[En-Nut-Discussion] Nut OS reliable on AT91SAM7X Evaluation Board?

[Ulrich Prinz]

Hi Ole,

Ole Reinhardt schrieb:
> Hi Ulrich,
> 
  > Background memcopy won't work, as the PDC does not support
> memory<->memory dma.
The data sheet is a bit unclear in that point, but I figured out that is 
doesn't work too. Doesn't harm the actual application. IN most cases 90% 
of the buffer content needs to be created or modified and instead of 
writing it back I can write it to the new position as well.
> 
> And always keep in mind the overhead for the pdc. Especial with the SPI
> I implemented PDC for the SPI function and these became notably slower
> as polling mode when just sending small data packets. 
> 
Yes, that's an important point. I didn't mention that as it was obvious 
that is doesn't make sense to preset 10 registers if you have to send 
out only two bytes.

> Having both possibilities and an automatic decision which of them to use
> would be nice. 

Hihi, with my radio driver I was experimenting on that. I first need to 
send out 2 bytes for the chipset to set it to the right mode, then I 
have to send the complete radio packet. So I tried a double buffer DMA, 
programming the first page for 2 bytes of the command and the second 
pointer pair points to the data buffer.

But I didn't get it to work, as I had not enough time to figure out how 
to enable the PDC support or what to do with these pipes mentioned in 
the PDC driver version. I'll keep on as I have time.

Regards, Ulrich