PCB layout - JHarvey

[AbeFM]

As in here, I'm not seeing it the way you described. I called it "U1A" and "U1B" and everything carried through fine - I hooked up both power pins, and everything just worked when I brought it into layout?

[jharvey]

My problems with the op-amp are related to the XOR issue. I noticed it first when the opamp power was high lighted and the constant power reg net light up. After playing a bit, it seperated like expected, but the XOR chip still lights up when the net select is on the constant reg net.

I'll just make a symbol for the XOR and it'll be fine.

EDIT

Also note, the markers on yours. What is it complaining about?

[AbeFM]

Oh yeah - I didn't think about that. Er, they are 'undriven power pin'....

Now you've got me thinking: I bet my drawing isn't working as well as I thought it was. I just know it came across ok and the traces seemd fine, but it's not 'correct' perhaps.

[jharvey]

So I made a symbol for the XOR and the nets work just fine now. Resolve they way they should ect. Also I corrected the wrong connection to the opamp, and I'm making progress again.

Looks like after the three general FET circuits, I'm really forced to either copy the ignition / injection drivers, or move the RPM circuit on the board. That's going to be a tough one, I think the caps are to tall, and I'd rather not put those caps on the other side of the PCB if I can help it.

Perhaps the caps can go on the bottom side bent over, Hmmm, how to fit it.

[davebmw]

Sorry I must be a little retarded or something, why are you considering the use of Op amps to buffer a digital signal?
Can't we just use 4000 series logic with opto-couplers to provide isolation and MCU protection?
is this signal going to be that dirty that it needs filtering if so a window comparator should be the way to go.
Or am I missing something vital here??

[jharvey]

This circuit is what is used by an OEM. It filters and adds some hysteresis. The hysteresis could easily be done with some form of a Schmitt trigger, but then you'd also have to filter out some noise junk. The pro's of this circuit are that you can adjust the filter and hysteresis, where other circuits are harder to control. I'm sure it could be done several different ways, this one has some field testing, so it got included.

[davebmw]

This circuit is what is used by an OEM. It filters and adds some hysteresis. The hysteresis could easily be done with some form of a Schmitt trigger, but then you'd also have to filter out some noise junk. The pro's of this circuit are that you can adjust the filter and hysteresis, where other circuits are harder to control. I'm sure it could be done several different ways, this one has some field testing, so it got included.

Good enough for OEM, good enough for us

[AbeFM]

So I made a symbol for the XOR and the nets work just fine now. Resolve they way they should ect. Also I corrected the wrong connection to the opamp, and I'm making progress again.

Looks like after the three general FET circuits, I'm really forced to either copy the ignition / injection drivers, or move the RPM circuit on the board. That's going to be a tough one, I think the caps are to tall, and I'd rather not put those caps on the other side of the PCB if I can help it.

Perhaps the caps can go on the bottom side bent over, Hmmm, how to fit it.

Hmmm....
1) What did you have to generate a part for? I'm still trying to find a nice way to do this, I want a 50 pin header and it's driving me batty - but more to the point I wonder why the XOR's you already used didn't work.
2) I know people will yell, but could you get a surface mount cap, to save on vertical space? How much capcitor do they need?

[AbeFM]

Quick question: It seems like each of the power nets (+12, +5, GND) in my board have ONE error that says power pin undriven, and I guess it selects that at random. Is there something to DO about that?

No other errors, though I still have to check the actual logic and correctness of it, it seems to work ok.

Oh and I guess I should probably figure out the footprint thing - I have both done but don't know how to tie them together yet.

[jharvey]

Quick question: It seems like each of the power nets (+12, +5, GND) in my board have ONE error that says power pin undriven

I get the same. I've been ignoring it, but I believe the way to fix it has something to do with the "power flag" power port. I took it as an error that didn't effect the traces and nets, so I blazed a trail.

1) What did you have to generate a part for? I'm still trying to find a nice way to do this, I want a 50 pin header and it's driving me batty - but more to the point I wonder why the XOR's you already used didn't work.

I feel the same, I feel they didn't work because of a lack of understanding on my part. I also feel like making the symbol that doesn't use power ports is the easy way out. I would like to learn how to use them correctly, but also I want to keep moving forward with the layout.

2) I know people will yell, but could you get a surface mount cap, to save on vertical space? How much capcitor do they need?

I know some wouldn't be a problem, they could probably come as 0805, and solder right across the thru holes. The 33uF might be a different story. I'd have to go look that one up.