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Dependencies

Ubuntu 2015.04 was used to build Debian/Ubuntu SD card images for Red Pitaya.

The next two packages need to be installed:

sudo apt-get install debootstrap qemu-user-static

Image build Procedure

Multiple steps are needed to prepare a proper SD card image.

  1. Bootstrap Debian system with network configuration and Red Pitaya specifics.
  2. Add Red Pitaya ecosystem ZIP.
  3. Optionally install Wyliodrin.

Debian bootstrap

Run the next command inside the project root directory. Root or sudo privileges are needed.

sudo OS/debian/image.sh

This will create an image with a name containing the current date and time. Two scripts debian.sh and redpitaya.sh will also be called from image.sh.

debian.sh bootstraps a Debian system into the EXT4 partition. It also updates packages and adds a working network configuration for Red Pitaya. redpitaya.sh extracts ecosystem*.zip (if one exists in the current directory) into the FAT partition. It also configures some Red Pitaya Systemd services.

The generated image can be written to a SD card using the dd command or the Disks tool (Restore Disk Image).

dd bs=4M if=debian_armhf_*.img of=/dev/sd?

NOTE: To get the correct destination storage device, read the output of dmesg after you insert the SD card. If the wrong device is specified, the content of another drive may be overwritten, causing permanent loose of user data.

Red Pitaya ecosystem extraction

In case ecosystem*.zip was not available for the previous step, it can be extracted later to the FAT partition (128MB) of the SD card. In addition to Red Pitaya tools, this ecosystem ZIP file contains a boot image, boot scripts, the Linux kernel and a Buildroot filesystem. Two boot scripts are provided:

  • u-boot.scr.buildroot (default) for booting into the Buildroot system, here the Debian EXT4 partition is not needed
  • u-boot.scr.debian for booting into the Debian system To enable booting into Debian just change the default boot script:
cp u-boot.scr.debian u-boot.scr

If there are no changes needed to the Debian system, but a new ecosystem is available, then there is no need to bootstrap Debian. Instead it is enough to delete all files from the FAT partition and repeat the ZIP file extraction and boot scrip renaming.

Wyliodrin

Unfortunately there are issues with Wyliodrin install process inside a virtualized environment. Therefore the provided script wiliodrin.sh must be run from a shell on a running Red Pitaya board. The script can be copied to the FAT partition and executed from the /root/ directory. Some code which is meant to be executed on the development machine, should be comment out (everything outside the chroot, including the chroot lines themselves).

cd /root
. /opt/redpitaya/wyliodrin.sh

The Wyliodrin team provided the initial support for Red Pitaya inside the libwyliodrin library. We are using a fork of the library which includes a few bug fixes and new features. Please have a look at the commit history for details. It would make sense to ask the Wyliodrin team to accept this changes into upstream.

https://github.com/RedPitaya/libwyliodrin

Some effort was made to port the newer C based wyliodrin-server instead of using the current node.js based server. Most of the effort was spent on attempts to replace compiling dependencies from source with packages provided in Debian. The unfinished branch can be provided to interested developers.

Reducing image size

A cleanup can be performed to reduce the image size. Various things can be done to reduce the image size:

  • remove unused software (this could be software which was needed to compile applications)
  • remove unused source files (remove source repositories used to compile applications)
  • remove temporary files
  • zero out empty space on the partition

The next code only removes APT temporary files and zeroes out the filesystem empty space.

apt-get clean
cat /dev/zero > zero.file
sync
rm zero.file
history -c

Creating a SD card image

Since Wiliodrin and maybe the ecosystem ZIP are not part of the original SD card image. The updated SD card contents should be copied into an image using dd or the Disks tool (Create Disk Image).

dd bs=4M if=/dev/sd? of=debian_armhf_*_wyliodrin.img

Initially the SD card image was designed to be about 3.7GB in size, so it would fit all 4GB SD cards. If the image is created from a larger card, it will contain empty space at the end. To remove the empty space from the SD card image do:

head -c 3670016000 debian_armhf_*_wyliodrin.img > debian_armhf_*_wyliodrin-short.img
mv debian_armhf_*_wyliodrin-short.img debian_armhf_*_wyliodrin.im

The image size can be further reduced by compressing it. Zip is used, since it is also available by default on MS Windows.

zip debian_armhf_*_wyliodrin.img > debian_armhf_*_wyliodrin.img.zip

Debian Usage

Systemd

Systemd is used as the init system and services are used to start/stop Red Pitaya applications/servers. Service files are located in OS/debian/overlay/etc/systemd/system/*.service.

service description
redpitaya_wyliodrin Wyliodrin server, is running by default
redpitaya_scpi SCPI server, is disabled by default, since it conflicts with WEB applications
redpitaya_discovery Device discovery, is run once after boot to send Ethernet MAC and IP address to a discovery server
redpitaya_nginx Nginx based server, serving WEB based applications

To start/stop a service, do one of the following:

systemctl start service_name
systemctl stop service_name

To enable/disable a service, so to determine if it will start at powerup, do one of the following:

systemctl enable service_name
systemctl disable service_name

To see the status of a specific service run:

systemctl