* interface between the robot base camera and the rPi via USB, up to 15 FPS
Every LED is independent from each other, so it's possible to turn on the LEDs with different colors in the RGB color space (additive color mixing), as shown in the following figures.<br/>
* charging contact points in front for automatic charging. External docking station available
* several extension options. 6 i2C channels, 2 ADC inputs
* several LED to show the status of the rPi and the power/chargers
==I2C bus==
The infrareds are thought as identification sensors, this means that the robots can be recognized by an external device such as a camera observing their combination of infrareds turned on and off; for instance using 8 IRs it's possible to identify 256 different robots.
I2C is used to let communicate various elements present in the robot, Pi-puck and extensions. An overall schema is shown in the following figure:<br/>
An I2C switcher is included in the Pi-puck extension in order to support additional I2C buses (the RPi alone has only one usable I2C bus). These are needed to avoid conflicts between Time-of-Flight sensors that have a fixed I2C address.
=Getting started=
The communication between the e-puck and the module is via the I2C bus. Color commands are sent from the robot to the RGB panel (nothing is sent in the opposite way); this let us, for example, program the robot with a pre-fixed sequence of commands to send to the panel, resulting in a color animation. Other more elaborate demos could be implemented, reacting for example to the environment and nearby robots.<br/>
This introductory section explains the minimal procedures needed to work with the Raspberry Pi Zero W mounted on the Pi-puck extension board and gives a general overview of the available basic demos and scripts shipped with the system flashed on the micro SD. More advanced demos are described in the following separate sections (e.g. ROS), but the steps documented here are fundamental, so be sure to fully understand them. <br/>
Another possibility is to develop a demo running on a computer and connecting the computer to the e-puck through Bluetooth (the e-puck and the module are connected through I2C as before); in practice the robot receives commands from the PC and forwards them to the RGB panel. This forwarding is implemented in the e-puck firmware, presented afterwards.
The extension is mostly an interface between the e-puck robot and the Raspberry Pi, so you can exploit the computational power of a Linux machine to extend the robot capabilities.<br/>
=Electrical schema=
The circuit diagram of the rgb panel e-puck extension is available to the community on the following link [https://projects.gctronic.com/rgb-panel/rgb-ext-electrical-schema.pdf electrical schema].
In most cases, the Pi-puck extension will be attached to the robot, but it's interesting to note that it can be used also alone when the interaction with the robot isn't required.<br/>
=Software=
The following sections assume the full configuration (robot + extension), unless otherwise stated.
==E-puck firmware==
In order to play with the RGB extension for the e-puck robot you need to load the official e-puck firmware and set the selector on position 3 (advanced sercom protocol), refer to section [http://www.gctronic.com/doc/index.php/E-Puck#Standard_firmware E-Puck Standard firmware]. Basically the firmware contains a command to setup the color of each led and the state of each infrared sensor; in particular there are two commands (binary mode): 'W' and 'w'; the first one is used to set a single led or infrared sensor, the second is used to set all actuators at once.
==Requirements==
==RGB panel firmware==
The robot must be programmed with a special firmware in order to communicate via I2C bus with the Raspberry Pi mounted on the Pi-puck extension. The same I2C bus is shared by all the devices (camera, IMU, distance sensor, others extensions), the main microcontroller and the Raspberry Pi. Since the Raspberry Pi acts as I2C master, these devices will not be anymore reachable directly from the robot main microcontroller that will act instead as I2C slave.
Also the module requires a firmware running on it in order to handle the I2C communication and interpret the commands needed to turn on and off the sensors and color leds. The firmware can be downloaded from the following links ([https://projects.gctronic.com/rgb-panel/panel-firmware.zip panel-MPLAB], [https://projects.gctronic.com/rgb-panel/panel-firmware.hex panel-hex]).
===e-puck1===
==Demo - PC side==
The e-puck1 robot must be programmed with the following firmware [https://raw.githubusercontent.com/yorkrobotlab/pi-puck/master/e-puck1/pi-puck-e-puck1.hex pi-puck-e-puck1.hex].
A basic demo running on a computer was developed to control manually all the LEDs color and IRs state through a Bluetooth connection. The application is implemented with [https://www.qt.io/download Qt]. A snapshot of this demo is shown hereafter:<br/>
[http://www.gctronic.com/doc/images/LEDsTurret1.7.zip Download RGB Panel Basic Demo (Multiplatform)], built with Qt-5.10.1.
The e-puck2 robot must be programmed with the following firmware [https://projects.gctronic.com/epuck2/gumstix/e-puck2_main-processor_extension_b346841_07.06.19.elf e-puck2_main-processor_extension.elf (07.06.19)] and the selector must be placed in position 10.<br/>
The source code is available in the <code>gumstix</code> branch of the repo <code>https://github.com/e-puck2/e-puck2_main-processor</code>.
==Turn on/off the extension==
==e-puck2==
To turn on the extension you need to press the <code>auxON</code> button as shown in the follwoing figure; this will turn on also the robot (if not already turned on). Similarly, if you turn on the robot then also the extension will turn on automatically.<br/>
To play with the e-puck2 robot and RGB extension you can run the same [https://www.gctronic.com/doc/index.php?title=RGB_Panel#Demo_-_PC_side PC side application] that is used with the e-puck1. In this case the e-puck2 robot must be programmed with the [https://www.gctronic.com/doc/index.php?title=e-puck2#Factory_firmware factory firmware] and the selector must be placed in position 3.
To turn off the Pi-puck you need to press and hold the <code>auxON</code> button for 2 seconds; this will initiate the power down procedure.<br>
Beware that in order to change the selector postion, <b>both the e-puck2 and RGB panel must have the selector in the same position</b>, this means that if you want the position 3 selected, then both the selector of the robot and the selector of the RGB panel must be placed in position 3.
Beware that by turning off the robot, the extension will not be turned off automatically if it is powered from another source like the micro usb cable or a secondary battery. You need to use its power off button to switch it off. Instead if there is no other power source, then by turning off the robot also the extension will be turned off (not cleanly).
If you want to control the RGB extension directly from the e-puck2, then you can do it by using the I2C bus (see chapter [https://www.gctronic.com/doc/index.php?title=RGB_Panel#Registers Registers]). An example is provided to help you getting started, have a look at the following repository [https://github.com/e-puck2/e-puck2_rgb_panel https://github.com/e-puck2/e-puck2_rgb_panel].
==Console mode==
=Programming=
The Pi-puck extension board comes with a pre-configured system ready to run without any additional configuration.<br/>
==Registers==
In order to access the system from a PC in console mode, the following steps must be performed:<br/>
The LEDs and IRs are controlled by writing appropriate registers; the value within the registers represents the duty cycle that a LED/IR will reach, that is its brightness. The following table shows the registers used to configure the various LEDs and IRs.
1. connect a micro USB cable from the PC to the extension module. If needed, the drivers are available in the following link [https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers USB to UART bridge drivers]<br/>
2. execute a terminal program and configure the connection with 115200-8N1 (no flow control). The serial device is the one created when the extension is connected to the computer<br/>
!X !! RedX !! BlueX !! GreenX !! IRX
3. switch on the robot (the extension will turn on automatically); now the terminal should display the Raspberry Pi booting information. If the robot isn't present, then you can directly power on the extension board with the related button<br/>
4. login with <code>user = pi</code>, <code>password = raspberry</code><br/>
|-
|0 || 0x00 || 0x08 || 0x10 || 0xA4
==Battery charge==
|-
You can either charge the robot battery or the additional battery connected to the Pi-puck extension or both the batteries by simply plugging the micro USB cable.<br/>
|1 || 0x01 || 0x09 || 0x11 || 0xA5
The following figure shows the connector for the additional battery.<br/>
The robot can also autonomously charge itself if the charging wall is available. The Pi-puck extension includes two spring contacts on the front side that let the robot easily make contact with the charging wall and charge itself. The charging wall and the spring contacts are shown in the following figures:<br/>
A button is available to reset the robot, when pressed it will resets only the robot restarting its firmware. This is useful for instance during development or for specific demos in which a restart of the robot is needed. In these cases you don't need to turn off completely the robot (and consequently also the Pi-puck if energy is supplied by the robot) but instead you can simply reset the robot. The position of the reset button is shown in the following figure:<br/>
=How to communicate with the robot and its sensors=
|7 || 0x07 || 0x0F || 0x17 || 0xAB
==Communicate with the e-puck1==
|-
Refer to the repo [https://github.com/yorkrobotlab/pi-puck-e-puck1 https://github.com/yorkrobotlab/pi-puck-e-puck1].
|8 || 0x92 || 0x93 || 0x94 || -
==Communicate with the e-puck2==
An example showing how to exchange data between the robot and the Pi-puck extension is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/e-puck2/</code>.<br/>
You can build the program with the command <code>gcc e-puck2_test.c -o e-puck2_test</code>.<br/>
Now you can run the program by issueing <code>./e-puck2_test</code>; this demo will print the sensors data on the terminal and send some commands to the robot at 2 Hz.<br/>
The same example is also available in Python, you can run it by issueing <code>python3 e-puck2_test.py</code>.
===Packet format===
Extension to robot packet format, 20 bytes payload (the number in the parenthesis represents the bytes for each field):
{| border="1"
| Left speed (2)
| Right speed (2)
| Speaker (1)
| LED1, LED3, LED5, LED7 (1)
| LED2 RGB (3)
| LED4 RGB (3)
| LED6 RGB (3)
| LED8 RGB (3)
| Settings (1)
| Checksum (1)
|}
* Left, right speed: [-2000 ... 2000]
* Speaker: sound id = [0, 1, 2]
* LEDs on/off flag: bit0 for LED1, bit1 for LED3, bit2 for LED5, bit3 for LED7
* Checksum: Longitudinal Redundancy Check (XOR of the bytes 0..18)
Robot to extension packet format, 47 bytes payload (the number in the parenthesis represents the bytes for each field):
{| border="1"
| 8 x Prox (16)
| 8 x Ambient (16)
| 4 x Mic (8)
| Selector + button (1)
| Left steps (2)
| Right steps (2)
| TV remote (1)
| Checksum
|}
|}
* Selector + button: selector values represented by 4 least significant bits (bit0, bit1, bit2, bit3); button state is in bit4 (1=pressed, 0=not pressed)
</blockquote>
* Checksum: Longitudinal Redundancy Check (XOR of the bytes 0..45)
==Communicate with the IMU==
===e-puck1===
An example written in C showing how to read data from the IMU (LSM330) mounted on e-puck 1.3 is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/e-puck1/</code>.<br/>
You can build the program with the command <code>gcc e-puck1_imu.c -o e-puck1_imu</code>.<br/>
Now you can run the program by issueing <code>./e-puck1_imu</code> and then choose whether to get data from the accelerometer or gyroscope; this demo will print the sensors data on the terminal.<br/>
===e-puck2===
An example showing how to read data from the IMU (MPU-9250) is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/e-puck2/</code>.<br/>
You can build the program with the command <code>gcc e-puck2_imu.c -o e-puck2_imu</code>.<br/>
Now you can run the program by issueing <code>./e-puck2_imu</code> and then choose whether to get data from the accelerometer or gyroscope; this demo will print the sensors data on the terminal.<br/>
The same example is also available in Python, you can run it by issueing <code>python3 e-puck2_imu.py</code>.
==Communicate with the ToF sensor==
The Time of Flight sensor is available only on the e-puck2 robot.<br/>
First of all you need to verify that the VL53L0X Python package is installed with the following command: <code>python3 -c "import VL53L0X"</code>. If the command returns nothing you're ready to go, otherwise if you receive an <code>ImportError</code> then you need to install the package with the command: <code>pip3 install git+https://github.com/gctronic/VL53L0X_rasp_python</code>.<br/>
A Python example showing how to read data from the ToF sensor is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/e-puck2/</code>.<br/>
You can run the example by issueing <code>python3 VL53L0X_example.py</code> (this is the example that you can find in the repository [https://github.com/gctronic/VL53L0X_rasp_python/tree/master/python https://github.com/gctronic/VL53L0X_rasp_python/tree/master/python]).
==Capture an image==
The robot camera is connected to the Pi-puck extension as a USB camera, so you can access it very easily.<br/>
An example showing how to capture an image from the robot's camera using OpenCV is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/snapshot/</code>.<br/>
You can build the program with the command <code>g++ $(pkg-config --libs --cflags opencv) -ljpeg -o snapshot snapshot.cpp</code>.<br/>
Now you can run the program by issueing <code>./snapshot</code>; this will save a VGA image (JPEG) named <code>image01.jpg</code> to disk.<br/>
The program can accept the following parameters:<br/>
<code>-d DEVICE_ID</code> to specify the input video device from which to capture an image, by default is <code>0</code> (<code>/dev/video0</code>). This is useful when working also with the [http://www.gctronic.com/doc/index.php?title=Omnivision_Module_V3 Omnivision V3] extension that crates another video device; in this case you need to specify <code>-d 1</code> to capture from the robot camera.<br/>
<code>-n NUM</code> to specify how many images to capture (1-99), by default is 1<br/>
<code>-v</code> to enable verbose mode (print some debug information)<br/>
Beware that in this demo the acquisition rate is fixed to 5 Hz, but the camera supports up to '''15 FPS'''.<br/>
The same example is also available in Python, you can run it by issueing <code>python snapshot.py</code>.
==Communicate with the ground sensors extension==
Both e-puck1 and e-puck2 support the [https://www.gctronic.com/doc/index.php?title=Others_Extensions#Ground_sensors ground sensors extension].<br/>
This extension is attached to the I2C bus and can be read directly from the Pi-puck.<br/>
An example written in C showing how to read data from the ground sensors extension is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/ground-sensor/</code>.<br/>
You can build the program with the command <code>gcc groundsensor.c -o groundsensor</code>.<br/>
Now you can run the program by issueing <code>./groundsensor</code>; this demo will print the sensors data on the terminal.<br/>
The same example is also available in Python, you can run it by issueing <code>python3 groundsensor.py</code>.
==Communicate with the range and bearing extension==
Both e-puck1 and e-puck2 support the [https://www.gctronic.com/doc/index.php?title=Others_Extensions#Range_and_bearing range and bearing extension].<br/>
This extension is attached to the I2C bus and can be read directly from the Pi-puck.<br/>
An example written in C showing how to start playing with the range and bearing extension is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/randb/</code>. You need two boards: one is the transmitter (run <code>randb_tx</code>) and the other is the receiver (run <code>randb_rx</code>). The receiver will print the data received from the transmitter.<br/>
You can build the programs with the command <code>gcc randb_tx.c -o randb_tx</code> and <code>gcc randb_rx.c -o randb_rx</code>.<br/>
The same example is also available in Python, you can run it by issueing <code>python3 randb_tx.py</code> and <code>python3 randb_rx.py</code>.
==Wireless remote control==
If you want to control the robot from a computer, for instance when you have an algorithm that requires heavy processing not suitable for the Pi-puck or when the computer acts as a master controlling a fleet of robots that return some information to the controller, then you have 3 options:<br/>
1) The computer establishes a WiFi connection with the Pi-puck to receive data processed by the Pi-puck (e.g. results of an image processing task); at the same time the computer establishes a Bluetooth connection directly with the e-puck2 robot to control it.
:''Disadvantages'':
:- the Bluetooth standard only allow up to seven simultaneous connections
:- doubled latency (Pi-puck <-> pc and pc <-> robot)
2) The computer establishes a WiFi connection with both the Pi-puck and the e-puck2 robot.
:''Advantages'':
:- only one connection type needed, easier to handle
:''Disadvantages'':
:- doubled latency (Pi-puck <-> pc and pc <-> robot)
3) The computer establishes a WiFi connection with the Pi-puck and then the Pi-puck is in charge of controlling the robot via I2C based on the data received from the computer controller.
:''Advantages'':
:- less latency involved
:- less number of connections to handle
:- depending on your algorithm, it would be possible to initially develop the controller on the computer (easier to develop and debug) and then transfer the controller directly to the Pi-puck without the need to change anything related to the control of the robot via I2C
The following figure summarizes these 3 options:<br/>
First of all you should update to the last version of the demos and scripts released with the system that you can use to start playing with the Pi-puck extension and the robot.<br/>
To update the repository follow these steps:<br/>
1. go to the directory <code>/home/pi/Pi-puck</code><br/>
2. issue the command <code>git pull</code><br/>
Then to update some configurations of the system:<br/>
1. go to the directory <code>/home/pi/Pi-puck/system</code><br/>
2. issue the command <code>./update.sh</code>; the system will reboot.<br/>
You can find the Pi-puck repository here [https://github.com/gctronic/Pi-puck https://github.com/gctronic/Pi-puck].<br/>
==Audio recording==
Use the <code>arecord</code> utility to record audio from the onboard microphone. The following example shows how to record an audio of 2 seconds (<code>-d</code> parameter) and save it to a wav file (<code>test.wav</code>):<br/>
You can also specify a rate of 48 KHz with <code>-r48000</code>
==Audio play==
Use <code>aplay</code> to play <code>wav</code> files and <code>mplayer</code> to play <code>mp3</code> files.
==Battery reading==
==Example==
An example showing how to measure both the battery of the robot and the battery of the Pi-puck extension is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/battery/</code>.<br/>
The first time you need to change the mode of the script in order to be executable with the command <code>sudo chmod +x read-battery.sh</code>.<br/>
Then you can start reading the batteries value by issueing <code>./read-battery.sh</code>.; this demo will print the batteries values (given in Volts) on the terminal.
==WiFi configuration==
The RGB panel can be controlled through either ASCII or binary commands. The following example illustrates the sequence of commands that must be
Specify your network configuration in the file <code>/etc/wpa_supplicant/wpa_supplicant-wlan0.conf</code>.<br/>
issued to turn on the LED0 at maximum brightness (all 3 R,G and B at maximum) using a terminal and the e-puck programmed with the standard firmware: <br/>
You can have more than one <code>network</code> parameter to support more networks. For more information about ''wpa_supplicant'' refer to [https://hostap.epitest.fi/wpa_supplicant/ https://hostap.epitest.fi/wpa_supplicant/].
where in the first line ''W'' is the command (I2C write), ''176'' is the I2C address of the RGB panel (fixed), ''0'' is the register address and ''128'' the brightness value. The last line contains a special command that is sent to the module when it's required to update the LEDs and IRs with the new values; this means that even if the first command is sent to the RGB panel, nothing will change until the last command is sent.
Once the configuration is done, you can also connect to the Pi-puck with <code>SSH</code>. If you are working in Windows you can use [https://www.putty.org/ PuTTY].
The binary version (a bit faster), using the ''-w'' command, of the previous sequence is:
<pre>
... init communication ...
===How to know your IP address===
sprintf(buffer, 5, "%c%c%c%c",-‘W’, 176, 0, 128);
A simple method to know your IP address is to connect the USB cable to the Pi-puck extension and issue the command <code>ip a</code>; from the command's result you will be able to get you current assigned IP address.
If you prefer to know your IP address remotely (without connecting any cable) then you can use <code>nmap</code>.<br/>
... send buffer ...
For example you can search all connected devices in your network with the following command: <code>nmap 192.168.1.*</code>. Beware that you need to specify the subnet based on your network configuration.<br/>
</pre>
From the command's result you need to look for the hostname <code>raspberrypi</code>.<br/>
If you are working in Windows you can use the [https://nmap.org/zenmap/ Zenmap] application.
==File transfer==
===USB cable===
You can transfer files via USB cable between the computer and the Pi-puck extension by using on of the <code>zmodem</code> protocol.<br/>
The <code>lrzsz</code> package is pre-installed in the system, thus you can use the <code>sx</code> and <code>rx</code> utilities to respectevely send files to the computer and receive files from the computer.<br/>
Example of sending a file to the computer using the <code>Minicom</code> terminal program:<br/>
1. in the Pi-puck console type <code>sx --zmodem fliename.ext</code>. The transfer should start automatically and you'll find the file in the home directory.<br/>
<!--2. to start the transfer type the sequence <code>CTRL+A+R</code>, then chose <code>xmodem</code> and finally enter the name you want to assign to the received file. You'll find the file in the home directory.<br/>-->
Example of receiving a file from the computer using the <code>Minicom</code> terminal program:<br/>
1. in the Pi-puck console type <code>rx -Z</code><br/>
2. to start the transfer type the sequence <code>CTRL+A+S</code>, then chose <code>zmodem</code> and select the file you want to send with the <code>spacebar</code>. Finally press <code>enter</code> to start the transfer.<br/>
===WiFi===
The Pi-puck extension supports <code>SSH</code> connections.<br/>
To exchange files between the Pi-puck and the computer, the <code>scp</code> tool (secure copy) can be used. An example of transferring a file from the Pi-puck to the computer is the following:<br/>
If you are working in Windows you can use [https://www.putty.org/ PuTTY].
==Image streaming==
==Bluetooth LE==
An example of a ''BLE uart service'' is available in the Pi-puck repository; you can find it in the directory <code>/home/pi/Pi-puck/ble/</code>.<br/>
To start the service you need to type: <code>python uart_peripheral.py</code>.<br/>
Then you can use the ''e-puck2-android-ble app'' you can find in chapter [https://www.gctronic.com/doc/index.php?title=e-puck2_mobile_phone_development#Connecting_to_the_BLE Connecting to the BLE] in order to connect to the Pi-puck extension via BLE. Once connected you'll receive some dummy data for the proximity values and by clicking on the motion buttons you'll see the related action printed on the Pi-puck side. This is a starting point that you can extend based on your needs.
=Operating system=
The system is based on Raspbian Stretch and can be downloaded from the following link [https://projects.gctronic.com/epuck2/PiPuck/pi-puck-os_16.12.19.zip pi-puck-os_16.12.19.zip].
When booting the first time, the first thing to do is expanding the file system in order to use all the available space on the micro sd:<br/>
1. <code>sudo raspi-config</code><br/>
2. Select <code>Advanced Options</code> and then <code>Expand Filesystem</code><br/>
3. reboot
==e-puck2 camera configuration==
The e-puck2 camera need to be configured through I2C before it can be used. For this reason a Python script is called at boot that detects and configures the camera. The script resides in the Pi-puck repository installed in the system (<code>/home/pi/Pi-puck/camera-configuration.py</code>), so beware to not remove it.
If the robot is plugged after the boot process is completed, you need to call manually the Python configuration script before using the camera by issueing the command <code>python3 /home/pi/Pi-puck/camera-configuration.py</code>.
In order to automatically run the script at boot, the <code>/etc/rc.local</code> was modified by adding the call to the script just before the end of the file.
==Power button handling==
The power button press is handled by a background service (<code>systemd</code>) started automatically at boot. The service description file is located in <code>/etc/systemd/system/power_handling.service</code> and it calls the <code>/home/pi/power-handling/</code> program. Beware to not remove neither of these files.<br/>
The source code of the power button handling program is available in the Pi-puck repository and is located in <code>/home/pi/Pi-puck/power-handling/power-handling.c</code>.
==Desktop mode==
The system starts in console mode, to switch to desktop (LXDE) mode issue the command <code>startx</code>.
===Camera viewer===
A camera viewer called <code>luvcview</code> is installed in the system. You can open a terminal and issue simply the command <code>luvcview</code> to see the image coming from the robot camera.
==VNC==
[https://www.realvnc.com/en/ VNC] is a remote control desktop application that lets you connect to the Pi-puck from your computer and then you will see the desktop of the Pi-puck inside a window on your computer. You'll be able to control it as though you were working on the Pi-puck itself.<br/>
VNC is installed in the system and the ''VNC server'' is automatically started at boot, thus you can connect with ''VNC Viewer'' from your computer by knowing the IP address of the Pi-puck (refer to section [https://www.gctronic.com/doc/index.php?title=Pi-puck#How_to_know_your_IP_address How to know your IP address]).<br/>
Notice that the ''VNC server'' is started also in console mode.
==I2C communication==
The communication between the Pi-puck extension and the robot is based on I2C. The system is configured to exploit the I2C hardware peripheral in order to save CPU usage, but if you need to use the software I2C you can enable it by modifying the <code>/boot/config.txt</code> file and removing the <code>#</code> symbol (comment) in front of the line with the text <code>dtparam=soft_i2c</code> (it is placed towards the end of the file).
==Audio output configuration==
You can enable or disable audio output by modifying the <code>config.txt</code> file in the <code>boot</code> partition.<br/>
To enable audio output insert the line: <code>gpio=22=op,dh</code><br/>
To disable audio output insert the line: <code>gpio=22=op,dl</code><br/>
If you don't need to play audio files it is suggested to disable audio output in order to save power.
=ROS=
ROS Kinetic is integrated in the Pi-puck system.<br/>
A ROS node developed to run in the Pi-puck is available for both <code>CPP</code> and <code>Python</code>, the communication system is based on the third architecture shown in chapter [https://www.gctronic.com/doc/index.php?title=Pi-puck#Wireless_remote_control Wireless remote control]; a more detailed schema is shown below:<br/>
The ROS workspace is located in <code>~/rosbots_catkin_ws/</code><br/>
The e-puck2 ROS driver is located in <code>~/rosbots_catkin_ws/src/epuck_driver_cpp/</code><br/>
Remember to follow the steps in the section [http://www.gctronic.com/doc/index.php?title=Pi-puck#Requirements Requirements ] and section [https://www.gctronic.com/doc/index.php?title=Pi-puck#Demos_and_scripts_update Demos and scripts update], only once.<br/>
The PC (if used) and the Pi-puck extension are supposed to be configured in the same network.
==Running roscore==
<code>roscore</code> can be launched either from the PC or directly from the Pi-puck.<br/>
Before starting roscore, open a terminal and issue the following commands:
where <code>pipuck-ip</code> is the IP of the Pi-puck extension and <code>roscore-ip</code> is the IP of the machine that runs <code>roscore</code> (can be the same IP if <code>roscore</code> runs directly on the Pi-puck).
To start the e-puck2 ROS node issue the command:<br/>
The last version of the e-puck2 ROS node can be downloaded from the git: <code>git clone -b pi-puck https://github.com/gctronic/epuck_driver_cpp.git</code><br/>
A Python version developed by the York University can be found here [https://github.com/yorkrobotlab/pi-puck-ros https://github.com/yorkrobotlab/pi-puck-ros].
=OpenCV=
OpenCV 3.4.1 is integrated in the Pi-puck system.
=York Robotics Lab Expansion Board=
The York Robotics Lab developed an expansion board for the Pi-puck extension that includes: 9-DoF IMU, 5-input navigation switch, RGB LED, XBee socket, 24-pin Raspberry Pi compatible header. For more information have a look at [https://pi-puck.readthedocs.io/en/latest/extensions/yrl-expansion/ https://pi-puck.readthedocs.io/en/latest/extensions/yrl-expansion/].<br/>
# <code>python3 pipuck-library-test.py -x</code> Once started, press in sequence up, down, left, right, center to continue the demo.
==Assembly==
The assembly is very simple: place the YRL expansion board on top of the Raspberry Pi and then connect them with the provided screws. Once they are connected, you can attach both on top of the Pi-puck extension.<br/>
In this section it is explained how to send data from the Pi-puck to the computer using XBee modules Series 1.
The XBee module mounted on the YRL expansion must be programmed with the <code>XBEE 802.15.4-USB ADAPTER</code> firmware; this can be done with the [http://www.digi.com/products/wireless-wired-embedded-solutions/zigbee-rf-modules/xctu XTCU software]. With XTCU be sure to program also the same parameters on both modules in order to be able to communicate between each other: <code>Channel</code> (e.g. <code>C</code>), <code>PAN ID</code> (e.g. <code>3332</code>), <code>DH = 0</code>, <code>DL = 0</code>, <code>MY = 0</code>.
Some Python examples ara available in the [https://github.com/yorkrobotlab/pi-puck-expansion-board YRL Expansion Board GitHub repository] that can be used to communicate with the XBee module mounted on the YRL expansion. These examples are based on the [https://github.com/digidotcom/xbee-python Digi XBee Python library] that can be installed with the command <code>pip3 install digi-xbee</code>. This library requires the XBee module to be configured in API mode; you can setup this mode following these steps:
Now connect the second module to the computer and run XTCU, select the console view and open the serial connection. Then run the [https://projects.gctronic.com/epuck2/PiPuck/xbee-send-broadcast.py xbee-send-broadcast.py] example from the Pi-puck by issuing the command: <code>python3 xbee-send-broadcast.py</code>. From the XTCU console you should receive <code>Hello Xbee World!</code>.
For more information refer to [https://pi-puck.readthedocs.io/en/latest/extensions/yrl-expansion/xbee/ https://pi-puck.readthedocs.io/en/latest/extensions/yrl-expansion/xbee/].
=Time-of-Flight Distance Sensor add-on=
=Videos=
The Pi-puck extension integrates six sensor board sockets that can be used to add up to six VL53L1X-based distance sensor add-ons. The Pi-puck equipped with these add-ons is shown in the following figure:<br/>
For more information have a look at [https://pi-puck.readthedocs.io/en/latest/extensions/tof-sensor/#time-of-flight-distance-sensor https://pi-puck.readthedocs.io/en/latest/extensions/tof-sensor/#time-of-flight-distance-sensor].
<font style="color:red"> Beware that once the socket for the ToF add-on sensor '''3''' is soldered on the pi-puck extension, you are no more able to connect the HDMI cable.</font>
The robot changes color basing itself on what his small camera sees, just like a real chameloen. This system is based on the standard e-puck on the bottom, the new 3x3 RGB display on top and a proper demo.<br/>
You can download the source code of this demo in the following link [https://projects.gctronic.com/rgb-panel/epuck-demo4.zip epuck-demo-chamaleon].
==Communicate with the ToF sensors==
{{#ev:youtube|pJVS-9sMiVY}}
In order to communicate with the sensors you can use the <code>multiple-i2c-bus-support</code> branch of the [https://github.com/pimoroni/vl53l1x-python vl53l1x-python] library from [https://shop.pimoroni.com/ Pimoroni]. To install this library follow these steps:
Every LED is independent from each other, so it's possible to turn on the LEDs with different colors in the RGB color space (additive color mixing), as shown in the following figures.
The infrareds are thought as identification sensors, this means that the robots can be recognized by an external device such as a camera observing their combination of infrareds turned on and off; for instance using 8 IRs it's possible to identify 256 different robots.
The communication between the e-puck and the module is via the I2C bus. Color commands are sent from the robot to the RGB panel (nothing is sent in the opposite way); this let us, for example, program the robot with a pre-fixed sequence of commands to send to the panel, resulting in a color animation. Other more elaborate demos could be implemented, reacting for example to the environment and nearby robots.
Another possibility is to develop a demo running on a computer and connecting the computer to the e-puck through Bluetooth (the e-puck and the module are connected through I2C as before); in practice the robot receives commands from the PC and forwards them to the RGB panel. This forwarding is implemented in the e-puck firmware, presented afterwards.
Electrical schema
The circuit diagram of the rgb panel e-puck extension is available to the community on the following link electrical schema.
Software
E-puck firmware
In order to play with the RGB extension for the e-puck robot you need to load the official e-puck firmware and set the selector on position 3 (advanced sercom protocol), refer to section E-Puck Standard firmware. Basically the firmware contains a command to setup the color of each led and the state of each infrared sensor; in particular there are two commands (binary mode): 'W' and 'w'; the first one is used to set a single led or infrared sensor, the second is used to set all actuators at once.
RGB panel firmware
Also the module requires a firmware running on it in order to handle the I2C communication and interpret the commands needed to turn on and off the sensors and color leds. The firmware can be downloaded from the following links (panel-MPLAB, panel-hex).
Demo - PC side
A basic demo running on a computer was developed to control manually all the LEDs color and IRs state through a Bluetooth connection. The application is implemented with Qt. A snapshot of this demo is shown hereafter:
To play with the e-puck2 robot and RGB extension you can run the same PC side application that is used with the e-puck1. In this case the e-puck2 robot must be programmed with the factory firmware and the selector must be placed in position 3.
Beware that in order to change the selector postion, both the e-puck2 and RGB panel must have the selector in the same position, this means that if you want the position 3 selected, then both the selector of the robot and the selector of the RGB panel must be placed in position 3.
If you want to control the RGB extension directly from the e-puck2, then you can do it by using the I2C bus (see chapter Registers). An example is provided to help you getting started, have a look at the following repository https://github.com/e-puck2/e-puck2_rgb_panel.
Programming
Registers
The LEDs and IRs are controlled by writing appropriate registers; the value within the registers represents the duty cycle that a LED/IR will reach, that is its brightness. The following table shows the registers used to configure the various LEDs and IRs.
X
RedX
BlueX
GreenX
IRX
Parameter registers
0
0x00
0x08
0x10
0xA4
1
0x01
0x09
0x11
0xA5
2
0x02
0x0A
0x12
0xA6
3
0x03
0x0B
0x13
0xA7
4
0x04
0x0C
0x14
0xA8
5
0x05
0x0D
0x15
0xA9
6
0x06
0x0E
0x16
0xAA
7
0x07
0x0F
0x17
0xAB
8
0x92
0x93
0x94
-
Example
The RGB panel can be controlled through either ASCII or binary commands. The following example illustrates the sequence of commands that must be
issued to turn on the LED0 at maximum brightness (all 3 R,G and B at maximum) using a terminal and the e-puck programmed with the standard firmware:
W, 176, 0, 128 [set red led0 max]
W, 176, 8, 128 [set blue led0 max ]
W, 176, 16, 128 [set green led0 max]
W, 176, 145, 1 [set command register (command terminator)]
where in the first line W is the command (I2C write), 176 is the I2C address of the RGB panel (fixed), 0 is the register address and 128 the brightness value. The last line contains a special command that is sent to the module when it's required to update the LEDs and IRs with the new values; this means that even if the first command is sent to the RGB panel, nothing will change until the last command is sent.
The binary version (a bit faster), using the -w command, of the previous sequence is:
The robot changes color basing itself on what his small camera sees, just like a real chameloen. This system is based on the standard e-puck on the bottom, the new 3x3 RGB display on top and a proper demo.
You can download the source code of this demo in the following link epuck-demo-chamaleon.
