Debian Preparation for PPL

All of the following commands assume to be the superuser. To become superuser, you have to enter the command:

sudo -s -H

after booting the BeagleBone Black and logging in into the debian account.

Otherwise you have to prefix every command with the word sudo. E.g. instead entering the command apt-get update enter the command sudo apt-get update.

Now, after you have become superuser, ist is a good advice to update the operation system with new packages by entrain the command

apt-get update

and

apt-get upgrade

This ensured the the operation system is up do date.

Looking carefully at the output of the apt-get upgrade command, you will recognize that an error occurs upgrading the dnsmasq package. This will result, that communication via the USB interface will not work correctly. To fix the error enter the following commands:

systemctl enable dnsmasq.service 
systemctl restart dnsmasq.service

If you have forgotten to enable the dnsmasq deamon, your host system will not obtain an IP address automatically after the next restart of the BeagleBone Black. In this case you have to assign an IP address manually.

The following additional packages are needed:

apt-get install cmake

at the time of writing this memo, the lastest kernel version of the Debian distribution was 4.4.68-ti-r112. To get the latest stable kernel release, that mostly is a newer kernel than the kernel of the Debian distribution, do the following:

cd /opt/scripts/tools/
git pull
./update_kernel.sh

Unfortunately, the is a bug in the kernel update script, resulting that the configuration file of dnsmasq server is wrong. To continue to use the USB interfaces for Internet access enter the following command:

touch /etc/dnsmasq.d/.SoftAp0

This touch command creates an empty file, indicating not to change the dnsmasq configuration file at the boot process. Now boot the BeagleBone Black once again.

reboot

After the reboot von in again. The cost of the command

uname -a
Linux beaglebone 4.4.155-ti-r155 #1 SMP Thu May 23 05:22:53 UTC 2019 armv7l GNU/Linux

Now the kernel version 4.4.155-ti-r155 is installed.

In PPL, we need an device tree overlay to enable the SPI controller and the PRU. Therefore a patched device tree compiler is needed. An addition the device tree overlay blobs for the peripheral is helpful.

To install these things go to directory:

cd /opt/source/bb.org-overlays

Now, test if the device tree compiler is installed:

dtc --version
Version: DTC 1.4.4

Update dtc by executing:

./dtc-overlay.sh

Install the device tree overlay blobs:

./install.sh

The pins of HDMI are multiplexed with the pins of the SPI. In order to use the SPI, the HDMI pins must be disabled by uncommenting the following line in the file /boot/uEnv.txt:

##BeagleBone Black: HDMI (Audio/Video) disabled:
dtb=am335x-boneblack-emmc-overlay.dtb

Per default the pins of the BeagleBone Black are wired for universal use, meaning the pins are connected to the common used devices. This will result in an error, if loading your own device tree overlay.

To disable universal use, change the following line in the file /boot/uEnv.txt

cmdline=coherent_pool=1M net.ifnames=0 quiet cape_universal=enable

to

cmdline=coherent_pool=1M net.ifnames=0 quiet

To make the changes effective, reboot.

To test, that the HDMI is disables execute the following command:

grep "pin 41"  /sys/kernel/debug/pinctrl/44e10800.pinmux/pins

and look, that the output matches the following:

pin 41 (44e108a4.0) 0000002f pinctrl-single

If the Hex-code is not 0000002f the HDMI is still enabled.

¹⁾

The communication between ARM host processor an the PRU (Programmable Realtime Unit) is implemented either by the Remoteproc-Driver or the UIO PRU Driver. Per default the Remoreproc-Driver is enabled. In this memo, it will be described, how to enable the UIO PRU Driver.

After booting an fresh Debian image an executing the command:

lsmod | grep uio
uio_pdrv_genirq         4243  0 
uio                    10972  1 uio_pdrv_genirq

and looking at the output, it seems, the UIO PRU Driver (uio_pdrv_genirq) is already been enabled. But this Assumption is wrong. It needs several steps to enable the driver:

Go to the directory:

cd /opt/source/dtb-4.4-ti/

Now, modify the file src/arm/am335x-boneblack-emmc-overlay.dts by uncommenting the UIO PRU part and commenting the the remoterpc part:

/* #include "am33xx-pruss-rproc.dtsi" */ /* line 22 */
#include "am33xx-pruss-uio.dtsi"         /* line 32 */

After editing is finished, compile the device tree files by

make

and install the device tree binary by

make install

In the last step, the binary device tree must be enables in the file /boot/uEnv.txt. If not already done look at Disable HDMI.

Finally the UIO PRU driver must be enables and the Remoteproc driver must be disables by editing the file /etc/modprobe.d/pruss-blacklist.conf.

Remove the line 'blacklist uio_pruss' and add the following lines:

blacklist pruss
blacklist pruss_intc
blacklist pru-rproc
blacklist spidev

Afterward reboot the Beaglebone Black.

reboot

To check, if the device tree file has been loaded correctly, execute

lsmod
Module                  Size  Used by
pvrsrvkm              445708  0 
uio_pruss               4387  0 
evdev                  14151  1 
uio_pdrv_genirq         4243  0 
uio                    10972  2 uio_pruss,uio_pdrv_genirq
usb_f_acm               8681  2 
u_serial               14137  3 usb_f_acm
usb_f_ecm              11448  2 
8021q                  24428  0 
garp                    7497  1 8021q
mrp                     9351  1 8021q
stp                     2622  1 garp
llc                     6287  2 stp,garp
usb_f_mass_storage     50793  2 
usb_f_rndis            26505  4 
u_ether                14733  2 usb_f_ecm,usb_f_rndis
libcomposite           54424  18 usb_f_acm,usb_f_ecm,usb_f_rndis,usb_f_mass_storage
tieqep                 10365  0

Now only uu drivers are loaded and no Remoreproc drivers.