We need to lay out a basic board

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jharvey
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Re: We need to lay out a basic board

Post by jharvey »

I see inclusion of what appears to be a snubber diode, and perhaps a power resistor. Do you have a schematic that would help indicated how the hip bone is connected to the leg bone?

I agree that for a proto, you can use a protected MOSFET with out any additional protection like Fred did in the Volvo. No snubber, no buffer, just that one little guy and a couple connections. Additional protections are typically just for longevity and robustness.
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Re: We need to lay out a basic board

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Requirements:
1) Power supply
2) 6 analog inputs (CLT, MAT, TPS, MAP, TP, Batt)
I'd love to see lots of inputs. This allows maximum flexibility and playing with now. How much overhead is involved?

3) 6 injector outputs
4) 6 low current ign outputs *no high level coil drivers on board, these should be separate*
Absolutely agreed. Not that many cars use it and it's not hard to build on an expansion card.

5) Separate ground plane for digital, analog and high current
6) Separate battery sense 12V line which is not used to power any of the ECU components
Is that really that much of an issue?

7) Grounding to be done by low impedance cable (large size) to the block for each ground plane. (These can be jumpered together at the board at your own peril.)
People worry too much. And I have noise issues. :-)

8) No LowZ injector drivers on the board. If you want to put in a header to drive Jean's boards, I am fine with this as there may be people trying to run FreeEMS to develop it with LowZ injectors
Agreed. I would love to have them, but can use another board for now, develop it later.

9) Extra high and low current drivers which can be used as either I or O, have 5V digital nearby for pull up. 12V pullup does not need to be as easy to get, but could be used in the case of certain I or O.
10) no current sensing needed on board as part of layout. KISS
Agreed, again. As slick as I think it is, it's a bad time? Perhaps leave some vias so someone could piggyback a circuit if they wanted?


What are people thinking about the injector driver chips? There are some good ones.

Having stuff you don't need to populate on the board is fine, especially if it can be bandsawed off. :-)

I'm a fan of taking advantage of the awesome chips which are available, use a protected chip for outputs. For that matter, some of these parts (like the VDN ISOWaTT200 package). Surface mount parts are NOT that challenging, the reasonable ones, and it'd be cheaper and faster and smaller and perform better... If they are too hard to find, then they are, then again, perhaps it's better for a final design.

I guess all in all we're still waiting on a pin-out. My personal feeling is to MAKE A BEST GUESS, MR. FRED, and move on. If it changed later, it changed. The thing keeping everyone from getting involved is the pinout bottleneck.
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Re: We need to lay out a basic board

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3) 6 injector outputs
4) 6 low current ign outputs *no high level coil drivers on board, these should be separate*
Absolutely agreed. Not that many cars use it and it's not hard to build on an expansion card.
I'm coming around to this way of thinking now. I was thinking "people will want it, give it to them" but now I'm thinking "educate those bastards and make them do it right".
5) Separate ground plane for digital, analog and high current
6) Separate battery sense 12V line which is not used to power any of the ECU components
Is that really that much of an issue?
YES!!! Fully agree with this. Even my FreeEMS setup on the Volvo had this. Do as you preach, I thought and soldiered on.
7) Grounding to be done by low impedance cable (large size) to the block for each ground plane. (These can be jumpered together at the board at your own peril.)
People worry too much. And I have noise issues. :-)
People don't worry enough. This needs to be the case, even when things are done right. I found this out on the Volvo too. Another example of practice as you preach. Large ground wires ftw.
8) No LowZ injector drivers on the board. If you want to put in a header to drive Jean's boards, I am fine with this as there may be people trying to run FreeEMS to develop it with LowZ injectors
Agreed. I would love to have them, but can use another board for now, develop it later.
Ditto, +1 here too.
9) Extra high and low current drivers which can be used as either I or O, have 5V digital nearby for pull up. 12V pullup does not need to be as easy to get, but could be used in the case of certain I or O.
10) no current sensing needed on board as part of layout. KISS
Agreed, again. As slick as I think it is, it's a bad time? Perhaps leave some vias so someone could piggyback a circuit if they wanted?
Agree with gearhead's original statements in this regard. Also ground pull down handy too. Resistor always solders in one hole and other end moves between adjacent three. Resistor can mount vertically to save space.
I'm a fan of taking advantage of the awesome chips which are available, use a protected chip for outputs.
I don't want to see any unprotected IO on the thing. Protected FETs for everything of any significance. They are easy to find and there are heaps of alternative part numbers to choose from. There wont be a "you must use this" situation for freeems fets, hopefully.
I guess all in all we're still waiting on a pin-out. My personal feeling is to MAKE A BEST GUESS, MR. FRED, and move on. If it changed later, it changed. The thing keeping everyone from getting involved is the pinout bottleneck.
Yep, agreed. It certainly IS going to change though, so getting the ground work in and figuring out what the pin state anomoly is is pretty important in my eyes. Before I noticed them doing weird things at start up I wasn't concerned. But since then I want to understand the hardware, if not, we are driving blind and will surely crash. Anyone with a card can dig up that thread and mess around till they suss it out. That includes you, Abe, put your time where your mouth is :-) I'll do it sooner or later if no one else does, it's just a matter of priorities. Getting the existing code out and the website and forum up to par are higher right now. Once those are done, this, scheduling and RT code and the serial interface design and code are all of high importance. Hopefully we can split the workload somewhat this time.

Fred.
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Re: We need to lay out a basic board

Post by AbeFM »

Fred wrote: Yep, agreed. It certainly IS going to change though, so getting the ground work in and figuring out what the pin state anomoly is is pretty important in my eyes. Before I noticed them doing weird things at start up I wasn't concerned. But since then I want to understand the hardware, if not, we are driving blind and will surely crash.
Interesting, I didn't know that - or didn't retain it. Do you have a link to where you see this and how to test for it? Certainly that would be a bad one to screw up too bad, too early. Then again, the board could plug into a socket with dual rows of vias connected by jumpers. WORST CASE, you cut three leads, jumper them to each other. Make sense?

Image

Right by the jumper block I shamelessly stole from Jean, you can see a jumper I put in, then I just (in layout, and in the schematic) put a trace in between it. It gives you a highly reliable, solid connection, but if you had a row of ten of these, it would be trivial to go from:

01-02-03-04-05-06-07-08-09-10
01-02-03-04-05-06-07-08-09-10

to
01-02-03-04-05-06-07-08-09-10
01-04-03-02-05-06-10-08-09-07

by razorblading 4 traces and adding some wires. I would recommend we do that ANYWHERE we're not sure what we're doing, it's easy, and even allows after-the-fact series diodes or resistors or other signal interception manipulation, and takes up hardly no board space at all.

Fred wrote: Anyone with a card can dig up that thread and mess around till they suss it out. That includes you, Abe, put your time where your mouth is :-)
Jesus, call my bluff why don't you? :-) I DO need to figure out how to make my computer talk to my PC. Then I guess there's no reason I couldn't. I once traded room and board for a week of a real pro's time to come train me on all this, but he just sat around buying me bottles of wine instead.
Fred wrote: I'll do it sooner or later if no one else does, it's just a matter of priorities. Getting the existing code out and the website and forum up to par are higher right now.
Maybe. :-)
Fred wrote: Once those are done, this, scheduling and RT code and the serial interface design and code are all of high importance. Hopefully we can split the workload somewhat this time.
Hence the suggestion - getting the pin-out worked out will really, REALLY help this to move forward. The scheduling code can be done while other people work on hardware - since you have only a passing interest/expertise in the actual layout, it's a great time to let the people already into it have the tools they need to get started building the hardware - then when the software is there you can just load it on.

Perhaps I'm oversimplifying, but it's not a question of what's most important, rather, which things in which order will yield the best output in the shortest time (and in this case, "best" means flexible, cheap, and easy to learn from).
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Re: We need to lay out a basic board

Post by Fred »

Interesting, I didn't know that - or didn't retain it. Do you have a link to where you see this and how to test for it? Certainly that would be a bad one to screw up too bad, too early.
Here is the link, there may be more info distributed around, or it could be all in that thread. Post/PM/IM me with any questions if you are serious about getting stuck into this.

http://www.diyefi.org/forum/viewtopic.php?f=9&t=510

The comments thread could be worth reading too.
Jesus, call my bluff why don't you? :-) I DO need to figure out how to make my computer talk to my PC. Then I guess there's no reason I couldn't.
Good man, let's get the show back on the road, lead the way, Abe! :-)
I once traded room and board for a week of a real pro's time to come train me on all this, but he just sat around buying me bottles of wine instead.
ROFL, LOL, LMAO, etc, I cracked up loudly leaving the olds wondering what the bloody hell was going on. I got it working... then stole it... sorry! At least I organised you a replacement! :-p Seriously though, I'm online most days now, so hit me up if you need any help. I'm happy to baby you through it, even though I know you don't really need it. As for the wine... the wine buying money supply has run out! :-( Not good. If anyone wants to supply me with wine/gas/food/server rental/etc here is the link http://pledgie.com/campaigns/2414 - I'll be shamelessly pushing this once I publish the code and photos and videos and story behind the USA trip :-)
Perhaps I'm oversimplifying, but it's not a question of what's most important, rather, which things in which order will yield the best output in the shortest time (and in this case, "best" means flexible, cheap, and easy to learn from).
I'm sorry that I've taken so long to get anything done recently, but I've moved countries, several times, in the last 9 months. For a lot of that time my only PC was my EEE that I carried in my bag and car. I might have got more done, except when I started looking to do that, I discovered that the code I had was not the most up to date stuff around, and that I had posted my other PC back to NZ. I've resolved all that now, I just need to sit down and tidy up the code base ready for release 0.1.0.

Fred.
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