Idea for a "little" mod to the bootstrap code.

[Artie2]

This has probably happened to many of you more than once. You develop this really cool circuit design for the 08M . . . but you need one more input. Just one. Maybe just an interrupt.

So . . . I wonder if this would be possible. As it is now, the bootloader software is constantly on the look-out, (on pin 2), for a serial input. I assume its done through an interrupt. It checks to see if it was a proper download code, and if so, accepts the download from the host computer. If it isn't, it resumes wherever it was interrupted from.

What if . . . instead of doing nothing if the code was something else, it just sets a special internal variable. Or, better yet, just passes the interrupt along to the current program. It would be a special interrupt. You wouldn't need to check to see what the data was. Just the fact that "something" happened was all you need. Like an external "trigger" of sorts. You could use that input to sense for some external event, and then send your code into action, without needing to use any of your 5 I/O's.

It seems like a simple mod to the bootstrap code could do this. Maybe.

 

[hippy]

That would not be an easy change to make and would not work well in practice. The download detect does not work as an interrupt; if the PICAXE thinks it sees a download then determines there was not it restarts from the beginning of program rather than where it was. This is why it is essential to fit the download interface.

If you need more I/O the best option is to use a 14M or 20M

One useful trick is to design circuits for a 14M or 20M but only use the legs which would be available when an 08/08M is plugged into the top of the socket.

 

[Artie2]

Ah . . . I figured there'ld be a catch. Thanks Hippy.

Then again, generating a program restart, could be useful in itself.

 

[womai]

Another issue I can see with that is that it could easily make a Picaxe unresponsive to downloads, so it would have to be reset manually just before the download attempt. That can already happen now during e.g. sleep commands and frequently causes confusion with beginners.