies have "power programmer" style hand-held ECU flashers. The thing with these companies is, though, they only tune VAG family cars, and they ...

It's sorta cool, but not really. It just means they figured out all the cars they can reprogram stuff in from the OBD-II port. Their product is not doing anything special compared VAG-COM for Volkswagens, for instance. Even then, they are a generic company trying to support a myriad of different car...

Well I can see what your concerns are. You're right, the existing way should let the receiver know where they are during a packet, not between it. My way would be periodic. Both of our ways are still prone to noise as far as I can see. The existing way just gives the receiver a chance to resync fast...

Well, do you have a link to the theory behind this escaping scheme? I only understand it as start/stop markers. You make it sound like it's a set of bytes injected every so often in a packet. It is quite simple :-) If you are going to have start and stop markers then you can't let them appear in th...

One of the design requirements from the outset of this serial side show was to be able to operate in a horrendously noisy environment or with bad hardware (both very common IRL) with only a drop in performance or a failure to operate at all. Spurious data that could still make it in with the barkin...

Hmmm, do you mean a sync code like a barker code? I know those are common place in low bandwith noisy radio enviroments. http://en.wikipedia.org/wiki/Barker_code Looking at the wiki page, I'd say that a barker code is pretty much analogous to my idea of a "sync" code. The barker code look...

You're still missing Fred's point. There is a mode where the ECU is sending data log packets continuously without the PC constantly asking for it. In that case, it is possible for the PC to be connected to the ECU while the ECU is already sending data. With the start/stop bytes, it is possible to s...

If you want to talk pure bandwidth savings, it's going to be no different using a size field in the header than a start/stop byte. If I'm not mistaken, the talk on the start/stop stuff I've seen has hinted as possibly more than 2 bytes total to delimit a single payload. Then, the size field is savin...