Debian Preparation for PPL

All of the following commands assume to be executed by 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, whose default password is temppwd.

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, it is a good advice to update the operating system with new packages by entering the command:

apt-get update

and

apt-get upgrade

This ensures the the operation system is up do date.

The following additional packages are needed:

apt-get install cmake

At the time of writing this memo, the kernel version included in the Debian image was 4.19.94-ti-r42. To update to the latest stable kernel release, that most likely is a newer kernel than the kernel of the Debian image, do the following:

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

Now boot the BeagleBone Black once again.

reboot

After the reboot let's check our new upgraded kernel:

uname -a
Linux beaglebone 4.19.94-ti-r72 #1buster SMP PREEMPT Tue Mar 8 22:13:06 UTC 2022 armv7l GNU/Linux

Now the kernel version 4.19.94-ti-r72 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. In addition the device tree overlay blobs for the peripherals are helpful.

The device tree overlay reflects the wiring of the BeagleBone Black with the CC1200. In first versions the wireing was made by hand. Today an adapter card is used. The wiring is is shown in Fig. 1 and described here.

Fig. 1: Wireing of BeagleBone Black with CC1200

To install these things go to directory and update the scripts first:

cd /opt/source/bb.org-overlays
git pull

Now, test if the device tree compiler is installed:

dtc --version
Version: DTC 1.4.7

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

disable_uboot_overlay_video=1

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

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

enable_uboot_cape_universal=1

To make the changes effective, reboot.

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

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

and look, that the output matches the following:

pin 41 (PIN41) 44e108a4 0000002f pinctrl-single

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

¹⁾

The communication between the ARM host processor and 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 a fresh Debian image and executing the command:

lsmod
 
Module                  Size  Used by
usb_f_acm              16384  2
u_serial               20480  3 usb_f_acm
usb_f_ecm              20480  2
usb_f_mass_storage     53248  2
usb_f_rndis            32768  4
u_ether                20480  2 usb_f_ecm,usb_f_rndis
libcomposite           65536  18 usb_f_ecm,usb_f_acm,usb_f_mass_storage,usb_f_rndis
pm33xx                 16384  0
wkup_m3_ipc            16384  1 pm33xx
wkup_m3_rproc          16384  1
uio_pdrv_genirq        16384  0
uio                    20480  1 uio_pdrv_genirq
pruss_soc_bus          16384  0
pru_rproc              28672  0
pruss                  16384  1 pru_rproc
irq_pruss_intc         20480  1 pru_rproc
remoteproc             57344  3 pru_rproc,wkup_m3_rproc,wkup_m3_ipc
virtio                 16384  1 remoteproc
virtio_ring            28672  1 remoteproc
spidev                 20480  0

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

We need to instruct the bootloader to load a device tree overlay blob which enables the UIO driver. This can be done by uncommenting the the following line in the file /boot/uEnv.txt:

uboot_overlay_pru=/lib/firmware/AM335X-PRU-UIO-00A0.dtbo

We should also disable the device tree overlay for the unused rproc driver by commenting out the following line in the same file:

uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-19-TI-00A0.dtbo

Finally the Remoteproc driver must be disabled by editing the file /etc/modprobe.d/pruss-blacklist.conf (create the file if it's not there).

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
pm33xx                 16384  0
wkup_m3_ipc            16384  1 pm33xx
wkup_m3_rproc          16384  1
remoteproc             57344  2 wkup_m3_rproc,wkup_m3_ipc
virtio                 16384  1 remoteproc
virtio_ring            28672  1 remoteproc
pvrsrvkm              421888  0
uio_pruss              16384  0
usb_f_acm              16384  2
u_serial               20480  3 usb_f_acm
uio_pdrv_genirq        16384  0
usb_f_ncm              28672  2
uio                    20480  2 uio_pruss,uio_pdrv_genirq
usb_f_mass_storage     53248  2
usb_f_rndis            32768  4
u_ether                20480  2 usb_f_ncm,usb_f_rndis
libcomposite           65536  18 usb_f_acm,usb_f_ncm,usb_f_mass_storage,usb_f_rndis

Now only UIO PRU drivers are loaded and no rproc drivers.