Hello,
Since I'm new to this forum, I will introduce myself. I'm C/C++ software
engineer and have experience with, among other things, Atmel AVR and SAM
(Cortex) . Recently I started playing with embedded Linux (Raspberry Pi
and Beaglebone Black) as a hobby project. My goal is to develop a DCC
<https://www.nmra.org/index-nmra-standards-and-recommended-practices>Central
using the Beaglebone Black platform.
I'm using Code Composer Studio V7 (on Windows) to write, compile and debug
code on the BBB (for the pru using a Blackhawk USB100v2 JTAG emulator). On
the BBB I flashed the latest IoT release :
debian@beaglebone:~$ uname -a
Linux beaglebone 4.4.84-ti-r120 #1 SMP Sun Aug 27 03:11:07 UTC 2017 armv7l
GNU/Linux
debian@beaglebone:~$ cat /etc/dogtag
BeagleBoard.org Debian Image 2017-08-24
debian@beaglebone:~$
The BBB is plugged in a Newhaven 7" LCD cape (functional in character
mode), but I cannot see the cape loaded :
debian@beaglebone:~$ cat /sys/devices/platform/bone_capemgr/slots
0: ---l-- -1
1: ------ -1
2: ---l-- -1
3: ---l-- -1
debian@beaglebone:~$
Since I can compile C code in CCS and debug PRU code on the device, I *think
*the pru's are operational :
debian@beaglebone:~$ lsmod | grep pru
pru_rproc 15879 2
pruss_intc 9009 1 pru_rproc
pruss 12346 1 pru_rproc
debian@beaglebone:~$
Now I'm looking into ways to write a linux app that can communicate with
the PRU firmware. Am I correct in assuming that rpmsg is the way to go ?
After google-ing a lot and reading about the subject, I try to run this
code :
int main(void)
{
struct pru_rpmsg_transport transport;
uint16_t src, dst, len;
volatile uint8_t *status;
/* Allow OCP master port access by the PRU so the PRU can read external
memories */
CT_CFG.SYSCFG_bit.STANDBY_INIT = 0;
/* Clear the status of the PRU-ICSS system event that the ARM will use
to 'kick' us */
CT_INTC.SICR_bit.STS_CLR_IDX = FROM_ARM_HOST;
/* Make sure the Linux drivers are ready for RPMsg communication */
status = &resourceTable.rpmsg_vdev.status;
while (!(*status & VIRTIO_CONFIG_S_DRIVER_OK));
/* Initialize the RPMsg transport structure */
pru_rpmsg_init(&transport, &resourceTable.rpmsg_vring0, &resourceTable.
rpmsg_vring1, TO_ARM_HOST, FROM_ARM_HOST);
/* Create the RPMsg channel between the PRU and ARM user space using
the transport structure. */
while (pru_rpmsg_channel(RPMSG_NS_CREATE, &transport, CHAN_NAME,
CHAN_DESC, CHAN_PORT) != PRU_RPMSG_SUCCESS);
while(1)
{
/* Check bit 30 of register R31 to see if the ARM has kicked us */
if (__R31 & HOST_INT)
{
/* Clear the event status */
CT_INTC.SICR_bit.STS_CLR_IDX = FROM_ARM_HOST;
/* Receive all available messages, multiple messages can be
sent per kick */
while (pru_rpmsg_receive(&transport, &src, &dst, payload, &len)
== PRU_RPMSG_SUCCESS)
{
// Process payload here
/* Echo the message back to the same address from which we
just received */
pru_rpmsg_send(&transport, dst, src, payload, len);
}
}
}
}
However, this sequence loops at while (!(*status &
VIRTIO_CONFIG_S_DRIVER_OK));
I suppose there is some driver missing or not running, but have no idea
which one...
Any help is appreciated !!
Thanks in advance,
Paul
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