# Linux on DE0 Nano SoC

## Building Linux for DE0 Nano SoC

Download Buildroot and make a default configuration for DE0 Nano SoC.

```
cd ~
git clone git://git.buildroot.net/buildroot buildroot
cd buildroot
make ARCH=arm terasic_de10nano_cyclone5_defconfig
```

Then build an OS for the board.

```
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-
```

Write a prepared OS image into a microSD. sdX is a device name of the microSD in a desktop computer.

```
sudo dd if=~/buildroot/output/images/sdcard.img of=/dev/sdX bs=1M
```

If you don't know the name of the microSD card, you can use **fdisk**.

```
sudo fdisk -l
```

You can also use **sudo dmesg** it shows last connected device and it's letter.

Put microSD into a microSD slot. Power on the board and connect to a terminal using **picocom**.

```
picocom /dev/ttyUSB0 -b 115200
```

Login as **root**.

## Writing a software

Create a new directory for your first software project, name it lab6.

Inside the directory create file named **main.c** and copy and paste code from below to the file.

```
#include <stdio.h>


int main(int argc, char **argv) {

	printf("Hello World!\r\n");

	return( 0 );
}

```

Create **Makefile** for the project inside the directory.
```
#
TARGET = my_first_hps

#
CROSS_COMPILE = arm-linux-gnueabihf-
CFLAGS = -g -Wall  -I ${SOCEDS_DEST_ROOT}/ip/altera/hps/altera_hps/hwlib/include
LDFLAGS =  -g -Wall 
CC = $(CROSS_COMPILE)gcc
ARCH= arm

build: $(TARGET)

$(TARGET): main.o 
	$(CC) $(LDFLAGS)   $^ -o $@ 

%.o : %.c
	$(CC) $(CFLAGS) -c $< -o $@

.PHONY: clean
clean:
	rm -f $(TARGET) *.a *.o *~
```

Open terminal in the directory and build your first project.

```
make
```
You should find a file named **my_first_hps** in the project directory.

## Copying file to the prototyping board

### Directly

Copy **my_first_hps** into microSD card to **/home/root** directory.
Then safety remove the card from a computer and put it into the board.

### Over network

If the prototyping board is connected in a computer network, the files can be send to the board for example over ssh protocol using **scp** command.

#### Configuring Buildroot

To use **SSH** on the board, the Buildroot has to be rebuild.

Go into the Buildroot directory and run a configuration.

```
make ARCH=arm menuconfig
```


Press **/** to run finding in menu, then write **openssh**.

![Menuconfig screen](menuconfig.png)

![Menuconfig screen](findssh.png)

Next press **1 key** on the keyboard.

![Menuconfig screen](fresults.png)

Select **openssh** by pressing **space key** on the choice.

![Menuconfig screen](choice.png)

![Menuconfig screen](marked.png)

Press **Exit** in menu at bottom and save the new configuration.

![Menuconfig screen](save.png)

#### Rebuilding

Build Buildroot again.

```
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-
```

Write the new sdimage to the microSD card.

#### Configuring system

SSH works properly but we want to send files without asking about a user's password.

After login edit the sshd_config.

```
vi /etc/ssh/sshd_config 
```

Find and change below settings.

```
PermitRootLogin yes  
PasswordAuthentication yes                                          
PermitEmptyPasswords yes  
```

Write new settings and reboot the board.

```
reboot
```

### Sending files

Now you can send files directly to the board.

First check the board IP.

```
ifconfig eth0
```
<!---
```
ifconfig eth0 192.168.1.114
```
```
sopc-create-header-files ../terasic_led/led.sopcinfo --single hps_0.h --module hps_0
```
-->

Send **my_first_hps** using the scp, remember to change the IP address.

```
scp my_first_hps root@192.168.1.114:/root
```