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I am become yak, destroyer of progress.

I was playing with one of my left-over populated Radio 1 boards. I’ve recently gotten a USBasp (knock-off) from eBay and back when I was designing the board I actually thought ahead. I put a standard 6-pin programming header on the board, even though I was just using a Bus Pirate to flash them.

I wasn’t sure what state the fuses and firmware were in, so I read them with avrdude and plugged them into an online fuse calculator. That’s when I saw you can actually clock these down to 128KHz on the internal RC oscillator. Interesting! The board was running a version of the Arduino blink sketch anyway - how slow is 128KHz? So, I set the fuses to find out:

% avrdude -c usbasp-clone -p m328p -U lfuse:w:0xe3:m
avrdude: warning: cannot set sck period. please check for usbasp firmware update.
avrdude: AVR device initialized and ready to accept instructions
avrdude: writing lfuse (1 bytes)

(Check out that warning: it’s going to be relevant in a minute).

Cool, so at this rate it takes an age to flash the LED. I’m not sure what I was expecting. I’ll just put it back how it was:

% avrdude -c usbasp-clone -p m328p -U lfuse:w:0xe2:m
avrdude: warning: cannot set sck period. please check for usbasp firmware update.
avrdude: error: program enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

Ruh-roh.

The 328 is now clocked too slow to speak SPI at the default rate, so I can’t flash it back. The USBasp is running too old a firmware to slow down its clock. Now to begin “a game of programmers”.

I need to use the USBasp to program a Boarduino with the Arduino firmware (it previously had its Arduino bootloader wiped):

Then I use the FTDI to put the ArduinoISP sketch on the Boarduino, and upload new firmware onto the USBasp:

% avrdude -c avrisp -p m8 -P /dev/ttyUSB0 -b 19200
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.02s
avrdude: Device signature = 0x1e9307 (probably m8)

Now I can use the USBasp to fix the Radio 1 board:

% avrdude -c usbasp -p m328p -U lfuse:w:0xe2:m -B 1000
avrdude: set SCK frequency to 1000 Hz
avrdude: AVR device initialized and ready to accept instructions
avrdude: writing lfuse (1 bytes):

Success! Now I’m back at the beginning!

Well, while I’ve got all this kata in my head, I might as well put the Arduino bootloader back on some other knock-offs:

Right, now I can get some work done. Oh. It’s dark out. Maybe tomorrow.