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Hello All first post! Open Source questions and such
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Post Hello All first post! Open Source questions and such 
Okay so I have come here because all the links for information on MegaSpark and MegaJolt seem to end up here. I am specificaly looking for MegaSpark information, schemantics and firmware. I like the MegaJolt, but I want to run distributer based ignition on a VW Hall type setup. I am VERY familiar with MegaSquirt's themsleves having built DOZENS of them and countless installs, but am looking to expand my electronics skills. Looking to learn about PCB making and processor burning and programing.

I think a small ignition module style project that gives me simple ignition programing and hooks right up to the VW setup would be the coolest. And probally cost less than a replacment ignition module... I have an old '77 rabbit I want to play with in "OE configuration" before I go full MegaSquirt conversion on it.

Anyways I can't find schemantics for either MegaJolt or MegaSpark ANYWHERE and was hoping for some guidance here...

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Hello,

I agree that would be a great learning project to work on! We are also looking at developing a very cost-effective, distributor-only controller, we feel it would be a good compliment to our existing offerings.

However, when I google 'Megaspark' the first link points here:
http://home.comcast.net/~tjhafner/MegaSpark.html

Did this information yield anything helpful?


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brentp wrote:
Did this information yield anything helpful?


I had found that also but didn't walk away with anything from it. Seems that MegaSpark, unlike MegaJolt, is based off the pre-existing v2.2 MS platform. Simple enough to cut out and rebuild just the neccisary circuits... But... I have one of Pat Carlier's MegaProgramers with the KX8/QT4 adaptor and wanted to play. It seems to me a more intelligant aproach would be to use the 68HC908KX8 used in MegaJolt in a smaller package designed just for this purpose. Looking over the applications and hardware used by autosport labs, I think the software interface used here is probally better than a customized MegaTune derivitive. Although larger maps would be nice... Is that even possible on the 68HC908KX8 architecture?

I am very familiar with the setup and modification of V2.2 and V3.0 MegaSquirts for rock steady and reliable hall ignition control as used by Bosch on the VW's (and many other cars). In building a new unit I would add a few things. First IF using the bosch ignition module more dwell options are needed. The Bosch modle needs to see 60% dwell. An option not avalible in the MsnSe code. But I think I would actualy do away compleatly with the ignition module and let the "MegaSpark" control this directly. The primary load signal would likely be the MAP. I can't really see any advantage to TPS input if not running fuel... Other than for datalogging. IAT would be usefull for engine temp.

Really I think the big question here s how far to take the platform, or platforms being thought about for development. I can modify either a V2.2 or a V3.0 ECU very quickly for a simple Hall ignition. But for more complex decoder ignitions the V2.2 hardware isn't capable. And the V3.0 requires unreliable fiddling much of the time to get working properly. So if a more flxible solution is required then a circuit based aroud the lm1515 (I beleive) would be a more appropiate thought. Problem is I suspect that this is going to take a processor more capable than the 68HC908KX8?

1) Okay lets start off easy. How differant is the code in a MegaJolt processor from say the MsnSe code? Is the 68HC908KX8 even capable of running a more feature rich code with expanded maps?

2) Then I prefer your software at a glance to MegaTune. Keeps things "neatly seperated" but perhaps it would be nice to be able to read datalogs with MegaLogViewer.

3) Are you thinking a single platform capable of all types of distributer ignition setups? I beleive theHall setup is simpler than a VR or reluctor type, but probally not by a lot. Likely both coul be built into one unit.

4) Or even distributer based and wheel decoder? Honestly if I had to fall back on a wheel decodr type, I would make a seperate ECU for this. Unless the LM1515 based setup will work for both. A firmware change would probally be simpler than a more complex software solution with all the options already codd into th processor.

Well whatever the case, I would be highly interested in a distributer based setup option and am more than willing to help with developing it.

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To keep things simple on a distributor based ignition system it would be helpful to limit capability to 'one pulse per cylinder" - so one tooth per cylinder on a VR sensor configuration, for example. Support for distributors having more fine grained wheels would be out of scope, at least initially.

On the V4 controller the KX8 processor has been replaced with a QB8 processor- similar, with just a bit more RAM. V4 was mostly a port from the V3 code, but ended up being quite a bit more work due to subtle hardware differences.

However, from my recent work on RaceCapture and Megajolt2 I've been very pleased (and spoiled) with the processing power, capacity and flexibility gained by using an ARM processor. While it may seem overkill for this application, it isn't overkill when it comes to price, as many ARM implementations have been developed to compete directly with 8 bit micros!

For anything but the most trivial devices, my approach is to choose the ARM and find a reason to disqualify it. Lately, many engineering trade journals have been predicting 8 and 16 bit micros going by the wayside in preference for 32 bit architectures, except for areas like ultra-low power applications. I agree in principal, but I think their timeline projections are exaggerated as the inertia behind existing, established technologies like PIC and AVR is very significant.

For #2, I agree, thanks! Smile This software will be the starting point for future ignition controller projects (and is the foundation for the RaceCapture PC software)

For #3, Yes, it should be possible to support multiple platforms without adding much cost. It's always a tough balance to decide how much to saddle people with features they won't use, but must buy; e.g. MAP vs. TPS optioned MJLJ V4's.

Unfortunately, NatSemi has obsoleted the through-hole version of the LM1815. For dedicated VR amplifiers it seems only SMT versions are available and they are not very hobbyist-friendly. I would still prefer a dedicated chip to discrete components- benefiting from simplicity and leveraging the body of development/testing work behind it. That leaves the crusty-old but reliable SMT LM1815 and a much newer chip by Maxim (don't have the part # handy).

Worth mentioning- and it begs a larger discussion- the roadmap is:

Megajolt2 - next gen equivalent for 4,6,8 cylinder MJLJ + EDIS
Megajolt/COP - As above, but designed to work with coil-on-plug modules having integrated drivers
Megajolt/D - what we're discussing in this thread


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