Fwiw. you can simply place "upgrade" files on microSD.
The write protected bootloader I mentioned earlier is my own. It will load and flash the upgrades to Cortex M4 flashram and to the ESP8266 spiflash from microSD (fat32) on powerup.
Personally I use the cpcxfer program I put on github which is much quicker than using jtag or swd and if the wifi crashes you put it on microsd manually (or get a cheap st-link clone).
xfer -u
10.0.0.37 M4FIRM.BIN / 0 (upload firmware)
xfer -r
10.0.0.37 (reset M4 and reload it)
There is many other uses for this board if someone feels like it and want to explore it, I am limited by the choice of doing romboard emulation and few I/O ports, which requires very precise timing and litterally counting instruction clock cycles, when edges are triggered.
Should it be used as a proper accelerater for the CPC itself, instead of rom emulation, you'd do ram emulation and manipulation. Which I believe is possible in similar way to rom emulation.
I have not protected anything (which would have been super easy) and everything is in plain text so any uses are obviously welcome (on own risk etc). and if someone wants to know how the gpio is configured (which is all you need to know) just pm me.
There is a lot you don't know about me. I'm an Atmel programmer too (see CPC Booster f.e.). But I don't have a JTAG programmer.[nb]There is nice software for PC to target all this systems, and if the hardware has an 'update' function, then no need to buy hardware like an expensive JTAG programmer. Have you ever heart of Ponyprog for ATMega16/32? Did you know that you can use the next higher MPU in CPC Booster easily and have double ROM?[/nb]