pic bootloaders

the tiny pic bootloader page lists a number of other bootloaders. i haven't looked at all of them in detail, but it sounds like zpl might be the best one for me. it's not much bigger than the tiny bl, and it requires no modification of the bootloaded hex. i think it can even use hexes written to use other bootloaders, but i'd have to try that to be sure. the interface hardware is really simple (3 resistors, one transistor, and an optional led). other than vdd and vss, it only connects to /mclr. so it doesn't use _any_ i/o pins and can be left in while the pic is running. the front end is in python (with pyserial) so it's multiplatform. i just had to change 'import serial' to 'import serial.serialposix as serial' in zpl.py and delete the non-functional serial.py that comes with it so it would use my built-in pyserial. one downside is that the communication is one-way; there is no way to verify the reprogramming. there is an option to rewrite the hex a given number of times, as a quick fix in a noisy situation. given the way it works, it might also be quite a bit slower but i'll have to check that. the bootloader won't overwrite itself, nor will it change the fuses (even though the pic could do either). so fuse configuration changes and changes in clock frequency will need the old jdm2 with the vpp sledgehammer, but at least zpl will never kill itself. for quick dev/debug iterations without big changes to the circuit, this bootloader should be ideal.