Note: this reflects the state of the system on 2018-01-20. If you want to check out code that behaves the way this document describes, I suggest checking out the commit where this doc was last modified.
On the Icoboard with an SD card, BsForth can recompile itself. You can make changes at any level of the BsForth stack, produce a new system image, and reboot into it, all without needing a separate computer. (Though you'll want to have one handy for when you bork your Flash.)
The process is a little labor intensive at the moment. Here it is.
First, you'll need to get BsForth running on CFM on the Icoboard, as described in the Icoboard directions.
You will also need an SD card. Currently it must be 2GiB or smaller. It doesn't matter how much smaller -- we'll only use about 300 kiB. I use an old 32 MiB card I found.
Next, we'll need to convert some of the BsForth sources into packed Forth block
format, and write them onto an SD card. I'll assume your SD card is /dev/sdg
here. Note that this will destroy whatever data is currently on the SD card.
$ make build/bf-ico.fblocks build/meta.fblocks
$ dd if=/dev/zero of=/dev/sdg bs=1024 count=300
$ dd if=build/meta.fblocks of=/dev/sdg bs=1024
$ dd if=build/bf-ico.fblocks of=/dev/sdg bs=1024 seek=99
$ sync # for good measure
Your SD card now contains the BsForth bootstrapper (Forth version) starting at block 1 (physical block 0) and the BsForth sources corresponding to your checkout starting at block 100 (physical block 99).
Insert the SD card into the CFM.
At the BsForth prompt, type the following to load the bootstrapper:
1 25 thru
(The precise range will depend on the size of the bootstrapper sources you're using.)
This should take around two seconds, and respond with ok. Now:
begin-bootstrap 100 199 <thru> end-bootstrap
This should list the blocks as they are consumed until finally printing the
number of bytes used in the target, after about five seconds. (The number of
bytes printed should exactly match the size of the file generated by make build/bf-ico.hbin on your big computer.)
At this point you could test the system by running
reboot-into
Or you could load my dev toolset and program the image into SPI flash, so that it gets used on the next reset:
xxx 2 over + swap 4 + thru \ xxx is the base block of extras.fs
<save>