Thu Jun 26 14:58:17 CEST 2008

chip bootstrap and monitor protocol

The problem with CATkit is that it needs a bootstrapped chip that
listens for commands on the serial port. The problem with this is that
there is a threshold for people to start using Purrr for PIC18 without
buying a programmer: they have to build one. It would be a lot more
convenient to do all the communication throug the ICD port.

In theory this isn't so difficult, but does require some juggling to
get going. The Purrr console is an RPC protocol: host sends command to
target and waits for reply. The Microchip debugger protocol is a
master-slave protocol. After bootstrapping using the one-way Microchip
programming protocol the PIC can be made to do anything, but requiring
the host to wait for asynchronous replies isn't so easy to do with
custom hardware.

I was thinking about a serial port based interface in which the target
-> host protocol is simple RS232, but host->target can be synchronous
(for initial programming) or asynchronous.