BeeCNC Motherboard v1

I’m still working on the BeeCNC. Yesterday I laid out a PCB in gEDA PCB and etched it with Ferric Chloride. It’s based on the Arduino designs, uses a 28-DIP ATmega chip, and employs three Sparkfun/Schmalzhaus EasyDriver stepper driver chips.

Today I worked awhile to burn the bootloader onto the chip, but I ran into some trouble. I am using ladyada’s USBtinyISP for programming with avrdude as the software.

I plugged the USBtinyISP into the header, applied 5V regulated power to the circuit (no power jumper in place on the USBtinyISP) and ran:

sudo su
root@travis-macbook:/home/travis# avrdude -p m168 -c usbtiny

The output at first seems okay:

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.01s

avrdude: Device signature = 0x1e9406

avrdude: safemode: Fuses OK

avrdude done.  Thank you.

After that output, without touching the circuit, I run the same command again:

root@travis-macbook:/home/travis# avrdude -p m168 -c usbtiny

The output is unexpected:

avrdude: initialization failed, rc=-1
 Double check connections and try again, or use -F to override
 this check.

avrdude done.  Thank you.

I don’t understand why the ISP works fine the first time and then doesn’t work immediately afterwards. Restarting the computer allows avrdude to work again, but only once (then another restart, etc).

I’ve posted the problem in the adafruit forums, and will update with progress.

UPDATE: The problem was a short to one of the oscillator pins.

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