The MegaSquirt Project has experienced explosive growth other the years, with hundreds of new MS installations occurring every week - a phenomenal success! MegaSquirt has been successfully used in all aspects of Internal Combustion engine applications including R&D, Industry, Race, and Research. The MS project has transformed itself from a simple R&D project into a full-featured mature engine control system. To reflect this the support structure has also changed to meet the needs of MegaSquirt Users.
Moving forward, the R&D forums for MegaSquirt project are in a read-only mode - no new forum posts are accepted.
However the forums will remain available for view, they still contain a wealth of information on how MegaSquirt works, how it is installed and used. Feel free to search the forums for information, facts, and overview.While the R&D forum traffic has slowed in recent years, this is not at all a reflection of Megasquirt users, which continue to grow year after year. What has changed is that the method of MegaSquirt support today has rapidly moved to Facebook, this is where the vast majority of interaction is happening now. For those not on Facebook the msextra forums is another place for product support. Finally, for product selection assistance, all of the MegaSquirt vendors are there to help you select a system, along with all of the required pieces to make it complete.
A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
Hi,
I just wanted to share some of my GPIO build that may be useful. Currently the system is stable and working well in my daily driver thanks to Lance and other forum member's help!
1) Dealing with the VSS signal has given us all fits in one form or another. My solution was to simply use a factory GM DRAC to deal with the raw VSS\OSS signal, then dump the square wave output into the GPIO thru a simple voltage divider with a 5v Zener diode as a voltage limit clamp for safety. I mounted the unit inside the GPIO enclosure. Just about any year DRAC (or VSS Buffer) will work as they all put out a nice square wave. The early one I have is an “open emitter” and requires a pull-up resistor. Apparently they were made from the mid 80’s to late 90’s and can be had for next to nothing in the bone yard
2) The 4.7 ohm PC resistor needed a solid, safe home since I didn’t want it floating around in the harness. I simply mounted it under the AMPseal connector and broke into the output trace on the GPIO board. It barely gets warm when passing maximum current and stays cool during driving.
Rob
Attachments
(Image from internet search)
GM DRAC early.JPG (36.15 KiB) Viewed 13141 times
GPIO_PC RESISTOR_rxl158.jpg (154.04 KiB) Viewed 13141 times
GPIO_GM DRAC VSS_rxl158.jpg (244.26 KiB) Viewed 13141 times
Very nice! The DRAC ("Digital Ratio Adapter Controller" found in many GM vehicles from 1992+) are a nice find. In addition to providing a nice square wave output, they also slow the signal frequency considerably (a typical result would be a VSS input of 96000 pulse/mile, and a DRAC output of 2002 pulses/mile), resulting in less interrupt overhead in the code from handling the VSS signal. There is more information on these here: http://614streets.com/drac.html
Thanks for posting this info!
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Just spent some time fixing my vss using a nte 995 sine wave to square wave converter. It was a bit of a fight due to noise but it works. It's almost the same as a lm 2907 chip.
I am glad you were able to make something that works for you. VSS noise is such a pain for so many users. In theory these speed signals are always perfect, but in reality they never are. And when you have a 'zero-crossing detector' sensitive to voltage swings near ground, even low levels of noise cause problems. I am happy you will now be able to leave these problem behind!
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
