ATtiny84 pin out issues, everyting is correct but nothing works.

Hello guys,
I'm having some really strange issues. I have worked with Attiny85's and have had no issues. So I don't know whats going on here. I have tried 2 different Attiny84 core's and even both pinouts that exist and I can not get my project to work from just the Attiny84 chip.

I can upload the blink sketch and have it blink an LED on Pin D3 then I turn around upload my Sketch to the same chip and then it will start blinking the LED on D3 when I call to have it blink one on D8.

It also seems to just lockup inside my project. I had a Atmega328 in there and it was working just fine, I put a Attiny84 on the bread board and moved over jumper by jumper to the attiny84 and inside my code reassigned all the appropriate pins and when I hook up power it just does nothing.

Anyone have a single clue what I could be doing wrong.

UPDATE!!
Pulling my hair out, If I hook up another Attiny84 in parallel with the one that i have in my circuit just the power and ground on the second chip and nothing else the whole circuit functions and all my input and outputs all work... I don't understand this at all.

I played with it all night and still can't figure it out. I guess I'll build this project one layer at a time till I find what's triggering this behavior. I can't for the life of me figure out how wiring another chip in parallel can cause everything to work correctly.

Did you forget to install the 0.1uf decoupling cap between Vcc and Gnd right next to the chip? That is necessary, and just bout every imaginable failure mode can occur if you omit that cap.

Otherwise, I blame loose wires/poor connections (are you using breadboard? This is a constant issue with that stuff)

DrAzzy:
Did you forget to install the 0.1uf decoupling cap between Vcc and Gnd right next to the chip? That is necessary, and just bout every imaginable failure mode can occur if you omit that cap.

Otherwise, I blame loose wires/poor connections (are you using breadboard? This is a constant issue with that stuff)

I didn't install any caps since the atmega328p was working just find moments before I swapped it out for the attiny84.
But could the whole hooking up the second attiny84 in Parallel be the reason it works because it's acting like said capacitor? Although when I do standalone attiny85 stuff I don't use caps and those projects work fine also... hmmm

NONE of these chips are expected to work without a cap. It's perfectly belivable that a small change in the capacitance of those two lines from another chip being connected to it is enough to make it start to work. It's still not in spec and may "randomly" reset under normal operating conditions.

Atmega328p's often look more like they're working without decoupling caps than attiny's - they may work normally while programming, but will unpredictably reset while running the sketch (or they may start to program and then fail partway through, etc).

The 0.1uf decoupling caps (located as close to the chip as possible) are NOT optional, and your board is EXPECTED TO FAIL without them - it is just luck if it works at all (bad luck, imo - because if it just plain didn't work at all, you wouldn't be arguing with me here, you'd have been told to use a cap, installed one, and it would be working now).

I had to throw out a dozen copies of a board I had made for an ATTiny85, because I'd placed the decoupling cap too far away, and it wouldn't program unless I put another 0.1uf cap across the top dead-bug style.

So you must use 0.1uf decoupling cap (ceramic) between power and ground, right next to the chip. Do this for EVERY digital IC you use unless the manufacturer's datasheet explicitly says not to - the vast majority of such chips need it for reliable operation.

0.1uf ceramic caps are very cheap - 2-3 cents each for through-hole ones in lots of a hundred or so. I'd say they're the most important single component to own.

Could I use something in the 22 micro range to just test and see. I don’t have any that small .1uf

Nope.

0.1uf. 0.22 uf is probably okay, but I wouldn't try to use anything higher than that. 22uf won't work.

0.1uf ceramic cap. It is the single most important electronic component for any electronic hobbyist to own.

Digikey: http://www.digikey.com/product-detail/en/vishay-bc-components/K104K10X7RF5UH5/BC2665CT-ND/2356879 ($8 for like 100, shipped to US, ~3 day shipping)

EBay: http://www.ebay.com/itm/221517912781 $1.09 for 100, shipped worldwide via ox-cart (1~4 weeks to US)

Thanks a lot I'll get some and see if that's what's screwing everything up. See if I can scavage one from something tonight and try it and see if it fixes it

Yeah - they're easy to find in other devices. They may be marked "104" (shorthand for 0.1uf) - should fine some around any ic.

http://www.dipmicro.com/store/C5K10-50
Get yourself a small bagful.

DrAzzy:
Yeah - they're easy to find in other devices. They may be marked "104" (shorthand for 0.1uf) - should fine some around any ic.

You deserve a medal dear sir or madame. I am blown away that it was in fact the decoupling capacitor. I got home dug around and found a .47uf one hooked up across the chips Vin and GND and walla it worked perfectly.
It's amazing that you could figure that out from my crazy scenario. You are in fact right I think hooking up the other chip just gave enough capacitance to get it to run.

I'm blown away that I haven't had any other chips do this till just now. All my attiny85 and atmega328p-pu projects have all ran flawlessly till these attiny84s.

Thank you big time

CrossRoads:
100nF/50V Radial Ceramic Disc Capacitor - dipmicro electronics
Get yourself a small bagful.

This seems super cheap and it ships from Canada? There is no data sheet on them will they work in below 0 temps?

Y5V dielectric though - that’s part of why they’re so cheap. They lose significant amount of capacitance at high or low temperatures.

X7R (or at least X5R) has much better stability over temperature ranges, and is almost as cheap, and that’s what I use. Certainly if you’re planning to use them in unusually low or high temperatures, you should get X7R.

DrAzzy:
Y5V dielectric though - that's part of why they're so cheap. They lose significant amount of capacitance at high or low temperatures.

X7R (or at least X5R) has much better stability over temperature ranges, and is almost as cheap, and that's what I use. Certainly if you're planning to use them in unusually low or high temperatures, you should get X7R.

O I tried the .47uf and the circuit worked and then I tried a cap with 103k on it which I think is a .01uf cap and the circuit worked lol either way if I remove cap it all stops again