Arduino as ISP Shield

When I started playing with AVRs I started like most people. I bought an Arduino starter kit, then added on. And then added some more. Quickly I realized that a lot of projects need far less then an a $30 boards potential. So the Tiny series was a beautiful discovery. They're popular that's for sure. 

I have a USB Tiny ISP from adafruit that I love because i got to assemble it. I mounted a small breadboard to it and it works great. But it likes to slid around. I do have 3 Arduinos mounted to plexiglass plates with half size bread boards. The make great programmers for the tiny AVRs. They take a bit of time to set up. Since I've started using OSHPark making custom boards is obtainable. They also have a large user contributed project section a but of searching found the Pixie85, Pixie2313 and Pixie84 boards. These simply add an ISP header to the chips. Brilliant. I added chip sockets and boom easy to swap out a chip. That solved the messy breakouts with the USBtinyISP. 

My solution to the Arduino setup issue was a custom shield. Searching arduino isp on OSHPark came up with solutions the had sockets for only a certain chip, or were just clumsy to use. I liked Arno's Tiny ISP shield but the chip socket was a deal breaker. So I set about making my own.

Mistakes happen when designing circuit boards. Sparkfun has made a few interesting mistakes on boards. This one had two mistakes, one being a "unintended feature" that I might keep. This is Rev 0.2 because the first version I some how added a 2x3 header with 2mm pin spacing that was caught before I submitted to fab.  The Second issue is easily seen in the completion photo. I miss counted the offset of the headers. The holes for the headers were loose enough to allow a slight angle. So my design is  .07 inches less wide that it should be. It saves 20 cents a board and nothing is stressed but the angle. it sides on perfectly since I soldered the headers in while attached to the Arduino. My test board didn't need the cap, matter of fact it hindered operation and wouldn't allow the Arduino to work. The LED's are designed to be optional. the wires come from under, The holes need to be slightly bigger, a 22(7) wire was too big, I had to remove a strand to get them to fit.

Version 0.3 is slated to have the extra 0.07 inches in width, and the right most led will get a header pin.

Arduino ISP

*** UPDATE ***
I mistakenly added the wrong 2x3 header. It's not a 0.1" spacing. I've corrected it and added a few LED's that you can wire up as per the Arduino ISP sketch. look for v0.2 on the board.
***End UPDATE

Completed, write up here.

For programing tiny 85 and 84 with Arduino, read the high low tech article it'll get you there fast.

Most people I imagine start with playing with AVRs via the Arduino community. Unfortunately moving from your easy to use Arduino to a bare chip isn't easy. It requires a programmer, and those can be as little as a couple of dollars on ebay for a usbtinyisp or avrisp clone. I have a nifty Arduino with breadboard mounted on a piece of Plexiglas that is great for attiny development, especially using attiny85's since the Arduino has power, and I can use it as programmer. Most starter kits come with similar setups, so alot of people have them. It's a pain to setup, and the more wires the more chances to fail miserably. and disconnecting to rapidly test is a little painful.

For the chip side of things I've ordered a few pixie85's and pixie2313 boards. so I'll have the ICSP header broken out. Adafruit has a ICSP breadboard adapter and a 6" 2x3 idc cable... for all of 3 bucks for the set. You'll need some thing similar.

Scouring the internet the solution to my woes seemed to hack a 6 pin IDC cable to use the arduinoISP and an ICSP connector. Sound good but still one of those what pins do I use moment. Adding to the complexity the UNO requires you to disable the auto reset for the serial. This requires a 10uf cap between reset and gnd. Way too much to remember every time. 

The solution is obviously a shield. Unfortunately all the ones I've found already designed are for chip sockets. and we fairly expensive for what i wanted, a cheep, easy to setup programmer board that I could give away.

So the next installment in PCB Design is the ArduinoISP header shield. The LED's are optional, they hook up with wire from "D7-D9" on the back of the board. That gives activity, error, and heartbeat. It didn't add to the price so why not. Also it the cutout on the right so that pin 9 should be exposed.

These are being ordered next week some time. So figure at the end of september I should have them tested.

A simple square inch design that straddles the arduino. I finished the design today. for the uno you need a cap. older boards might need a 120 ohm resistor, though the cap might work too.

It's a bout 5 bucks for the 3 boards. Cheap enough to give away at parties.

OSH park buys

I bought some more boards off of OSH Park. I found them helpful. Only one was my own, and that was based off of another I found but it was very big and big costs money.

LED Simple

My design but I was inspired by Greg's LED board. For a beginner or for teaching that is a better board. It allows visualization. But at 5 bucks a piece someone that has a little more understanding of electronics might like to spend less and get a little more bang.

I have a friend trying to get into micro controllers and these short cut boards can be the difference between learning or tossing a bread board across the room. I also wanted to use these on the edge of a bread board connected directly to either a 74595 or Port D of a tiny 2313/4314. So I added 2 ground pads in the upper corners so i don't have to populate the ground pad. It was a 10 minute board, the routing could be better. These are cheep, so I'm defiantly going to revise this a bit more maybe do the resistors vertical next to the header. the header is going to be slimmed down to 8 pins, the "floating" ground pin makes more sense to me, for versatility. A 4 Led version would be nice too. Also i can see a female header and rubber feet being a good fit as well.

The other boards:

Pixie85 and Pixie2313 Just simply icsp jacks with attached chips. Removes one step and a lot of little wires. That's a win win.

Sturdy Pot Adapter. Simply a briliant way to add a big pot to a bread board. I have huge fingers. I bought 9. that were 1.80 for 3. Simply awesome, every starter kit needs these.