Friday, June 13, 2008


PIC file release

I've just done release v1.2 of the PIC firmware. Get it here.

There are three files in this release:

These do as they say - you can either half-step or full-step the
motors. Half stepping is more precise, but slower; full the opposite.
There is a problem with integer overflow for tall objects (> ~50mm) if
you half-step the Z motors. The third file allows precise XY, and
also allows Z to go to about 100 mm. Precision is not needed for Z as
it uses a screw drive anyway.

This version of the firmware will drive a solenoid valve in addition
to the heater, extruder motor and cooling fan.

THE FAN NOW WORKS OFF RB6, not the spare channel of the L298. That
channel is used to drive the solenoid.

To drive the fan, wire in a TIP110 to ALT 2 (or ALT 1), connect in the
end of the 220 ohm resistor that goes to the base of that transistor,
but connect the other end to hole 4 on the 7-hole connector by the
Max/Empty connector. This goes to RB6. It's probably a good idea to
wire a diode across connector P7 so that it's reverse biased (stripe
to the +12v line, in other words); that'll take care of any back EMF
from the fan motor.

The code is now compatible with the Arduino, and the latest Java host
software is set up to drive it too.

As we are now switching to the Arduino, this is probably the last PIC file release that we will do.

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