144 LED Games Console Project

[mtripoli]

This is really an edit, time expired when I went back...
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@funnydrummer: You don't need resistors on the base of an emitter follower so you can delete those entirely. If you're opposed to using resistors for current limiting (which is the only reason I can see to stack up diodes like you have from the supply, (which is a really bad idea but I'm not going into that) you can use a constant current regulator (CCR) device like the NSI45020T1G from ON Semi (Mouser, $0.34 each). If you use a CCR device you can get rid of all the transistors and resistors entirely and use just the CCR. Put one per drive segment (they can be used high side or low side, see attached schematic). Run the PIC from 5V (voltage regulators are a good thing, why you wouldn't use one I don't know) and there you go.

You're going to need a 0.1uF on each Vdd pin, not just the one you have on the power supply line. While you're at it I'd put at least a 100uF cap on the power supply line as well. It doesn't look like you have a connector for doing ICSP so writing code and debugging will not be any fun at all (unless you like pulling a 40 pin part from a socket for every little change you make to code). If you plan on clipping to the PIC for programming you have no provision for isolating the Vpp line. There is no electrical reason at all for using pull-ups on two switches and pull-downs on the other two, as well as keeping track of that in code is unnecessary. You really should look at the schematic I posted. And why would you post C code on the Pic Basic forum?


@Svrzic: The PDF schematic that is posted is FOR DISCRETE LEDS. Regardless if you buy them packaged or use discrete components the schematic is the same. I think you said you're 17 years old. Good for you for your interest in electronics but it sounds like you need to back up a bit and start with something a little easier.

Attachment 6142

[funnydrummer]

@funnydrummer: You don't need resistors on the base of an emitter follower so you can delete those entirely. If you're opposed to using resistors for current limiting (which is the only reason I can see to stack up diodes like you have from the supply, (which is a really bad idea but I'm not going into that) you can use a constant current regulator (CCR) device like the NSI45020T1G from ON Semi (Mouser, $0.34 each). If you use a CCR device you can get rid of all the transistors and resistors entirely and use just the CCR. Put one per drive segment (they can be used high side or low side, see attached schematic). Run the PIC from 5V (voltage regulators are a good thing, why you wouldn't use one I don't know) and there you go.

You're going to need a 0.1uF on each Vdd pin, not just the one you have on the power supply line. While you're at it I'd put at least a 100uF cap on the power supply line as well. It doesn't look like you have a connector for doing ICSP so writing code and debugging will not be any fun at all (unless you like pulling a 40 pin part from a socket for every little change you make to code). If you plan on clipping to the PIC for programming you have no provision for isolating the Vpp line. There is no electrical reason at all for using pull-ups on two switches and pull-downs on the other two, as well as keeping track of that in code is unnecessary. You really should look at the schematic I posted. And why would you post C code on the Pic Basic forum?

Thanks a lot for the suggestions, I really appreciate it!

Too bad I already ordered the PCB, it's a big one so it would be a bit costly to order a second one.
I might edit and optimize the schematic/board in the future, but for now I'm just hoping the current board will do.
The next thing to do is programming. ;-)

Good point though, this is forum isn't called PIC-C...
I'm not familiar with basic programming, that's why I'm just gonna go with C.
I thought it would be nice to post the source anyway, just for the people who prefer C over basic.

[mtripoli]

@SVRZIC: This is becoming a language problem of epic proportions. I've negotiated a full weeks "company" with a lovely Asian girl in China in less time and with less confusion than what's going on here. Are you saying that you want the led matrix redrawn with the little arrows added to each diode in the array? Man, I hope not... Go to Kingbright (www.kingbrightusa.com) and put in the part number TA20-11E and look at the data sheet. Maybe also try using Google Translate and writing out exactly what the problem is in your native language and then posting the translation here. It may not be perfect but maybe it'll clue us into what you want.

@funnydrummer: I'm sorry to hear you already released the board. At the very least you'll need to tack solder in the decoupling caps across the VDD/VSS pins on the part/socket. Also as I said, you have no provision for doing ICSP. Those pins don't take kindly to having "stuff" hanging off them while programming. You don't need R1 through R8 at all so when you build it put in wire jumpers instead of resistors. Kludge in a dual SPST switch soldered across the pads in place of the resistor and hot glue the mess to keep it solid so you don't tear pads off the board. You can still get these "Test Clips" made by 3M and Pomona. Mouser has one for $45.96 (http://www.mouser.com/ProductDetail/...2ft7rMmGLEo%3d). You can again kludge the wire ICSP wire from your programmer to th eclip and then clip onto the part in the socket to flash the part. OF course, you have to figure out how well your programmer will work with a length of cable between the programmer and the DUT. I know from experience that the Melabs U2 is very forgiving of cable length (read "designed well") and I've managed some wires solder tacked in place to update a part in the field. The PicKit3 gives all kinds of errors one minute and works for days the next if you happen to bump the programmer cable (your mileage may vary). And if you don't put a series diode and resistor on the Vpp line you'll be stuffing something like +13V back onto the supply line. Hmmmm... Not so good.

Your statement "I thought it would be nice to post the source anyway, just for the people who prefer C over basic" gave me quite the good chuckle. Yup, ALL KINDS of people who prefer C hanging around the Pic Basic (not just basic mind you, but Melabs Pic Basic) forum. And the PBP guys love answering C code questions, don't we fella's? Perhaps its something more like the PBP crowd is a bit more helpful than those on other boards and try and actually give people a hand with getting their stuff going. That is until the end when after offering all kinds of help the finally admit to using some kind of C or "other" Basic program and admit they can't get any help on the other boards so they come here.

AS for me, I'm out. This thread has me weary (again) and I just had to put my dog down after 16 years so Right Now I couldn't care less if your project works or not. Do yourself some real help; look around the board at how people have designed their circuits and watch for commonalities. Get one of any number of "Programming PICS" books and do some reading. Read the damn datasheet for a programmable part and make sure you have some way to program it and if it has more than one VDD pin take it as gospel they all get a cap tied to them right at the pin and solidly to ground, not across the PCB as you've demonstrated. 20MHz huh? Good luck with that...

Ciao.