DMA examples

QNX Newsgroups (Archives) qdn.public.qnxrtp.embedded
1

I have an application where I need to write data to memory
from a file, and then rapidly read that data back and write it
to a couple of D/A converters to control a couple of
galvanometers. My thought was to use DMA transfers
to accomplish this.

Can anyone provide information or examples showing:
How reserve and map to a chunk of memory for DMA purposes
How to access it
etc?

thanks!

Bruce Gilland

2

Use mmap() for creating contigious memory and use mem_offset() for getting
the physical address of this memory. For mapping physical memory (like
device memory) into virtual memory use mmap_device_memory()

–
Jens

Look at mmap_device_memory() for
<gilland@cs.colorado.edu> wrote in message
news:3d135773.9625721@inn.qnx.com…

I have an application where I need to write data to memory
from a file, and then rapidly read that data back and write it
to a couple of D/A converters to control a couple of
galvanometers. My thought was to use DMA transfers
to accomplish this.

Can anyone provide information or examples showing:
How reserve and map to a chunk of memory for DMA purposes
How to access it
etc?

thanks!

Bruce Gilland