We need to lay out a basic board

[510rob]

I have found what I sought in the other thread; Fred's basic criteria for a simple, basic, low cost platform for development. I will go with that, and post results when appropriate.

[EssEss]

less need to tweak it to make it work well

c'mon man, have you actually used that chip yet ? I'm pretty sure 99% of folks on the forum never heard of it until I mentioned it. it's not the holy grail, but it's just as easy to tweak as an 1815. Seriously though, it sounds like freeEMS is overkill for your application - why doesn't ms fit your needs ? at least you'd have something more mature to tweak on if it didn't fit your criteria. I'd be willing to help you in any way that I can w/firmware and such.

as I've offered before, I have gerbers and a sch of my little test board based on the 9924 ... same as gearhead's idea (I think?). Like him, I like to break my projects down into little boards that I etch myself and piece together to converge on a final design.

testing mode a2:


my setup:


I have a bunch of driver boards and stuff, but I'm trying to move into a more final version of my ecu before springing it on the public. I don't like to throw immature stuff out there and have it picked apart without seeing the big picture first (unlike fred ). some recent project shuffles at work have seriously hampered the progression of it - so I don't know when, or ever, it'll be mature enough for my liking.

[AbeFM]

Super quick:

I really like 510's idea - if we're stuck on pin ideas, leave jumpers for the major candidates, and again, don't be shocked if it ends up in the garbage.

I would think the boards could be cheaper. My cards I had printed were, well, $120 for 11 boards or something like that. Maybe 150. I think 5-10 boards won't be a problem, and for $20, sure if I have to junk it in a few months so be it. Modular modular modular beats perfect signals hands down.


One thing you missed, though, 510 - a fair number of folks will want 6 cyl support. 8's we might be able to skip but I think without 6's... Will it hurt us?

Certainly DB's, and I like the idea of a short board stack for different features - one of the main advantages: If things change, don't use a connector, solder in wires and you can cross signals easily.

BTW - on my little board, I stole Jean's trick of putting jumpers in, and the great thing is I can run my MS on the jimstim in part or in whole, even while plugged into the car:

I just lift a jumper and run a wire to the stim. Works well and lets me keep an eye on things.

Shoot, I had more thoughts but have to run. More later.

[jharvey]

c'mon man, have you actually used that chip yet ? I'm pretty sure 99% of folks on the forum never heard of it until I mentioned it. it's not the holy grail, but it's just as easy to tweak as an 1815.

Agreed, the max chips are not the holy grail, but certainly do have a lot of nice features that aren't offered by the 1815. As far as I can tell, it typically doesn't require tweaking. I certainly think those max chips are better than the 1815, and I feel it's the better chip to use in the board I've been laying out. Thanks for pointing it out, collaboration and community team effort at it's finest as far as I'm concerned. I don't think I originated any of the parts on the board, simply drew up what other people have mentioned.

I have the 9927 on hand.

Seriously though, it sounds like freeEMS is overkill for your application - why doesn't ms fit your needs ? at least you'd have something more mature to tweak on if it didn't fit your criteria. I'd be willing to help you in any way that I can w/firmware and such.

[drama alert]
The short version, I received the MSII V3.0 with JimStim, ect as a gift from a variety of birthday and xmas gifts from family members. My first goal is a small engine because it's budget friendly, as well I want to do some experimental stuff. I can't get many of the sensors like you can when you use a vehicle engine, many I have to build myself. When I posted about hardware design in MSEFI land (specifically the thermistor), I apparently broke the hardware rules, and was banned from all MS sites. I don't think that's right. Claim to be open, then specifically target people and ban them from reading the content. Search the MS forums for my name jharvey. Last I checked you won't find any posts from me at MSEFI (some posts made it at MSEXTRA, but most were deleted or removed), so you can't make a judgment yourself if what I said was right or wrong. I suspect most people wouldn't object to what I had inquired about. However my inquiry did surface some of their measurements inaccuracies, so from the stand point where they have product they are trying to sell, it makes sense I was banned. It's hard to sell product with known issues at the hardware level. Therefore I have a chip on my shoulder about MS, and I prefer to participate in a truly open project. I really need access to the nitty gritty that I can't get in MS land.
[/drama alert]

Thanks for the offer to help set it up. However, I'm not in a rush, and I have no plans to make it a MS project. I'm willing to wait for FreeEMS to mature, and I'm willing to offer contributions to help it mature. If all goes well, after I'm happy with how it performs on the small engine, there is a good chance I'll upgrade my little red suby.

Relative to hardware, on my project engine, I have a hall setup, so I won't need the VR stuff. I should be able to interface this chip directly to the CPU. My wires are short, and not confined like when under the hood or bonnet, so RF should be minimal to begin with. The hall should be able to drive my signal hard so it should have a very nice SNR. The other place I might have some trouble is with the thermistor for intake air temp. I was planning to simply hang the sensor in the air, so no thermal mass to help dampen the signal. I'm a bit concerned about the self heating effects in this configuration. I should be fine for the air temps when the ambient is 0C, and below, but as things start to warm up, the typical resistor selection will cause part of the temp range to exceed the thermistors max spec. If I increase the non sensor resistor, it takes me out of a linear region under normal circumstances, and increased the tolerance bracket. If I increase the thermistors resistance, decrease the SNR, and ultimately the accuracy. So I'm planning to stick with the typical values, and see what happens.

Perhaps at some point I should share the experimental stuff I want to do. I've avoided talking about it, because I've wanted to keep focus on getting the bare min, before going off into some crazy stuff, that probably won't work any how.

as I've offered before, I have gerbers and a sch of my little test board based on the 9924 ... same as gearhead's idea (I think?). Like him, I like to break my projects down into little boards that I etch myself and piece together to converge on a final design.

I'd be interested, I seem to recall you didn't want to post it publicly yet. Should I PM you an e-mail or something? I don't really have much of a need for it, I'm mostly interested as a reference design for when I draw up the board layout I've been working on.

Nice tools. I like those 4 channels tek's. About the lathe, have you seen EMC2? I've been dubbing with OpenServo, and what I've been doing there might be handy for CNCing your lathe if you wanted to do such a thing. In the end, it would be a very low cost servo system.

I recently made one of those toaster re-flow ovens. That thing works nice. Now that I have it, I've been tempted to draw up a brain board. One that includes provisions for 2 cyls, and accepts the hall input, ect. Theory being that if you made this board without the 2 cyl channels off the end, it would be a replacement for the TA card.

[EssEss]

abe - thats some cool stuff. you have a link to that where we can find out more ?

jared - I'll just make a new thread and post all my 992x info in there for everyone. also, the scope an ps are sitting on my cnc'd mill I use mach to drive it. The lathe has been on the todo list for a loooong time.

[AbeFM]

In the interest of the thread topic... I'd really like to see something as 510 described. Very simple, very throw away boards (ideally, not with expensive components) FOR DEVELOPMENT.

That means, first off, little niceties can go - P&H injector drivers, while I'm not against them, are a bit pricey and not needed for testing. I'd probably either use resistor packs or jean's board. After having a board with normal drivers, there would be an alternate board (the beauty of modularity) with P&H drivers.

In reality, I'd lay out a board with both and you populate what you need.

As to any ill-defined pins: You put two jumpers near each other, basically three vias. You put a trace between two holes. Cut trace number one and solder in a wire jumper if you decide you need the other option - but it's more robust and more simple than a complex series of boards, and better for development - it's reversible, etc.

I love the idea of stand offs.

So, I say we collect a 100% agreed upon pin-out, and post it here. We should include possible places (so the pin-out isn't 1:1 but more like 2:3.
We should come up with a sensible set of boards and their division. I really like the idea of a buffer chip, and being able to run it either way is genius. Again, all jumper configurable.

If I had a board stack and a parts list, I'd put one together and get my car on it yesterday. Hand wiring, I think there's no drive for improvement. So let's keep whining about which features are being left off to an ABSOLUTE MINIMUM, and figure out how to chop it up. I'm sure we can print stacks of 3-4 boards for <$100/set, and go find out what dumb mistakes we made.

I like the idea, so we can do things like rapid development on our own P&H circuit (which I liked), only swapping out the one part at a time. If someone wants to do the layout/schematic, great. If I need to, perhaps I can - though I'd appreciate it if more experienced people would lend some advice. Let's frame the problem, come up with design goals/philosophy by the end of the week, and start drawing before monday.

Gearhead, I'm hoping this will provide the final input to solidify your design, which I still think is awesome. I DO like the idea of eventually making a card with the processor, maybe some power and coms.
-Abe.

P.S. MiataTurbo.net has all the real info. Lots of pictures here http://abefm.smugmug.com/MegaSquirt-Stu ... apterboard
General Info: http://www.miataturbo.net/forum/t36300/
Baseline MSQ: http://www.miataturbo.net/forum/t38677/
There's a thread here, too... http://www.diyefi.org/forum/viewtopic.php?f=6&t=715 but I don't know if there's any real info about it.

[jharvey]

Any objection about splitting up the layout I've drawn up, and make it's sub sections? I made this kind of modular, if one were to split it up with a break shear, it could function as you noted above. The sub sections could be split up via software, as opposed to a break shear. Just delete what you don't need, and perhaps add a couple via's so you have some pads to solder to.

The ignition and injection drive circuits could be made into square boards. The RPM input could nearly be a square board, I think the only one that it's fairly straight, is the regulator. That's mostly because it's the power feed, and it weaves in and around.

I also tried to secretly plan for an expanded version of this board. You can stretch the board out by copying the injector and ignition sections making it an 8 cyl, instead of 6 cyl.

It's a 2 layered PCB, with the components all on one side, so it should be fairly easy for the role your own PCB folks. Could be done as a single layer, with a bunch of jumpers on the other side if one wanted to go that route. The key annoyance in making it, is that it has several vias for the thru hole components. For those that have CNC a mill, those via's might not be much of a problem.

I'm certainly willing to help split it up if some one wants to role their own boards.

[AbeFM]

See what everyone else says but it's fine by me. Keeping size to a minimum isn't as important in the test board. As I recall, the injector circuits (for instance) were never entirely figured out - this would be a great opportunity to try them...

I would say if you lay them out with an eye on getting them printed, at this stage perhaps a small run of ten boards (even if they come in 1 piece and you cut them yourself) would make it more accessible to all.

Do you want to give breaking it up a whirl? My long term assumption is eventualy there will be a serial/processor/power card - something which is entirely non car specific and general purpose enough (perhaps some dangling CANbus or whatever) that it could be used in a toaster, a car, or anything... Basically to take the place of the TA card. For me, personally, I'd at least want a USB interface - but no reason to do that now unless there's one we want to test.

What do you think? I like the idea of a Massive GPIO Board. Maybe, down the line, something with timers?

[AbeFM]

Heh. Hello?

[510rob]

If there is to be a dictator, it's the guy designing the board. After all, he doesn't have to, and someone else could up and do a different one as well. I'd prefer (as with my firmware) that our effort was united in the short medium term until we have a functional basic working foundation. This is the best thing for the whole community in the long and short term. I'd prefer that both firmware and hardware were thorough and reliable and cleanly implemented and as simple as possible while doing things the right way. Hence if you ask me, no current feedback and no switched adc, at least, not hard wired in, perhaps via external add on board?

The min has to be

• 4 inj
• 4 ign
• 1 fuel pump
• 1 regulator

I would prefer to make it

• 6 inj
• 6 ign
• 1 fuel pump
• 1 reg
• 2 spare

So that a turbo 6 cylinder guy can do boost control and idle control without mods.

I guess we need a basic layout to see how small we can get it without issues and without making compromises to the basics.

Certainly if we go much over 10 to220 parts we will need to use two sides for FETs or vertical mounts on the board or both.

If there are spare FETs included they should be attached to the port P pins for PWM use.

Fred.

Just to get an idea of the scale of things here:

• How many people are planning on doing firmware coding?
• How many people plan to implement a raw prototype system on an engine, and
  of how many cylinders?
• How many people actually think they might want a prototype board set, where
  the express purpose of these boards is as a short-term solution to allow more
  efficienct and effective coding, not necessarily a perfected board that is 'good' in
  the sense of weatherproof, automotive temp grade components, etc... ?
• Where are we at with respect to the general consensus of the ideal 'initial config
  for development'?