diff --git a/docs/assets/raspberry3.jpg b/docs/assets/raspberry3.jpg
deleted file mode 100644
index ddf7a36a..00000000
Binary files a/docs/assets/raspberry3.jpg and /dev/null differ
diff --git a/docs/en/SUMMARY.md b/docs/en/SUMMARY.md
index ca1ea2b2..d8987e0d 100644
--- a/docs/en/SUMMARY.md
+++ b/docs/en/SUMMARY.md
@@ -20,33 +20,36 @@
* [Connection to the Pixracer](connection.md)
* [Using QGroundControl over Wi-Fi](gcs_bridge.md)
* [Remote shell](ssh.md)
- * [Editing files](editing.md)
+ * [Command line interface](cli.md)
* [Automated self-checks](selfcheck.md)
* [Viewing images from cameras](web_video_server.md)
* Programming
- * [ROS](ros.md)
- * [MAVROS](mavros.md)
+ * [Overview](programming.md)
* [Camera orientation](camera_frame.md)
- * [Coordinate systems (frames)](frames.md)
- * [Simple OFFBOARD](simple_offboard.md)
- * [Code snippets](snippets.md)
* Fiducial markers (ArUco)
* [Overview](aruco.md)
* [Marker detection](aruco_marker.md)
* [Map-based navigation](aruco_map.md)
* [Optical Flow](optical_flow.md)
- * [Computer vision basics](camera.md)
+ * [Simple OFFBOARD](simple_offboard.md)
+ * [Coordinate systems (frames)](frames.md)
+ * [Code snippets](snippets.md)
+ * [Interfacing with a laser rangefinder](laser.md)
* [LED strip](leds.md)
* [Working with GPIO](gpio.md)
* [Interfacing with a sonar](sonar.md)
+ * [Computer vision basics](camera.md)
* [Using rviz and rqt](rviz.md)
- * [Interfacing with a laser rangefinder](laser.md)
- * [Software autorun](autolaunch.md)
+ * [Software autorun](autolaunch.md)
+ * [ROS](ros.md)
+ * [MAVROS](mavros.md)
* Supplementary materials
+ * [COEX Pix](coex_pix.md)
* [Guide on autonomous flight](auto_setup.md)
* [Hostname](hostname.md)
* [PX4 Simulation](sitl.md)
* [PID Setup](calibratePID.md)
+ * [Model files for parts](models.md)
* [ROS Kinetic installation](ros-install.md)
* [Remote control app](rc.md)
* [Wi-Fi Configuration](network.md)
@@ -75,5 +78,6 @@
* [Android RC app](android.md)
* [3D-scanning drone](3dscan.md)
* [Human pose estimation drone control](human_pose_estimation_drone_control.md)
+ * [Copter Hack 2019](copterhack2019.md)
* [Copter Hack 2018](copterhack2018.md)
* [Copter Hack 2017](copterhack2017.md)
diff --git a/docs/en/auto_setup.md b/docs/en/auto_setup.md
index 5513ecd1..1182c7ce 100644
--- a/docs/en/auto_setup.md
+++ b/docs/en/auto_setup.md
@@ -25,7 +25,7 @@ This manual contains links to other articles in which each of the topics address
- You can change the name and password of the network if you want to. See the article "[Network Settings] (network.md # change-password-or-ssid-network-name)". The remaining operations with the network are unnecessary.
-- Use the nano editor to edit files. [Instructions for working with nano] (editing.md).
+- Use the nano editor to edit files. [Instructions for working with nano](cli.md#editing).
> **Hint** In nano, you can only move the cursor with the arrow keys on the keyboard.
diff --git a/docs/en/camera_frame.md b/docs/en/camera_frame.md
index 1305ab43..0a56ec07 100644
--- a/docs/en/camera_frame.md
+++ b/docs/en/camera_frame.md
@@ -2,7 +2,7 @@
> **Note** Documentation for the versions [of image](image.md), starting with **0.15**. For earlier versions, see [documentation for version **0.14**](https://github.com/CopterExpress/clever/blob/v0.14/docs/ru/camera_frame.md).
-Position and orientation of the main camera is determined in file `~/catkin_ws/src/clever/clever/launch/main_camera.launch`:
+Position and orientation of the main camera is [set in file](cli.md#editing) `~/catkin_ws/src/clever/clever/launch/main_camera.launch`:
```xml
diff --git a/docs/en/cli.md b/docs/en/cli.md
new file mode 100644
index 00000000..840b1c05
--- /dev/null
+++ b/docs/en/cli.md
@@ -0,0 +1,80 @@
+# Command line interface
+
+The Raspberry Pi OS, Raspbian, uses CLI as its primary user interface (which is common for Linux-based operating systems). You can use [a secure shell connection](ssh.md) to access the command line.
+
+## Basic commands
+
+> **Hint** Double-tapping the `Tab ↹` key autocompletes the command or its argument. This is known as "tab completion".
+
+Show the contents of the current directory:
+
+```bash
+ls
+```
+
+Change current (working) directory:
+
+```bash
+cd catkin_ws/src/clever/clever/launch
+```
+
+Go one directory level up:
+
+```bash
+cd ..
+```
+
+Print path to the current directory:
+
+```bash
+pwd
+```
+
+Print contents of the `file.py` file:
+
+```bash
+cat file.py
+```
+
+Run `file.py` as a Python script:
+
+```bash
+python file.py
+```
+
+Reboot Raspberry Pi:
+
+```bash
+sudo reboot
+```
+
+You can terminate currently running (foreground) program by pressing `Ctrl`+`C`.
+
+Read more about the Linux command line in the Raspberry Pi documentation: https://www.raspberrypi.org/documentation/linux/usage/commands.md.
+
+## Editing files {#editing}
+
+You can use **nano** to edit files on the Raspberry Pi. It is one of the more user-friendly console-based text editor.
+
+1. Use the following command to edit or create a file:
+
+ ```bash
+ nano path/to/file
+ ```
+
+ For example:
+
+ ```bash
+ nano ~/catkin_ws/src/clever/clever/launch/clever.launch
+ ```
+
+ 
+2. Edit the file.
+3. Press `Ctrl`+`X`, `Y`, `Enter` to save your file and exit.
+4. Restart the `clever` package if you've changed .launch files:
+
+ ```bash
+ sudo systemctl restart clever
+ ```
+
+You may also use other editors like **vim** if you prefer.
diff --git a/docs/en/coex_pix.md b/docs/en/coex_pix.md
new file mode 100644
index 00000000..78c33364
--- /dev/null
+++ b/docs/en/coex_pix.md
@@ -0,0 +1,60 @@
+# COEX Pix
+
+The **COEX Pix** flight controller is a modified [Pixracer](https://docs.px4.io/v1.9.0/en/flight_controller/pixracer.html) FCU. It is a part of the **Clever 4** quadrotor kit.
+
+## Revision 1.1
+
+### Physical specs
+
+* Board size: 35x35 mm.
+* Mounting hole pattern: standard 30.5 mm.
+* Mounting hole diameter: 3.2 mm.
+* Board mass: 9 g.
+* Operating temperature range: -5..+65 ºC.
+* Input voltage: 4.8..5.5 V.
+
+### Key features
+
+* Main System-on-Chip: *STM32F427VIT6*.
+* FRAM chip: *FM25V02A*
+* Built-in sensors:
+ * *MPU9250* 9DOF accelerometer/gyroscope/magnetometer.
+ * *MS5607* barometer.
+
+### Ports
+
+* *TELEM 1* (JST-GH 4 pin) – telemetry port 1, UART.
+* *TELEM 2* (JST-GH 4 pin) – telemetry port 2, UART.
+* *GPS* (JST-GH 6 pin) – GNSS (UART) and external compass (I2C) port.
+* *I2C* (JST-GH 4 pin) – I2C port for supported devices (shares lanes with *GPS* port).
+* *PWR* (JST-GH 6 pin) – port for PDB connection (COEX PDB or compatible), with two power lanes, two ground lanes, and voltage and current sensor inputs.
+* *RC IN* (JST-GH 4 pin) – RC input port with RSSI pin. Supports PPM and S.BUS protocols.
+* Micro USB port for PC connection (USB 2.0/1.1).
+* MicroSD slot (supports up to 32gb microSD cards).
+* 6 servo outputs for ESCs and other peripherals.
+
+### Port pinouts
+
+
+
+
+
+> **Note** On rev. 1.0 boards *RC IN* port and microSD slot are switched. Pinout for the *RC IN* port is the same on these boards.
+
+### Mounting suggestions
+
+**Important**: The board is meant to be installed with a non-standard orientation (roll 180º, yaw 90º) on the Clever airframe. Therefore, the `SENS_BOARD_ROT` PX4 parameter should be set to `ROLL 180, YAW 90`.
+
+### Usage notes
+
+In order to reduce magnetic interference from the PDB and power cables you should mount the FCU as far away from these parts as possible. You should have at least 15 mm clearance from high-power parts.
+
+You may want to disable internal compass if you're using an external GNSS+compass module.
+
+If your drone does not have a protective cover for the FCU, you should place a piece of foam over the barometer.
+
+The FCU has power passthrough from the *PWR* input to the servo rail. Supplying additional power to the servo rail is not recommended if the *PWR* input is used. Powering the FCU from USB and *PWR*/*AUX* inputs is acceptable.
+
+### Board specifics
+
+The board utilizes low-noise DC-DC converters, voltage inputs have LC and ferrite filters.
diff --git a/docs/en/connection.md b/docs/en/connection.md
index f174e4d9..0529ff23 100644
--- a/docs/en/connection.md
+++ b/docs/en/connection.md
@@ -1,60 +1,52 @@
-Connecting Pixhawk/Pixracer to Raspberry Pi
-===
+# Connecting Raspberry Pi to the flight controller
-To program [autonomous flights](simple_offboard.md) [work with Pixhawk (Pixracer) over Wi-Fi](gcs_bridge.md), use [of a phone transmitter] (rc.md), and other functions, it is necessary to connect Raspberry Pi to Pixhawk (Pixracer).
+In order to program [autonomous flights](simple_offboard.md), [work with Pixhawk or Pixracer over Wi-Fi](gcs_bridge.md), use [controller app](rc.md) and access other functions you need to connect your Raspberry Pi to the flight controller.
-Check operability of the connection [by running on Raspberry Pi](ssh.md):
+## USB connection
-```bash
-rostopic echo /mavros/state
-```
+USB connection is the preferred way to connect to the flight controller.
-The `connected` field should contain value `True`.
+1. Connect your FCU to the Raspberry Pi using a microUSB to USB cable.
+2. [Connect to the Raspberry Pi over SSH](ssh.md).
+3. Make sure the connection is working by [running the following command on the Raspberry Pi](ssh.md):
-Connection via USB
----
+ ```bash
+ rostopic echo /mavros/state
+ ```
-Connect Pixhawk/Pixracer to micro USB in Raspberry Pi with a USB cable.
+ The `connected` field should have the `True` value.s
-Make sure that in Clever launch file (`~/catkin_ws/src/clever/clever/launch/clever.launch`), connection type is set to USB:
+> **Hint** You need to set the `CBRK_USB_CHK` [parameter](px4_parameters.md) to 197848 for the USB connection to work.
-```xml
-
-```
+## UART connection
-After the launch file is edited, restart package `clever`:
+
-```bash
-sudo systemctl restart clever
-```
+UART connection is another way for the Raspberry Pi and FCU to communicate.
-> **Hint** For correct operation of the Raspberry Pi connection to Pixhawk via USB, set value of [parameter](px4_parameters.md) `CBRK_USB_CHK` to 197848.
+1. Connect Raspberry Pi to your FCU using a UART cable.
+2. [Connect to the Raspberry Pi over SSH](ssh.md).
+3. Change the connection type in `~/catkin_ws/src/clever/clever/launch/clever.launch` to UART:
-Connection via UART
----
+ ```xml
+
+ ```
-TODO connection diagram
+ Be sure to restart the `clever` service after editing the .launch file:
-Make sure that in Clever launch file (`~/catkin_ws/src/clever/clever/clever.launch`), connection type is set to UART:
+ ```bash
+ sudo systemctl restart clever
+ ```
-```xml
-
-```
+> **Hint** Set the `SYS_COMPANION` PX4 parameter to 921600 to enable UART on the FCU.
-After the launch-file is edited, restart package `clever`:
+## SITL connection
-```bash
-sudo systemctl restart clever
-```
-
-> **Hint** For correct operation of the Raspberry Pi connection to Pixhawk via UART, set value of parameter`SYS_COMPANION` to 921600.
-
-Connection to SITL
----
-
-To connect locally/remotely to a running [SITL](sitl.md), set argument `fcu_conn` to `udp`, and `fcu_ip` to the IP address of the machine where SITL is running (`127.0.0.1` for local):
+In order to connect to a local or a remote [SITL](sitl.md) instance set the `fcu_conn` parameter to `udp` and `fcu_ip` to the IP address of the SITL instance (`127.0.0.1` if you are running the instance locally):
```xml
```
+
+**Next**: [Using QGroundControl over Wi-Fi](gcs_bridge.md)
diff --git a/docs/en/copterhack2019.md b/docs/en/copterhack2019.md
new file mode 100644
index 00000000..dad0b273
--- /dev/null
+++ b/docs/en/copterhack2019.md
@@ -0,0 +1,94 @@
+# Copter Hack 2019
+
+The [Copter Hack 2019](https://copterexpress.timepad.ru/event/1017592/) hackathon took place on the 11th to 13th of October in the "Moscow" Technopolis.
+
+Event page: https://coex.tech/copterhack.
+
+Hackathon chat: https://t.me/CopterHack.
+
+Timepad event page: https://copterexpress.timepad.ru/event/1017592/.
+
+## Information for participants
+
+### COEX Pix specifics
+
+Be sure to set the *Autopilot orientation* parameter to `ROTATION_ROLL_180_YAW_90` if you're using the *COEX Pix* flight controller. This parameter should be applied during calibration of each sensor.
+
+
+
+This parameter is used for *IMU* orientation correction.
+
+### Suggested image versions
+
+Raspberry Pi versions 3B+ and lower: [v0.18](https://github.com/CopterExpress/clever/releases/tag/v0.18)
+
+Raspberry Pi version 4: [v0.19-alpha.1](https://github.com/CopterExpress/clever/releases/tag/v0.19-alpha.1)
+
+### Camera orientation
+
+Some drones have the camera mounted with the cable going forward. You should set this orientation in the `main_camera.launch` file in the `clever` package.
+
+Further reading: [Camera orientation](camera_frame.md)
+
+### Using Optical Flow
+
+In order to enable optical flow set `optical_flow` and `rangefinder_vl53l1x` parameters to `true` in `clever.launch`.
+
+Enable `pub agl as lpos down` in `LPE_FUSION` parameter using QGroundControl.
+
+Make sure the rangefinder is mounted correctly and is working (see [Interfacing with a laser rangefinder](laser.md)).
+
+Further reading: [Optical Flow](optical_flow.md).
+
+### Using ArUco map
+
+Use the `cmit.txt` map. See [instructions](aruco_map.md).
+
+### Drone batteries
+
+**The battery indicator should be connected to the battery at all times. The organizers will not replace your damaged batteries!**
+
+### Flight videos
+
+Be sure to record **ALL** your flights on video! If your drone fails before your presentation, you'll be able to at least show your videos.
+
+### Yaw problem
+
+The v1.8.2-clever.7 FCU firmware has a potential bug that manifests during VPE (marker-based) flights. If your drone does not correct its yaw when using ArUco markers, try using an older firmware version (v1.8.2-clever.6, available from https://github.com/CopterExpress/Firmware/releases/tag/v1.8.2-clever.6). Download `px4fmu-v4_default.px4` for COEX Pix.
+
+### `navigate` service problem
+
+The 0.18 Raspberry Pi image has a potential bug that makes the drone fly through waypoints too fast. Try setting the `nav_from_sp` parameter to `false` in `~/catkin_ws/src/clever/clever/launch/clever.launch` if you are affected by it:
+
+```xml
+
+
+
+
+
+
+
+
+```
+
+## Lectures (in Russian)
+
+Lecture 1: Introduction – https://www.youtube.com/watch?v=cjtmZNuq7z0.
+
+Lecture 2: FCU setup – https://www.youtube.com/watch?v=PJNDYFPZQms.
+
+Lecture 3: PX4 architecture – https://www.youtube.com/watch?v=_jl7FImq3jk.
+
+Lecture 4: Autonomous flights – https://www.youtube.com/watch?v=ThXiNG1IzvI.
+
+Be sure to check out other videos on the COEX YouTube channel: https://www.youtube.com/channel/UCeCu93sLBkcgbIkIC7Jaauw/featured.
+
+## Results
+
+Winners:
+
+1. Bulbolet – potato delivery using a smart hoist.
+2. Copter don't hurt me – controlling drone using a neural interface.
+3. import torch – active track using neural networks.
+4. Autobot – freeze light through a VK bot.
+5. Stardust Crusaders – AR drone simulation.
diff --git a/docs/en/editing.md b/docs/en/editing.md
deleted file mode 100644
index d0d2073d..00000000
--- a/docs/en/editing.md
+++ /dev/null
@@ -1,5 +0,0 @@
-# Editing files
-
-Use **nano** text editor to edit files on a Raspberry Pi.
-
-
diff --git a/docs/en/frames.md b/docs/en/frames.md
index 9d3bcffd..b44bddb3 100644
--- a/docs/en/frames.md
+++ b/docs/en/frames.md
@@ -12,6 +12,11 @@ Main frames in the `clever` package:
* `body` is bound to the drone, but its Z axis points up regardless of the drone's pitch and roll. It is shown by the red, blue and green lines in the illustration;
* `navigate_target` is bound to the current navigation target (as set by the [navigate](simple_offboard.md#navigate) service).
+Additional frames become available when [ArUco positioning system](aruco.md) is active:
+
+* `aruco_map` is bound to the currently active [ArUco map](aruco_map.md);
+* `aruco_N` is bound to the [marker](aruco_marker.md) with ID=N.
+
> **Hint** Frames that are bound to the drone are oriented according to [the ROS convention](http://www.ros.org/reps/rep-0103.html): the X axis points forward, Y to the left, and Z up.
3D visualization of the coordinate systems can be viewed using [rviz](rviz.md).
diff --git a/docs/en/gcs_bridge.md b/docs/en/gcs_bridge.md
index 5aecdbbd..9c5c7826 100644
--- a/docs/en/gcs_bridge.md
+++ b/docs/en/gcs_bridge.md
@@ -67,3 +67,5 @@ Change parameter `gcs_bridge` in the launch file:
```
After opening the QGroundControl application, the connection should be established automatically.
+
+**Next**: [Remote access using SSH](ssh.md)
diff --git a/docs/en/models.md b/docs/en/models.md
new file mode 100644
index 00000000..ffe6fed9
--- /dev/null
+++ b/docs/en/models.md
@@ -0,0 +1,15 @@
+# Model files for parts
+
+This page contains models and drawings of some of the drone parts. They can be used for 3D printing and/or laser cutting replacement parts.
+
+## Clever 4
+
+### Battery holder
+
+File: [`battery_holder.stl`](https://github.com/CopterExpress/clever/raw/master/docs/assets/battery_holder.stl).
+
+Filament: PLA/ABS/SBS.
+
+Infill: 50% or more.
+
+Description: the holder should be installed on the top deck. It allows the user to secure the battery with the battery strap and to mount your battery level indicator using a 3M pad.
diff --git a/docs/en/modes.md b/docs/en/modes.md
index 08dc7ee4..7fd6c45a 100644
--- a/docs/en/modes.md
+++ b/docs/en/modes.md
@@ -35,7 +35,7 @@ In manual mode the pilot controls the drone directly. GPS, computer vision data,
* **ALTCTL** (ALTITUDE) — control of the altitude rate, pitch, roll and yaw angular velocity. Requires a barometer or another altitude source.
* **POSCTL** (POSITION) — control of the altitude rate, forward/backward and right/left speed, and yaw angular velocity. It is the easiest flying mode. The barometer, GPS, computer vision, and other sensors are used.
-### Auto flight modes
+### Auto flight modes {#auto}
In autonomous flight modes the quadcopter ignores the control signals from the transmitter and uses a program to fly.
diff --git a/docs/en/programming.md b/docs/en/programming.md
new file mode 100644
index 00000000..6bdba0b6
--- /dev/null
+++ b/docs/en/programming.md
@@ -0,0 +1,96 @@
+# Programming
+
+
+
+The Clever platform allows a [Raspberry Pi](raspberry.md) computer to be used for programming autonomous flights. The flight program is typically written using the Python programming language. The program may [receive telemetry data](simple_offboard.md#get_telemetry) (which includes battery data, attitude, position, and other parameters) and send commands like: [fly to a point in space](simple_offboard.md#navigate), [set attitude](simple_offboard.md#set_attitude), [set angular rates](simple_offboard.md#set_rates), and others.
+
+The platform utilizes the [ROS framework](ros.md), which allows the user program to communicate with the Clever services that are running as a `clever` systemd daemon. The [MAVROS](mavros.md) package is used to interact with the flight controller.
+
+PX4 uses [OFFBOARD mode](modes.md#auto) for autonomous flights. The Clever API can be used to transition the drone to this flight mode automatically. If you need to interrupt the autonomous flight, use your flight mode stick on your RC controller to transition to any other flight mode.
+
+## Positioning system {#positioning}
+
+A drone has to use a positioning system to be able to hover still or to fly from point to point. The system should compute the drone position and feed this data into the flight controller. Clever allows using multiple positioning systems, such as [optical flow](optical_flow.md) (requires a [camera](camera.md) and a [rangefinder](laser.md)), [fiducial markers](aruco.md) (requires a camera and markers), GPS and others.
+
+### Optical flow
+
+Optical flow is used to compute shifts between consecutive frames and to use this data to compute the drone shifting in space.
+
+Read more in the [Optical Flow article](optical_flow.md).
+
+### ArUco markers
+
+Fiducial markers allow the drone to compute its position relative to these markers. This data may then be transferred to the flight controller.
+
+Read more about [ArUco markers](aruco.md) in our articles about them.
+
+### GPS (outdoor flight)
+
+GPS allows you to specify global Earth coordinates (latitude and longitude). The [`navigate_global`](simple_offboard.md#navigate_global) function takes these as parameters instead of the usual cartesian coordinates.
+
+Read more in the [GPS connection](gps.md) article.
+
+## Autonomous flight {#flight}
+
+After you've configured your positioning system, you can start writing programs for autonomous flights. Use the [SSH connection to the Raspberry Pi](ssh.md) to run your scripts. In order to run a Python script use the `python` command:
+
+```bash
+python flight.py
+```
+
+Below is a complete flight program that performs a takeoff, flies forward and lands:
+
+```python
+#coding: utf8
+
+import rospy
+from clever import srv
+from std_srvs.srv import Trigger
+
+rospy.init_node('flight')
+
+get_telemetry = rospy.ServiceProxy('get_telemetry', srv.GetTelemetry)
+navigate = rospy.ServiceProxy('navigate', srv.Navigate)
+land = rospy.ServiceProxy('land', Trigger)
+
+# Takeoff and hover 1 m above the ground
+navigate(x=0, y=0, z=1, frame_id='body', auto_arm=True)
+
+# Wait for 3 seconds
+rospy.sleep(3)
+
+# Fly forward 1 m
+navigate(x=1, y=0, z=0, frame_id='body')
+
+# Wait for 3 seconds
+rospy.sleep(3)
+
+# Perform landing
+land()
+```
+
+> **Note** The `navigate` function call is not blocking; that is, the program will continue executing the next commands before the drone arrives at the set point. Look at the [`navigate_wait`](snippets.md#block-nav) snippet for a blocking function.
+
+Note that only the first `navigate` call has its `auto_arm` parameter set to `True`. This parameter arms the drone and transitions it to the OFFBOARD flight mode.
+
+The `frame_id` parameter specifies which frame of reference will be used for the target point:
+
+* `body` is rigidly bound to the drone body;
+* `navigate_target` has its origin at the last target point for `navigate`;
+* `map` is the drone's local frame;
+* `aruco_map` is bound to the ArUco marker map;
+* `aruco_N` is bound to the marker with ID=N.
+
+Read more in the [coordinate systems](frames.md) article.
+
+You can also use the ["Autonomous flight"](simple_offboard.md) article as an API reference.
+
+## Additional periphery
+
+The Clever platform also exposes APIs for interacting with other peripherals. Read more in the following articles:
+
+* [LED strip](leds.md);
+* [laser rangefinder](laser.md);
+* [GPIO](gpio.md);
+* [ultrasonic rangefinder](sonar.md);
+* [camera](camera.md).
diff --git a/docs/en/raspberry.md b/docs/en/raspberry.md
index 47326ca1..a1be6ef8 100644
--- a/docs/en/raspberry.md
+++ b/docs/en/raspberry.md
@@ -3,7 +3,9 @@ Raspberry Pi
**Raspberry Pi** is a single-board computer that fits in the palm, created on the basis of ARM mobile microprocessor. It features low energy consumption, and it can even run on solar panels. Raspberry Pi 3 is included in the kits for programmable quadcopters "Clever".
-
+
+
+Technical specifications:
* Weight is 45 grams.
* Clock rate is 1.2 GHz.
@@ -12,19 +14,6 @@ Raspberry Pi
* Four USB 2.0 ports.
* An HDMI port.
-The scope of Raspberry Pi computer application is quite wide, since after all it is quite a full-fledged computer. If you need a machine to solve simple problems that do not require too many resources in terms of calculations, you can safely connect your Raspberry Pi device to the standard PC elements: a monitor, a mouse, or a keyboard.
+Raspberry Pi is connected to the flight controller in the Clever kit and is used as a companion computer. It can be used to [connect to the drone over Wi-Fi](wifi.md), perform autonomous flights, access peripherals and much more.
-The Raspberry Pi is a very popular platform where you can implement a variety of projects, such as:
-
-* a home automation server (or a "smart house" system);
-* a data storage server (NAS);
-* a home media server;
-* a "think-tank" for automated machines or robots.
-
-In fact, we will use it as the last in the list, due to its ability to connect to the Pixhawk autopilot.
-
-See more:
-
-* [RPi image](image.md)
-* [SSH access](ssh.md)
-* [Network setup](network.md)
+**Next**: [Raspberry Pi image](image.md)
diff --git a/docs/en/ssh.md b/docs/en/ssh.md
index c8ff99f3..dcbd8ba9 100644
--- a/docs/en/ssh.md
+++ b/docs/en/ssh.md
@@ -25,3 +25,5 @@ Web access
Starting with version 0.11.4 [of the image](image.md), access to the shell is also available via a web browser (using [Butterfly](https://github.com/paradoxxxzero/butterfly)). To gain access, open web page http://192.168.11.1, and select link *Open web terminal*:
+
+**Next**: [Command-line interface](cli.md)
diff --git a/docs/en/wifi.md b/docs/en/wifi.md
index 50a532e4..412d1233 100644
--- a/docs/en/wifi.md
+++ b/docs/en/wifi.md
@@ -15,4 +15,4 @@ After connecting to Clever Wi-Fi, open http://192.168.11.1 in you web browser. I
-**Next**: [Using QGroundControl via Wi-Fi](gcs_bridge.md).
+**Next**: [Connecting Raspberry Pi to the flight controller](connection.md).