Arduino: extension

[mitra42]

Check the extension process works ... this could involve the following steps .... See #70

[mitra42]

• [ ] Try adding the blink code as a single C function
  • [ ] hooked to setup or loop
  • [ ] hooked to a forth word
• [ ] break into a constant and a word to set it on or off etc in forth
• [ ] call that forth as part of boot

• 73 then find http library and add that as an extension (as new issue)

[mitra42]

See #63 for some extensions to manage pin writing, this is effectively an extension mechanism for Arduino and will be improved incrementally.