The Arduino Burner Shield

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Arduino Burner PCB

Arduino Burner PCBContinuing my creation of circuits that save me a little time, I’ve developed a shield which turns an Arduino Duemilanove (or compatible) into an EPROM burner for ATMega328 chips. Imaginative as ever, I call it the “Arduino Burner.”

While working on the Standalone Sleepduino, I had cause to burn a custom bootloader to an ATMega328 chip in order to convince it to use its internal 8MHz oscillator instead of an external 16MHz crystal. With an Arduino Duemilanove, that’s not too difficult: follow the instructions from the Arduino To Breadboard article and you’re away.

It does, however, require a bit of time to set up the various wires; then more time is required moving the wires to upload a sketch to the newly-created Arduino-compatible microcontroller. Not much time, to be fair, but time nevertheless. So, the Arduino Burner was born.

The Arduino Burner is a simple shield based on the wiring from the Arduino To Breadboard article. It features room for a 16MHz crystal and decoupling capacitors, although these can be safely ignored if you’re programming an ATMega using the 8MHz breadboard bootloader. Installing them does, however, mean that you have the choice of flashing either bootloader; leaving the holes unpopulated means that you’ll be limited to the 8MHz version only. There’s also a 10K pullup resistor for the reset line, although again this is a ‘nice to have’ that can be ignored.

Usage is simple: stick a raw ATMega328 into the zero insertion force (ZIF) socket in the middle of the shield, set J1 to ‘BTLDR’ and open the RX and TX jumpers and you can burn a bootloader straight from the Arduino IDE. When your bootloader is installed, you can close the RX and TX jumpers and switch J1 to ‘SKETCH’ to upload a sketch – but remember to remove the Arduino’s own ATMega, or you’ll be uploading the sketch to that instead of your new chip!

The ZIF socket means that the legs of the ATMega328 are protected from damage – a key point if you’re burning large quantities of chips. It does, however, increase the cost of the shield quite significantly: a single 28W DIP socket is around 20p, while the particular low-profile ZIF chosen for this shield is around £8 – although this does drop as you buy quantities.

If you’re only creating one-off standalone projects, the Arduino Burner shield is overkill. If you’re doing large quantities and don’t fancy shelling out for a real AVR, however, it can be a serious time-saver.

I’ll be getting a prototype made up towards the end of the month, so pop back then if you want to see the shield in action.

Using an ATMega328 as an Arduino

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Arduino Duemilanove Side View

Arduino Duemilanove Side ViewIn 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?

An ATMega328-PU.

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.