Minimalduino v.89 Delivered

Three copies of my latest Minimalduino design (V .89) arrived today, fabricated in the DorkbotPDX circuit board order. I built one with all components and it works perfectly, with the exception of the 3.3V regulator having a different pinout than the 75LXX part I used in Eagle-- oops...

A SparkFun protoshield and Adafruit motor shield fit on top fine, but with very little (read: "zero") clearance over the tall capacitors I used-- they'll get some tape on top, and the next revision will use shorter caps or orient them sideways. Excited to work with my first factory-made board, I shot and posted some build pictures with a few notes.

To correct in the next revision:

• Fix 3.3V regulator (MCP1700-330) pinout,
• Lay out for wider/shorter or horizontal voltage regulator caps for better shield vertical clearance.

To add/improve in the next revision:

• 5V/3.3V switchable with a jumper on three pins (though it will limit power),
• Top pad and through holes under 7805 for better heat dissipation,
• Credits (CC, author names) on bottom silk screen,
• Optional resettable fuse?
• Optional on/off switch or jumper pins?
• Try to reduce the number and length of jumpers.

Minimal Arduino?

I prefer breadboard-friendly Arduino-compatible boards like Boarduino and iDuino, but I keep wanting functionality people have built into shields like Adafruit's Motor Shield and Batsocks' TellyMate Shield.

All I want in an Arduino:

• ATmega328
• FTDI programming header
• Arduino "form factor" with odd D7/D8 spacing and standoff holes

Sorting my Arduino-compatible board spreadsheet first by price, then by form factor, it seems the lowest price for a shield-compatible board is ~$17 for a serial Freeduino, compared to ~$10 for a Dorkboard, though the latter comes with an ATmega168, not a 328.

Necessary items:

• microcontroller: ATmega328, socket, capacitor
• clock: oscillator and 2 caps, or a resonator
• reset: 90-degree (side) button, 10K resistor
• FTDI cable interface: 6-pin header, capacitor
• Power: Barrel connector, 2-pin header

Extra interface header pin pads:

• icsp (2x3)
• i2c (4)
• spi (6) (nah)

Simple extras, parts not provided:

• Power indicator: LED, 1K resistor
• TX/RX indicators: 2 more LEDs, 2 more 1K resistors
• Power regulation: 7805, 2 capacitors, jumper
• Diode to prevent inverted power hookup

I'm traveling for the next month so this will be a fun little layout project, perhaps as a way to learn kicad (as opposed to EAGLE, which I currently use) and to explore board house pricing and specs. The goal is to be able to produce a $10 kit (cost), which may be possible given how many goodies SparkFun includes in their $20 Arduino Pro 328.

Update 12/29: I got a single-sided board laid out with just four jumpers, and I'll tear it up and redo it with the programming header where I want it, jumping TX and RX across the board. The files for the "Severino" single-sided board helped me figure out the routing.