EBB Firmware: Add long ints (4 bytes) for step counts

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From a user request: for any command that take a number of steps, use 4-byte 
signed values rather than 2-byte signed values to give the ability for very 
long moves. The move time would also have to be extended as well.

Original issue reported on code.google.com by brian.schmalz on 9 May 2011 at 9:53

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Note that after several false starts, this turns out to be more complicated 
than it seemed at first. There are several math operations that are currently 
performed at 2x the width of the step and duration parameters. This means that 
that if we extended duration and steps to 4 bytes (which the C18 compiler 
supports) we would need to do 64 bit (8 byte) math which C18 does not support.

I need to check to see if XC8 supports 64 bit math, and if so try to convert 
the code base over to XC8 (which I have tried in the past, but was not trivial) 
to see if that might be an easy way forward.

Original comment by brian.schmalz on 26 Apr 2014 at 11:18

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Original comment by brian.schmalz on 26 Apr 2014 at 11:18

• Added labels: EBB

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OK, so 4 byte long values was actually too much work. So I went with 3 bytes 
values. As of version 2.2.5, the <duration> and <Axis1> and <Asix2> values can 
be up to 3 bytes each now. (<duration> is unsigned, <Axis1> and <Axis2> are 
signed.) That still gives a maximum of about 4.7 hours for one move, with up to 
8388607 steps per move.

I've also implemented checks to make sure that you don't try to have a step 
rate that's too slow in either axis. The slowest that the EBB can do is 0.76Hz. 
This (and the check for > 25Khz) are not _exact_, as the math isn't easy unless 
we add in floating point support, which I'd rather not do. But it gets the job 
done.

Original comment by brian.schmalz on 30 Apr 2014 at 6:58

• Changed state: Fixed