I've been playing with attiny85's recently and while they're great fun, programming them in a breadboard with jumper wires is rather annoying.
I've found a couple boards along the same line, but modeled after the RBBB, and lacking a power supply section.
To remedy this I've downloaded Eagle and designed myself a attiny version of the BBB, my current favorite Arduino clone. It has pins that stick down into the + and - rails of the breadboard, and then nicely arranges the IO pins in order from 0 through 5. Eagle doesn't have two pin connectors, so pretend the empty pin on the 3pin connector doesn't exist
This is only the second thing I've designed with Eagle and I have no experience doing this sort of thing, so I'm asking for opinions before I spend any money on it!
I haven't figured out how to make nice looking pictures out of the board design, so reading the values on things is kind of rough.
The schematic copy/pastes better, thankfully.
Any/all input is welcomed!
EDIT:
A note on the voltage regulator: I picked a random 5v TO-92 regulator, I probably won't actually use that specific flavor.
A note on the IC: Eagle doesn't have the attiny85 in it, but the pins look to be the same as on the 13 that Eagle does have. If they aren't, that changes everything!
A last note: The one red trace is going to be a jumper wire, I'm not making this double sided just for one connection! (Unless it's no more expensive to have made...)
Flip your regulator over, and the board will route better. You can also used the TO220V package (3 pins on 0.1 inch centers, inline) and you'd be able to use either TO200 or TO92 packages (the "triangle" TO92 layout is less common these days; many parts come with the leads pre-formed in the inline shape.)
Avoid the accute angles between traces (try to meet only at 90 degree angles.)
If you're having boards MADE, double-sided is only slightly more expensive than single-sided (and you'll probably get a better deal on DS from a place like dorkbotPBX than you'll find from any place that has a lower price on SS boards.) I'd only worry about doing a SS board if I was making it myself.
(Go ahead and change the "value" of your regulator and IC to reflect their real values. EAGLE will say "do you really want to do that", and you can say yes...)
Thanks for the input!
With it, I have designed revision 1.1, or 0.2, or something like that.
It's still probably not the final regulator, if I recall correctly these things have a 2v voltage drop, which is a bit much for my tastes.
I also had a brainstorm and hacked almost half an inch off the length, and moved the caps between the regulator and the attiny.
I like it much better now. There's one trace that goes waaaay down around the bottom that I don't like much though.
Thoughts?
(Sidenote, thank you for the link to the nice cheap dual side purple PCB place, I'm almost certainly going to be using that!)
(edit due to post while I was writing this: That (12v regulator) is what I get for not reading what exactly I was clicking on!)
Why not put the two breadboard power pins in line with the IO pins? That way the whole thing plugs straight onto a breadboard. As it is you'll have to run flying wires from one or the other.
The separate power pins should line up with the breadboard power rails on standard modern breadboards, something I really like about the BBB. It's also a holdover from the first single sided version, getting all 7-8 pins into one line single sided was very messy indeed.
How thick should the power (and other) traces be? How can I set the width of a specific trace in Eagle, anyway?
I think I know how to do the ground plane polygon thing, I'll do that. Should I put ground on both sides or make one a vcc plane?
The offset matches (more or less) the BBB I have in front of me, I think I'm going to change it to a single 7 or 8 pin connector if I can make it route nicely though.
10pf is my guess from memory at the smaller of the two filter/smoothing caps that the regulator and the attiny like to have. Am I totally out to lunch there?
10pf is my guess from memory at the smaller of the two filter/smoothing caps that the regulator and the attiny like to have. Am I totally out to lunch there?
I have no clue about the regulator but, in my experience, you would be well served to include a 0.1 microfarad capacitor across the processor's power supply. With no capacitor, the analog-to-digital converter on ATtiny85 processors just does not work well. I have no idea if a 10 picofarad capacitor is a reasonable substitute.
The separate power pins should line up with the breadboard power rails on standard modern breadboards, something I really like about the BBB.
Shouldn't the three pins be offset 0.3" to the left in order to line up with the breadboard power rails? Maybe I'm missing something....
Don
The offset matches (more or less) the BBB I have in front of me, I think I'm going to change it to a single 7 or 8 pin connector if I can make it route nicely though.
In order to match your pc layout I am assuming that your breadboard will be orientated vertically with the blue '-' rail at the left. The red '+' rail will be directly to the right of that and another 0.3" to the right is where the main field of horizontally connected rows begins.
As I see it the five pins in the upper left of your board are going to plug into the five of these horizontal rows on the breadboard. Any pins that are either 0.1" or 0.2" to the left of these five pins will not have any breadboard holes below them to fit into. In your design one of the power pins (at the lower right) will fit into the breadboard and the other two will not. None of them match the red and blue power rails. Tell me what I have misinterpreted.
You probably should also have the ICSP pins and the IC further to the left.
Lining those pins up right is proving to be a headache, plus I thought back and remembered times when they annoyed my quite a bit on the BBB. A mixed blessing, those.
As such, I've sacked them for the moment, for bonus points I can make the board smaller without them.
Any thoughts on trace width for signals and for the VCC/GND lines? Or better yet, a link to somewhere with guides to width for a given amperage?
You really should move your capacitors around a bit. The upper 100 nF capacitor should be on the left side of the regulator next to the pin it is bypassing. The center capacitor should be connected directly to the output of the regulator, not at the far end of the Vcc line. The lower 100 nF capacitor should be as close to pin 8 as you can get it. You should also identify pin 1 on the ICSP connector.
Ok here's what I came to post (now that I've seen the latest advice I'll change things), now with a ground plane that I'm rather pleased with on the top side. Should I put a matching one on the bottom side?
All the VCC and GND traces are .04, though I really have no clue how large they ought to be.
Total size is roughly 1" x 1.1", nice and small/cheap.
Now that I'm happy with this version I'll sack it and shuffle the caps around, heh. I appreciate the input, it's nice to learn.
Yeah, I'd certainly like to at least.
Some sort of power supply and arranging the pins are the main order of the day, I can always add the reset pin to the breadboard connector and then make a ICSP-Breadboard dongle if it makes things way easier (which I think it probably would).
It'd be nice to have the full thing there though, might be something I could actually sell a couple of (ideally enough to pay for the eagle license required to sell things...).
