firmware
code: joe lake, brian crabtree
image: usb jtag love.
we’re using a usb avr ice from sparkfun. using jtag we develop using avrlibc, gcc, and avarice on os x (also works great on linux).
there is no bootloader, and the jtag port is on the pcb. the ftdi chip is serialized to have a better device name.
the code is available here on the site. there are some additional ports and pads on the board which we made available for analog level reading, but we’d also like to see people re-purpose it to read other sensors (like an optical encoder).
the ft245r and atmega32 are connected via an 8 bit bus. this is a wonderful in that the system is baud-rate independent. the fifo has huge buffers in both directions so the code is very easy to implement. there’s a pinout diagram available on the wiki.
the simple protocol is contained in two-byte packets. it’s also on the wiki.