Homebrew PCBs

On 13. 12. 2014 11:39, 'Tony Smith' ajsmith1968@... 
[Homebrew_PCBs] wrote:
> At 1,000 DPI, the laser isn't going to be anywhere near it's supposed to be
> anyway.  Close enough thought.
>
> The beam of the laser will be probably bigger than a dot a 1,000 DPI (which
> is good as the overlap fills in the gaps) depending on a bunch of things.
>
> Dunno how LinuxCNC does rastering, but often the laser is left on between
> dots so that evens things out.  Sometimes you want dot - dot - dot lasering,
> but not in this case.
>
> Tony
>

The laser dot is just little under 1000dpi in size. But I have limited 
on off timings so the width I can controll is about 700DPI. But this is 
true only for rotation axis. I advance board for only 0.01mm each 
revolution so there are plenty of overlap. And I do leave laser on if 
there are more same dots in a row.

My preprocesor program just crunch the coordinates and make file stream 
of '1' and '0' for laser for each 15us. The linuxcnc with component 
'streamer' then stream this each 15us to the laser. And here is 
bottleneck as I can't go faster (but I want) and I need to make some 
special hardware to stream much faster than 15us/pulse.

I think to use some AVR with plenty of ram and to upload entire stream 
on it, and after that just stream bits. At 1 bit per 1us the AVR will 
work hard. But seems that static ram is just too small to fit entire 
image, I will probably use dinamyc ram (4Mbits *4). As I calculated I 
don't need to worry about refresh as cycling as streaming is fast 
enought to keep memory refreshed. But need to cary refresh when data is 
uploading and waiting start of operation where is enought time to proper 
manage refresh cycle.