All of the examples are "shared memory", including the initial code
(which used shared memory and interrupts).  "Shared memory" in this
case meaning memory that both the ARM core and the PRU core have
read/write access to.

If the links William provided aren't what you are looking for, be a
bit more specific about your question and it will be easier to help you.

On 10/14/2016 11:10 AM, William Hermans wrote:
> My mistake, I think the second link I gave is an explanation of the PRU 
> shared 
> memory and not DDR shared memory. So, if you do a google search for 
> "beaglebone 
> pru shared ddr memory" there are lots of hits out there. You're bound to find 
> something that makes things understandable.
> 
> On Fri, Oct 14, 2016 at 8:48 AM, William Hermans <yyrk...@gmail.com 
> <mailto:yyrk...@gmail.com>> wrote:
> 
>         awesome!  Thank you!  Do you know where I can find a good example of
>         using shared memory?  I am wondering if I might be better off using
>         shared memory instead.  Does shared memory work both ways so that ARM
>         can access the PRU memory and PRU access the ARM memory?
> 
> 
>     There is a DDR example here:
>     
> https://github.com/beagleboard/am335x_pru_package/tree/master/pru_sw/example_apps/PRU_memAccess_DDR_PRUsharedRAM
>     
> <https://github.com/beagleboard/am335x_pru_package/tree/master/pru_sw/example_apps/PRU_memAccess_DDR_PRUsharedRAM>
> 
> 
>     Then if you need a better explanation of the code( Like I would ). You can
>     read this:
>     
> http://www.embedded-things.com/bbb/understanding-bbb-pru-shared-memory-access/
>     
> <http://www.embedded-things.com/bbb/understanding-bbb-pru-shared-memory-access/>
> 
>     On Fri, Oct 14, 2016 at 4:36 AM, Jay Doobie <doobi...@gmail.com
>     <mailto:doobi...@gmail.com>> wrote:
> 
>         awesome!  Thank you!  Do you know where I can find a good example of
>         using shared memory?  I am wondering if I might be better off using
>         shared memory instead.  Does shared memory work both ways so that ARM
>         can access the PRU memory and PRU access the ARM memory?
> 
> 
>         On Thursday, October 13, 2016 at 10:59:26 PM UTC-4, Charles 
> Steinkuehler
>         wrote:
> 
>             On 10/13/2016 5:48 PM, Jay Doobie wrote:
>              > Hi,
>              >
>              > I'm trying to send some data from ARM to the PRU for the PRU to
>             execute upon it,
>              > but I'm having some issues where it tends to miss some of the
>             data on the PRU,
>              > so I assume I am not synchronizing the interrupts properly, 
> here
>             is basically
>              > what I am doing:
>              >
>              > C code:
>              >
>              >     for (i = 0; i < 10; i++) {
>              >       prussdrv_pru_write_memory(PRUSS0_PRU0_DATARAM,
>             SHARED_MEMORY, (unsigned
>              >     int*)pkts[i], memSize);
>              >        //if I put a sleep here it generally works: 
> usleep(500000);
> 
>             The ARM has a weak memory model.  You need a memory fence 
> instruction
>             here to insure that all writes before the fence (your write to 
> the PRU
>             memory, above) have completed before any writes after the fence
>             (generating the PRU interrupt) take effect.
> 
>             It's a bit ham-fisted, but you can use a __sync_synchronize() here
>             (assuming you're using gcc...it's a full memory barrier).  Or you 
> can
>             use the C++11 memory fence semantics (more complicated).  Either 
> is
>             way better than the "old school" full cache flush and invalidate! 
>  :)
> 
>              >        //printf("sending intc...\n");
>              >        // here are the packets!
>              >        prussdrv_pru_send_event(ARM_PRU0_INTERRUPT);
>              >        // wait for PRU response
>              >        //printf("waiting intc...\n");
>              >        prussdrv_pru_wait_event (PRU_EVTOUT_0);
>              >        // clear PRU response
>              >        //printf("clr intc from PRU0...\n");
>              >        prussdrv_pru_clear_event (PRU_EVTOUT_0, 
> PRU0_ARM_INTERRUPT);
>              >
>              >   }
>              >
>              >   PRU:
>              >
>              >     HANDLE_DATA:
>              >         // wait for interrupt
>              >         WBS r31, #30
>              >         // reset interrupt
>              >         LBCO    r20, CONST_IEP, 0x44, 4      // Load CMP_STATUS
>             register
>              >         sbco rResetInterrupt, CONST_PRUSSINTC, SICR_OFFSET, 4
>              >         // handle data
>              >         MOV       R31.b0, PRU0_R31_VEC_VALID | PRU_EVTOUT_0
>              >         sub rCounter, rCounter, rCounter
>              >         qbne HANDLE_DATA, rCounter, 0
>              >
>              >
>              > Kernel: Linux beaglebone 3.8.13-bone79 #1 SMP Tue Oct 13 
> 20:44:55
>             UTC 2015
>              > armv7l GNU/Linux
>              >
>              > Thanks!
> 
> 
> 
>             -- 
>             Charles Steinkuehler
>             cha...@steinkuehler.net
> 
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-- 
Charles Steinkuehler
char...@steinkuehler.net

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