In the course of the design for the Standalone Sleepduino, I needed to create a bare-bones breadboard that could run an Arduino sketch. I really mean bare bones, too: I didn’t even want to include the 16MHz crystal, as through-hole versions take up too much room and surface-mount versions are a pain (as I found when I got hold of a pair of Texas Instruments LaunchPads, but I digress.)
I snagged myself an ‘Arduino compatible component kit‘ from the lovely guys at Oomlout, which included all the parts I didn’t really need but wanted on hand just in case alongside the most important part of the kit: the ATMega328 microcontroller itself.
Sticking it in a breadboard, I followed the official instructions on how to burn an Arduino bootloader onto an ATMega328 so that it uses its internal 8MHz oscillator instead of an external crystal as its clock source.
At least, I tried to.
I spent about an hour wrestling with one major problem:
avrdude: Expected signature for ATMEGA328P is 1E 95 0F
Double check chip, or use -F to override this check.
Every single time I tried to program the 8MHz bootloader, avrdude told me to -F off. Eventually, I twigged what was going on: official Arduinos have an ATMega328P-PU chip, which you can see printed on top. In good light. If you squint a bit. My chip?
One little letter, so much heartache. While the ATMega328P and ATMega328 microcontrollers are pretty much interchangeable, they have different signatures. The version of avrdude that ships with the Arduino IDE knows about ATMega328Ps, but not about ATMega328s. Hence my problem.
Thankfully, there’s a fix. To load an Arduino bootloader onto an ATMega328, open up avrdude.conf (found in /usr/share/arduino/hardware/tools/ on Linux boxes) and search for the string “0x1e 0x95 0x0F”. That’s the signature of an ATMega328P. Replace it with “0x1e 0x95 0x14”, which is the string of an ATMega328 and save the file. If you’re on Linux, you’ll need to be root to save the file. Restart the Arduino IDE, and you should be able to burn the bootloader without any errors.
When you’re done, remember to replace “0x1e 0x95 0x14” with “0x1e 0x95 0x0F” again, or you’ll get a bunch of messages telling you that only assembler is supported…
UPDATE: While this all still works, compiling sketches for the thing is broken as of Arduino 1.0.0. To fix, you need to copy a file into a certain directory. On Linux, it’s a case of:
sudo cp /usr/share/arduino/hardware/arduino/variants/standard/pins_arduino.h /usr/share/arduino/hardware/arduino/cores/arduino/
That should fire things back into life.