eive-obsw/README.md

# <a id="top"></a> <a name="linux"></a> EIVE On-Board Software

## Linux
These steps were tested for Ubuntu 20.04.
If not done yet, install the full C++ build chain:
```sh
sudo apt-get install build-essential
```

Linux has a limit to message queue message. Please see the section 
to set up UNIX environment for more information.
Sometimes, special steps are necessary so the real-time functionalities can be used
without root privileges. Instructions are contained in the setup section
for UNIX as well.

### Building the software

1. Clone the repository with
```sh
git clone https://egit.irs.uni-stuttgart.de/fsfw/fsfw_example.git
```

2. Update all the submodules
```sh
git submodule init
git submodule sync
git submodule update
```

3. After that, the linux binary can be built with:
```sh
make -j all
```
to compile for Linux. All will build the debug version,
which can also be built with the target `debug`. The optimized
release version can be built with the target `release`.

4. Run the binary located inside the `_bin` folder.

### Setting up UNIX environment for real-time functionalities
Please note that on most UNIX environments (e.g. Ubuntu), the real time functionalities 
used by the UNIX pthread module are restricted, which will lead to permission errors when creating these tasks
and configuring real-time properites like scheduling priorities.

To solve this issues, try following steps:

1. Edit the /etc/security/limits.conf 
file and add following lines at the end:
```sh
<username>   hard   rtprio  99
<username>   soft   rtprio  99
```
The soft limit can also be set in the console with `ulimit -Sr` if the hard
limit has been increased, but it is recommended to add it to the file as well for convenience.
If adding the second line is not desired for security reasons,
the soft limit needs to be set for each session. If using an IDE like eclipse 
in that case, the IDE needs to be started from the console after setting
the soft limit higher there. After adding the two lines to the file,
the computer needs to be restarted.

It is also recommended to perform the following change so that the unlockRealtime
script does not need to be run anymore each time. The following steps
raise the maximum allowed message queue length to a higher number permanently, which is 
required for some framework components. The recommended values for the new message
length is 130.

2. Edit the /etc/sysctl.conf file
```sh
sudo nano /etc/sysctl.conf
```
Append at end: 
```sh
fs/mqueue/msg_max = <newMsgMaxLen>
```
Apply changes with: 
```sh
sudo sysctl -p
```

A possible solution which only persists for the current session is
```sh
echo <newMsgMax> | sudo tee /proc/sys/fs/mqueue/msg_max
```
or running the `unlockRealtime` script.

3. Run the shell script inside the linux folder
```sh
./unlockRealtime
```
This script executes the `sudo setcap 'cap_sys_nice=eip' \<application\>`
command on the binaries, increases the soft real time limit of the current
session and increases the maximum number of message queues by setting
`/proc/sys/fs/mqueue/msg_max`.
All changes are only applied for the current session (read 2. and 3. for 
a permanent solution). If running the script before executing the binary does
not help or an warning is issue that the soft real time value is invalid, 
the hard real-time limit of the system might not be high enough (see step 1).

### Flight Software Framework (FSFW)

An EIVE fork of the FSFW is submodules into this repository.
To add the master upstream branch and merge changes and updates from it 
into the fork, run the following command in the fsfw folder first:

```sh
git remote add upstream https://egit.irs.uni-stuttgart.de/fsfw/fsfw.git
git remote update --prune
```

After that, an update can be merged by running

```sh 
git merge upstream/master
```

Alternatively, changes from other upstreams (forks) and branches can be merged like that in
the same way.