Homebrew PCBs

Andrew wrote:
>>The guy from victoria wrote:
>>
>>A terminal program just dumps files from
>>the pc into the machine, which is no
>>different if tiff or g-code is used.
> 
> 
> Well - In this application g-code is not
> suitable.  If you remember the start of the
> thread - I am trying to make a cheap
> photoplotter anyone can replicate for a few
> $100 or so.
> 
> Drum photoplotter means raster.
> 
> Cheap means that I cant have enough CPU and
> RAM onboard to convert vector to raster
> internally.
> 
> The board is planing on having an ATMEL,
> a analog PLL and not much else on it.
> 
> 16 megahertz - 8 bit CPU
> 128K ROM
> 16K RAM
> couple of timers
> a UART
> and an SPI port.
> 
> Call me a masochist I guess :D

I got slightly confused thinking of EDM machines.

At the data rates needed, you'll need to store the
whole file in the machine controller.

A 300mm drum has a circumference around 1000mm.

Assume a pixel size of 0.01mm.

If it rotates at 600rpm, the pixel rate is 1Mpixel/sec.

A 100mm x 100mm plot will need 1000s or 17mins to scan.

The averaged pixel rate will be 100k pixels/sec.

The file size will be 100Meg pixels, which is impractical.

You'll need to transfer and store the file in a vector
format, and progressively rasterize it as the drum scanner
needs it. If you rasterize to 1k pixels at a time, you'll
only need to do that 100 times per second.