 |
| Click on the image for an annotated version. |
Add the link wires
Begin populating the board with the link wires. Most of the link wires can be safely made with uninsulated wire if you are careful and keep the wire taught and straight. Wires which run closer than 0.1" spacing should be insulated - see the photographs on Flickr. Don't fit any wires to the underside of the board at this time. I colour-coded the wires in the Fritzing layout:
| Colour | Meaning |
|---|---|
| Red | +Vcc (digital and analogue) |
| Green | Ground (0V) |
| Yellow | Reset |
| Blue | Miscellaneous, can be uninsulated |
| White | Connect on underside (or under IC socket if possible) |
| Brown | Insulate due to length |
Add the remaining components
Add the remaining components, except for 1N4001 diode, starting with the lowest ones first. Some of the decoupling capacitors are fitted inside the IC socket; keep the leads short so that they do not stop the microprocessor from being inserted. Align the IC socket so that the notch indicates pin 1 end. Ensure that the metal can of the crystal does not touch any of the surrounding wires. Add the ISP header and solder the wires to the underside of the board.
Finally add the headers. Remember that the D8-D13 header is an offset header. I found it easiest to use an ethernet shield to hold the headers at the correct spacing.
Test the board
Before inserting the microprocessor test all of the connections. Then add the FTDI cable/breakout board and power the board from USB. The red LED should light indicating that power is applied. Then check that +5V power is applied to the correct locations of the IC (pins 10 and 30). Check that the GND connections are good (pins 11 and 31). Now add the reverse protection diode; if the polarity of the power supply is reversed the diode will conduct and trip out the polyfuse.
Insert the microprocessor, taking care to get the correct orientation. There's several possible options, see this feature comparison to select the most appropriate one. If you are intending to upload sketches via USB you will need to add a bootloader to the microprocessor. (To be covered in a later post).
Use the blink sketch to test the board. If everything is ok it should just work (it did for me).
Resources
Further photos are available on Flickr. The Fritzing files are on GitHub.
Bill of materials
| Quantity | Item | Order code |
|---|---|---|
| 1 | ATmega164P, ATmega324P, ATmega644P or ATmega1284P | |
| 1 | MCP1702 LDO 3V regulator | |
| 1 | 2N7000 FET | |
| 1 | red LED (3 or 5mm) | |
| 1 | green LED (3 or 5mm) | |
| 1 | 1N4001 diode | |
| 1 | RXEF025 500mA polyfuse | Onecall 1175860 Sparkfun COM-08357 |
| 1 | 16MHz crystal, 18pF load capacitance, HC49 case | |
| 2 | 22pF ceramic capacitor | |
| 6 | 100nF ceramic capacitor | |
| 1 | 100µF electrolytic capacitor, 16V | |
| 2 | 1kΩ resistor, 0.25W | |
| 1 | 10kΩ resistor, 0.25W | |
| 1 | SPST switch | Onecall 1813689 Sparkfun COM-00097 |
| 1 | 40 pin 0.6" IC socket | Onecall 4285669 Sparkfun PRT-07944 |
| 1 | 4 pin stackable header | Protopic PP4PSHF |
| 1 | 6 pin stackable header | Sparkfun PRT-09280 |
| 3 | 8 pin stackable header | Sparkfun PRT-09279 |
| 1 | 8 pin offset stackable header | Sparkfun PRT-09374 |
| 2 | 3 pin 0.1" header (male) | |
| 1 | 2×3 pin 0.1" header (male) | |
| 1 | Break-away headers, straight | Sparkfun PRT-00116 |
| 1 | Break-away headers, long | Sparkfun PRT-10158 |
| 1 | Break-away headers, right-angle | Sparkfun PRT-00553 |
| 4 | 2 pin jumper | Sparkfun PRT-09044 |
| 1 | stripboard, 38 strips, 30 holes long | |
| wire, 22AWG |
