On 11/26/2016 1:33 PM, Neil Jubinville wrote:
>
> Here is my basic understanding - Focusing on PRU0:
>
> Each PRU has 8K of 'dataram' - This is where I expect R1,R2,R3 ---- R31 to
> be
> stored. *Is this true? I see many people changing the reference at
> *0x0000_0n00,
> n = c24_blk_index[3:0], do I need to set where the Rn's lay down in memory?
NO
The data ram is what it says...data ram. The registers are what they
say...registers. Registers are *NOT* data ram. If you want the
register values to appear in memory, you have to write them out using
the SBBO instruction.
> Docs also state that the PRU 0 Data ram starts at *0x4a300000*;
>
> int registerStart;
> registerStart = *(int*)0x4a300000;
> printf("--> R0 = %d" + registerStart);
>
> However I get a seg fault trying to print what is in R0 that way. That was
> more
> to just do a direct look see if possible and go around all the interfaces.
0x4a300000 is a physical address. You can use that if you are
directly accessing memory (via /dev/mem, bus-mastering DMA, or
something that doesn't use an MMU like the PRU core). If you try to
access a physical address from a standard application that has not
been mapped into your process memory space, the MMU will forbid access
and your program seg-faults.
To access the PRU memory in your application, use the address provided
to you by the prussdrv_map_prumem function.
--
Charles Steinkuehler
[email protected]
--
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