What's with mint boxes and electronics? Beats me, but they are somehow made for each other. I had built ladyada's USBtinyISP v1.0 circuit on a breadboard which I used every other day. It worked sporadically(and never at hour of need), used up half of my breadboard and looked ugly. So I decided to try my hand at home PCB fabrication and build it in, of course, a tiny tic-tac box. Since I was a beginner, the circuit is easy and single-sided and uses crystal instead of ceramic oscillator.

Frankly, I didn't even expect it to work so didn't take any photographs. I recently decided to make it again with a few improvements(notice the old orange one has the top backwards) and document it for Instructables. You have to make one of these if you:

want to use bare-bones super-cheap arduinos in your projects
want to burn bootloader to a blank AVR for your Arduino
love working with AVRs
are thinking of buying a programmer

Note: You need to break out of the chicken-n-egg problem and get the program onto the ATtiny2313 used in this project. Check out Step 4 for detailed information and possible solutions.

Edit: Modified board so resonator can also be used for timing! If using crystal, middle pin for resonator can be ignored. If using resonator, no need to solder capacitors C1 and C2.

Step 1: Chicken-egg Downloads

The chicken-n-egg situation while working with microcontrollers is that you need to get your program in a microcontroller to program another microcontroller. I know that's whacky but it's only one-time. There are some ways which I'm listing below. You only need one:

a computer with parallel(or serial) port. The best instructable for a very simple parallel port programmer.
an ATtiny2313 IC pre-programmed with USBtinyISP code (you can buy it from adafruit)
a friend who has an AVR programmer(you only need to beg/borrow/steal it for a few minutes)
an Arduino used as ArduinoISP. You can check this tutorial for ATtiny2313.

I will be using the earlier version of USBtinyISP I made. I had used a parallel programmer to program it's ATtiny2313. You only need a few minutes to upload the USBtinyISP code onto your ATtiny2313, so you can get someone's help who has a PC with parallel port/serial port/AVR programmer/Arduino.

If you're going to someone's place to get ATtiny2313 programmed, remember to download and keep these files in a pendrive:

Get the USBtinyISP firmware from ladyada's USBtinyISP download page. Download the v1.0 firmware(look for the link at bottom of page: "Zip with all v1.0 firmware files").
While you are there, you will also need to download USBtinyISP driver according to your computer.
Download WinAVR. This installs avrdude used to program AVRs.

To use, install all that you've downloaded and extract the firmware zip file to a convenient location.

Step 2: Stuff You Need

Components required:

ATtiny2313 x1
20-pin DIP IC holder x1
USB type-B female jack x1
USB type-B cable x1
Crystal 12 MHz x1
Zener Diode 3v6 x2 (3v3 will work too)
27-68 ohm resistor x2 (I used 33 ohm)
1.5K ohm resistor x5
10K ohm resistor x1
0.1uF ceramic capacitor x1 (cap. code: 104)
12-22pF ceramic capacitor x2 (I used 15 ohm; Cap. code is same as value)
100uF 25V electrolytic capacitor x1
Green LED 3mm x1
Red LED 3mm x1
Male header
Ribbon cable
6 pin ICSP header x2
Female header (optional)

Female headers are not required if you manage to get your paws on ICSP headers. If you can find a pre-made IDC cable, no need for headers or ribbon cable.

Tools required:

Cutter/blade
Plier
Soldering iron + solder

PCB fabrication stuff required:

Single sided copper clad board
Etchant
Drill
Sandpaper
Double sided copper clad board(optional)

Double sided copper board is only needed if you don't have a 6 pin ICSP connector and decide to follow my instructions for a work-around.
Rest of the stuff needed depends on your PCB fabrication method. I use toner-transfer so I need clothes-iron, glossy paper, laser printer etc.

And last but not least, TIC-TAC!

Step 3: Etch That PCB

Download the Eagle files attached at Intro step and etch the circuit into your single-sided copper clad board. This is not an instructable on how to etch PCBs so I'll breeze through it. If you need to learn how to etch PCBs, there are tons of cool instructables out there. I'll be using the famous toner-transfer method.

Recipe for PCB fabrication:

Select only the 16 Bottom, 17 Pads, 18 Vias, 20 Dimension and 45 Holes for viewing. Hit Ratnest.
Click on print. Check Black and Solid and uncheck Mirror options. Set scale to 1.
Print the circuit on a glossy paper(preferably photo-paper) using a laser printer.
Cut a piece of copper board slightly bigger than the printout by scoring with a cutter and snapping.
Use scotch-brite to vigorously scrub the copper board with water.
Wipe with a clean cloth and do not touch the surface.
Iron the circuit printed onto glossy paper.
Dunk the hot PCB in water. Let the paper soften for 5 minutes. Peel away paper and rub away the sticking paper with a toothbrush.
Dunk the circuit into your favorite etchant. I like hydrocholic acid+hydrogen peroxide. While you're waiting for circuit to be etched, pop a few tic-tacs.
After all the unwanted copper is etched away, wash PCB and dip it in acetone(aka nail-polish remover) for a while. Pop some more of those tasty mints. Use scotch-brite to scrub away all the toner ink.
Ta-da! Shiny PCB is served along with fresh minty breath.

Step 4: Drilling, Sanding and Silkscreening

Start drilling holes in the PCB. Use a bigger drill bit for IC pins, LEDs, ICSP header, male header jumper, crystal and an insanely big drill bit for the 2 USB jack pins used for latching it to board.

Now cut off the excess board material from the sides and sand the edges. I also made little grooves for the USB jack's claw-like thingies to sink into. Keep popping tic-tacs throughout this step. It will help you get through the tedious drilling/sanding while increasing concentration and skill(not scientifically proven).

Silkscreen is the outline of components and neat descriptive labels on top of the PCB. Since this is a single sided board, I pasted a printout on the top side of the board. It got blotched and soggy after I cleaned the bottom side with rubbing alcohol but that was just my stupidity. You can also iron the silkscreen the same way as toner-transfer method.

Just select 20 Dimension, 21 tPlace and 51 tDocu layers and print. Cut and paste it but use glue sparsely else it will plug your laboriously drilled holes. If you are using toner transfer to apply silkscreen, leave out 51 tDocu layer and check Mirror option while printing.

Step 5: Program ATtiny2313

Put your ATtiny2313 on a breadboard. The most important pins for programming are: VCC(pin 20), GND(pin 10), SCK(pin 19), MISO(pin 18), MOSI(pin 17), RST(pin 1). The programmer will have atleast 4 wires: MISO, MOSI, SCK and GND. It might have VCC and RST as well. Connect the wires from programmer to respective ATtiny2313 pins. Put a 10K ohm resistor between RST and VCC pins. If VCC from programmer provides 5V, attach it to VCC pin. If not, you will have to provide regulated 5V to your ATtiny2313. If RST is not provided, put a button between RST pin to GND pin. Press this button whenever you upload code to your IC.

Now let's burn the firmware onto ATtiny2313:

Open command prompt and navigate to the location where you extracted USBtinyISP firmware and go to spi folder in it.
Type:
avrdude -p attiny2313 -c usbtiny
Replace usbtiny with your programmer's name. List of programmers can be generated using: avrdude -c ?
You should get output-1(lablled in image) which means everything is working fine. If you are getting error like Output-3 in 2nd image, check wire connections again.
Set the fuse:
avrdude -p attiny2313 -c usbtiny -b 19200 -U hfuse:w:0xdf:m -U lfuse:w:0xef:m
You should see something like Output-2.
Run the command in step-1 once more. You should get an error as in Output-3. This is because you have set the fuse to run off external 12 MHz crystal. Connect crystal across XTAL pins(pins 4 & 5) and connect both pins to ground via 22pF ceramic capacitors. Try again. The error should go away like in Output-4.
Time to burn the firmware:
avrdude -p attiny2313 -c usbtiny -B 1 -U flash:w:main.hex -b 19200
This should also end successfully. If not, did you have a button connected to RST and did you press it?

Congrats! Your ATtiny2313 is programmed with USBtinyISP firmware code. You can return the programmer you borrowed with heartfelt gratitude and a pack of tic-tac. :)

Step 6: Soldering

Try to keep the solder joint heights low, especially near the USB jack. The USB jack is the thickest part of this project and will make your tic-tac box swollen if the "claws" are not pressed flat or if soldering in that area is of considerable height.

Start soldering the IC holder pins first. Then solder everything else except ICSP pins, electrolytic capacitor, male jumper header and USB jack.

Step 7: Soldering Electrolytic Capacitor

The electrolytic capacitor, if soldered the traditional way, stands pretty tall and will not fit in the tic-tac box. So time to lay it down horizontally.

Solder it in place keeping the polarity in mind, but keep a few mm of leads separating the capacitor from board. Now bend it into a horizontal position. Don't worry if you kept the leads a bit too long and it ends up resting on a pillow of the adjoining resistor, instead of being flush against the board. You just need to make sure that it is low enough to fit in the box.

Step 8: Soldering Male Headers

Now let's solder those male headers. Break away 2-pin male headers and solder them in their place next to the capacitor. Now take your pliers and bend the pins by about 90 degrees.

This easily accessible jumper option is available so that you can power the AVR IC you are programming with USB power supply. Connecting a jumper means target IC will be delivered USB 5V. Removing it will cut it off. Never have a jumper on this if you are powering your AVR with some other source. Clashing power supplies are not good for your AVR and programmer.

Also, if you have a 6 pin ICSP header or IDC cable(cable with ICSP headers pre-connected with ribbon cable), then solder 3x2 male headers in the holes labelled ISP. I couldn't find any of them in local stores, so I made a small hack to replace the cable. If you follow in my footsteps, do leave the ISP holes as is for now.

Solder the USB jack as well and bend those claws flat against the bottom of board.

Step 9: Fitting USB Jack in Top Lid

Hopefully you've managed to empty a tic-tac box by now. Take a blade and cut through the tic-tac labels so the top cap can come off. The top cap's lid will open to reveal the USB jack. For a good connection between the cable and jack, the jack needs to be flush against the top of the tic-tac box lid opening. If you try to fit the USB jack into the cap, it will not reach the opening because of the PCB being stopped by the cap's sides. Mark and cut off a few mm of the cap side as shown, so the board can slide in and the USB jack can sit flush with the opening.

Step 10: Making Makeshift IDC Cable

This is where we may go down slightly different paths. If you have ICSP connector with ribbon cable, then follow the instructions at bottom of this page where ladyada shows how to make the IDC cable from ICSP connector and ribbon cable. Make a hole at the bottom of tic-tac box big enough for your connector and cable to pass through and attach it to the male header pins you soldered earlier, keeping in mind that the dot on silkscreen and key/bump on connector are on the same side.

If you are following my method, then cut off a 6 wire ribbon cable choosing the edge with stripe. Then I stripped and twisted the wire ends and arranged the wires in 3x2 kind of formation. Every alternate wire was on kept on the same side. This then went into the ISP 3x2 holes in the PCB with the pink striped wire going into the pin with the dot(MISO) and soldered. Keep it like this if you are only going to use it on breadboard. But if you want to use ICSP headers on boards like Arduino, then read on. Also, now is a good time to test whether this is working or not.

If it's working fine, cut a slit at the bottom of your recently-emptied tic-tac box and thread the unsoldered end of the ribbon cable through it. Take the mini tic-tac box and cut a slit in it's top cap and a pretty big one at the bottom. Thread the ribbon cable through the top and out of the bottom.

Step 11: Making ICSP Connector

Etch the simple ICSP connector circuit whose Eagle schematics I have provided at Intro step. This is a double sided circuit. I tried using pre-drilled single sided prototyping PCB for this step in my previous version but that was extremely difficult to solder. I find double sided to be the best option as the ribbon cable wires emerge at the top side while female header pins emerge at the bottom side.

First solder the 6 vias in the PCB which are providing connection between top and bottom layers. Put a thin bare wire through the vias, solder it at both ends and snip off the excess wire.

Cut off 2 3-pin female headers and stick them together so they form a 3x2 female connector. Now place it on top side and solder it's pins on the bottom side. Finally, bring the wires from ribbon cable emerging from the bottom of mini tic-tac and solder them the same way they went into the main board. Insert the pink striped wire into the hole with the dot(MISO) and the next one in VCC, then SCK and so on.

Notice this is a mirror image of the layout of these pins in the main board. This is because these female headers will connect to male headers on board and need to be mirrored so they align properly.

Just glue the ISCP connector PCB to the bottom of mini-tic-tac box and we're done!

Step 12: Program Away!

Give yourself a pat on the back for doing such a fine work and pop a few mints as a reward if you still have some left. :-)

You can see a close-up of the old and new version's ICSP connectors. The old one was compact but the header was on the bottom of the big tic-tac box and so the PCB couldn't be slid out for repairs without snipping the wires connecting header with board ISP pins. Also, the big enclosure would sometimes not let the male and female headers to interact properly due to tall vertical components on some boards. The whole weight of the programmer also bore down on the connector and slight movement of USB wire caused it to jiggle.

Try it out and program arduino codes onto stand-alone AVR ICs using this to make cheap and simple bare-bones Arduinos for your projects. Or you can put a fresh AVR into your Arduino and program it using Arduino's built in ICSP headers with this. Have fun programming!

Thanks to catlinsdad for motivating me to make my first Instructable...

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