e-puck2

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Hardware

Overview


The following figures show the main components offered by the e-puck2 robot and where they are physically placed:

Specifications

The e-puck2 robot maintains full compatibility with its predecessor e-puck (e-puck HWRev 1.3 is considered in the following table):

Feature e-puck1.3 e-puck2 Compatibility Additional
Size, weight 70 mm diameter, 55 mm height, 150 g Same form factor: 70 mm diameter, 45 mm, 130 g No e-jumper required
Battery, autonomy LiIPo rechargeable battery (external charger), 1800 mAh.
About 3 hours autonomy. Recharging time about 2-3h. 		Same battery; USB charging, recharging time about 2.5h. USB charging
Processor 16-bit dsPIC30F6014A @ 60MHz (15 MIPS), DSP core for signal processing 32-bit STM32F407 @ 168 MHz (210 DMIPS), DSP and FPU, DMA ~10 times faster
Memory RAM: 8 KB; Flash: 144 KB RAM: 192 KB; Flash: 1024 KB RAM: 24x more capable
Flash:~7x more capable
Motors 2 stepper motors with a 50:1 reduction gear; 20 steps per revolution; about 0.13 mm resolution Same motors
Wheels Wheels diamater = 41 mm
Distance between wheels = 53 mm 		Same wheels
Speed Max: 1000 steps/s (about 12.9 cm/s) Max: 1200 steps/s (about 15.4 cm/s) 20% faster
Mechanical structure Transparent plastic body supporting PCBs, battery and motors Same mechanics
Distance sensor 8 infra-red sensors measuring ambient light and proximity of objects up to 6 cm Same infra-red sensors
Front real distance sensor, Time of fight (ToF), up to 2 meter. 		ToF sensor
IMU 3D accelerometer and 3D gyro 3D accelerometer, 3D gyro, 3D magnetometer 3D magnetometer
Camera VGA color camera; typical use: 52x39 or 480x1 Same camera; typical use: 160x120 Bigger images handling
Audio 3 omni-directional microphones for sound localization
speaker capable of playing WAV or tone sounds 		4 omni-directional microhpones (digital) for sound localization
speaker capable of playing WAV or tone sounds 		+1 front microphone
LEDs 8 red LEDs around the robot, green body light, 1 strong red LED in front 4 red LEDs and 4 RGB LEDs around the robot, green light, 1 strong red LED in front 4x RGB LEDs
Communication RS232 and Bluetooth 2.0 for connection and programming USB Full-speed, Bluetooth 2.0, BLE, WiFi WiFi, BLE
Storage Not available Micro SD slot Micro SD
Remote Control Infra-red receiver for standard remote control commands Same receiver
Switch / selector 16 position rotating switch Same selector
Extensions Ground sensors, range and bearing, RGB panel, Gumstix extension, omnivision, your own All extension supported
Programming Free C compiler and IDE, Webots simulator, external debugger Free C compiler and IDE, Webots simulator, onboard debugger (GDB) Onboard debugger

This is the overall communication schema:

Documentation

Migrating from e-puck1.x to e-puck2

The e-puck2 robot maintains full compatibility with its predecessor e-puck, but there are some improvements that you should be aware of.

First of all the e-jumper, that is the small board that is attached on top of the e-puck1.x, isn't anymore needed in the e-puck2. The components available on the e-jumper are integrated directly in the robot board. On top of the e-puck2 you'll see a quite big free connector, this is used to attach the extensions board designed for the e-puck1.x that are fully compatible with the e-puck2; you must not connect the e-jumper in this connector.

Secondly you don't need anymore to unplug and plugin the battery for charging, but instead you can charge the battery directly by connecting the USB cable. If you want you can still charge the battery with the e-puck1.x external charger, in case you have more than one battery.

Moreover you don't need anymore a special serial cable (with probably an RS232 to USB adapter) to be able to communicate with the robot, but you can use the USB cable. Once connected to the computer a serial port will be available that you can use to easily exchange data with the robot.

Extensions

All the extensions (ground sensors, range and bearing, RGB panel, gumstix and omnvision) are supported by the e-puck2 robot, this means that if you have some extensions for the e-puck1.x you can still use them also with e-puck2.
For more information about using the gumstix extension with e-puck2 robot refer to http://www.gctronic.com/doc/index.php?title=Overo_Extension#e-puck2.

Getting Started

Meaning of the LEDs

The e-puck2 has three groups of LEDs that are not controllable by the user.


Top view of the e-puck2
  • Charger : RED if charging, GREEN if charge complete and RED and GREEN if an error occurs
  • USB : Turned ON if the e-puck2 detects a USB connection with a computer
  • STATUS : Turned ON if the robot is ON and OFF is the robot is OFF. When ON, gives an indication of the level of the battery. Also blinks GREEN if the program is running during a debug session.

Battery level indications (STATUS RGB LED):

  • GREEN if the system's tension is greater than 3.5V
  • ORANGE if the system's tension is between 3.5V and 3.4V
  • RED if the system's tension is between 3.4V and 3.3V
  • RED blinking if the system's tension is below 3.3V

The robot is automatically turned OFF if the system's tension gets below 3.2V during 10 seconds.

Finding the USB serial ports used

Two ports are created by the e-puck2's programmer when the USB cable is connected to the robot (even if the robot is turned off):

A third port could be available depending on the code inside the e-puck2's microcontroller. With the standard firmware a port named e-puck2 STM32F407 is created.

Windows

  1. Open the Device Manager
  2. Under Ports (COM & LPT) you can see the virtual ports connected to your computer.
  3. Do a Right-click -> properties on the COM port you want to identify.
  4. Go under the details tab and select Bus reported device description in the properties list.
  5. The name of the port should be written in the text box below.
  6. Once you found the desired device, you can simply look at its port number (COMX).

Linux

1. Open a terminal window (ctrl+alt+t) and enter the following command.
ls /dev/ttyACM*
2. Look for ttyACM0 and ttyACM1 in the generated list, which are respectively e-puck2 GDB Server and e-puck2 Serial Monitor.

Note : Virtual serial port numbering on Linux is made by the connections order, thus it can be different if another device using virtual serial ports is already connected to your computer.

Mac

1. Open a terminal window and enter the following command.
ls /dev/cu.usbmodem*
2. Look for two cu.usbmodemXXXX, where XXXX is the number attributed by your computer. You should find two names, more or less following in the numbering, which are respectively e-puck2 GDB Server and e-puck2 Serial Monitor.

Note : Virtual serial port numbering on Mac depends on the physical USB port used and the device. If you want to keep the same names, you must connect to the same USB port each time.

Software

PC interface


An interface running on a computer and connecting to the e-puck2 either through Bluetooth (selector position 3) or via USB (selector position 8) based on the advanced sercom protocol was developed; from this interface it's possible to have information about all the sensors, receive camera images and control the leds and motors. The source code is available from the repository https://github.com/e-puck2/monitor. Available executables:

On Linux remember to apply the configuration explained in the chapter Installation for Linux - Serial Port in order to access the serial port.

WiFi support

A dedicated WiFi version of the monitor application was developed to communicate with the robot through TCP protocol.
For more information about the communication protocol, refer to section WiFi communication protocol.
The source code can be downloaded with the command git clone -b wifi --recursive https://github.com/e-puck2/monitor.git
A Windows executable is available here Monitor WiFi for Windows.

Main microcontroller firmware

The robot is initially programmed with a firmware that includes many demos that could be started based on the selector position:

  • Selector position 0: Aseba
  • Selector position 1: Shell
  • Selector position 2: Read proximity sensors
  • Selector position 3: Asercom protocol v2 (BT)
  • Selector positoin 4: Range and bearing extension (receiver)
  • Selector position 5: Range and bearing extension (transmitter)
  • Selector position 6: ESP32 UART communication test
  • Selector position 7: ...
  • Selector position 8: Asercom protocol v2 (USB)
  • Selector position 9: Asercom protocol (BT)
  • Selector position 10: This position is used to work with the gumstix extension.
  • Selector position 11: Simple obstacle avoidance + some animation
  • Selector position 12: Hardware test
  • Selector position 13: LEDs reflect orientation of the robot
  • Selector position 14: Read magnetometer sensor
  • Selector position 15: ...

The source code is available in the git repo https://github.com/e-puck2/e-puck2_main-processor.
The pre-built firmware is available here e-puck2-firmware.

Flashing the main microcontroller

Refer to section Flashing the main microcontroller.

WiFi support

At the moment there is a separate firmware if the user want to use the WiFi; this firmware was specifically developed to transmit the camera image and sensors to the computer and receive commands from the computer (only motors and red LEDs are supported at the moment).
In the future the WiFi support will be integrated in the standard firmware.
The source code can be downloaded with the command git clone -b wifi --recursive https://github.com/e-puck2/e-puck2_main-processor.git
The pre-built firmware is available here e-puck2-firmware_wifi.

Library

The library contains all the functions needed to interact with the robot's sensors and actuators; the project includes also the basic standard firmware that shows how to use these functions.
A snapshot of the library can be donwloaded from e-puck2_main-processor_snapshot_16.02.18.zip.
Otherwise the latest version can be downloaded with the command: git clone --recursive https://github.com/e-puck2/e-puck2_main-processor.git
If you don't have git, you can issue the command: sudo apt-get install git.

Programmer firmware

This firmware is based on Black Magic Probe programmer/debugger.
The source code can be downloaded with the command git clone --recursive -b e-puck-2.0_E https://github.com/e-puck2/e-puck2-programmer
In order to build the firmware you need to issue the following commands form the main repo directory:
make clean
make PROBE_HOST=e-puck/2.0
The result is a bin file named blackmagic.bin that you can find in the src directory.
The pre-built firmware is available here programmer-firmware.bin; it is also available in dfu format here programmer-firmware.dfu.

Flashing the programmer

First of all to update the programmer's firmware you need to enter DFU mode (device firmware upgrade). To do it refer to section Using the DFU, in particular Note 2.
The programmer will be recognized as STM Device in DFU Mode device.

Linux

In order to update the programmer firmware you need an utility called dfu-util.
To install it issue the command sudo apt-get install dfu-util.
Then issue the following command to upload the firmware: sudo dfu-util -d 0483:df11 -a 0 -s 0x08000000 -D programmer-firmware.bin

Windows

For Windows users it is available an application called DfuSe released by STMicroelectronics. You can download it from DfuSe_V3.0.5.zip.
When the program is started, the programmer in DFU mode will be automatically detected as shown in figure 1. Then you need to open the compiled firmware by clicking on choose and then locating the file, as shown in figure 2. Now click on the upgrade button, a warning message will be shown, confirm the action by clicking on yes as shown in figure 3. If all is ok you'll be prompted with a message saying that the upgrade was successfull as shown in figure 4.

[1] [2] [3] [4]


Radio module firmware

The firmware support Bluetooth communication.
The source code can be downloaded with the command git clone --recursive https://github.com/e-puck2/esp-idf.git
In order to build the firmware you need to install the toolchain, refer to http://esp-idf.readthedocs.io/en/latest/get-started/#setup-toolchain. Once installed you can issue the command make flash from the directory Projects\ESP32_E-Puck_2 to build the firmware. For more information have a look at http://esp-idf.readthedocs.io/en/latest/get-started/#build-and-flash.
The pre-built firmware is available here esp32-firmware.zip.

Flashing the radio module

Refer to section Flashing the radio module.

WiFi support

At the moment there is a separate firmware if the user want to use the WiFi; this firmware was specifically developed to transmit the camera image and sensors to the computer and receive commands from the computer (only motors and red LEDs are supported at the moment).
In the future the WiFi support will be integrated in the standard firmware.
The source code can be downloaded with the command git clone -b wifi --recursive https://github.com/e-puck2/esp-idf.git
The pre-built firmware is available here esp32-firmware_wifi.zip.

Advanced usage

Configuring the Programmer's settings

The on-board programmer of the e-puck2 is based on the Blackmagic probe open source project firmware.
Some functionalities has been added on top of the original project to be able to control some functions of the robot, for example the power on or power off.

To access to the available commands of the programmer, it is needed to connect to the programmer with a GDB console.
To do so, you have to type the following command in a terminal window with the com port used by the 'e-puck2 GDB Server port of your e-puck2 : 

arm-none-eabi-gdb 
target extended-remote your_gdb_com_port

Once connected to the programmer with GDB, you can type 

monitor help

or 

mon help

to print the available commands of the programmer.

One command in particular is useful, which is mon select_mode. It is used to select in which mode the e-puck2 Serial Monitor com port will work.
mode 1 = the serial monitor is connected to the UART port of the main processor
mode 2 = the serial monitor is connected to the UART of the ESP32
mode 3 = the serial monitor works as a Aseba CAN to USB translator

The choice made for the mode is the only setting that is stored in a flash zone of the programmer, which means the choice is remembered, even if the robot is completely turned off.

Note : in mode 1 and 3, GDB can be used over the bluetooth connection of the e-puck2. But is is much slower than with USB and it doesn't work with Windows due to GDB limitations on this OS.

By being connected with GDB, you can also use the standard GDB command to program and debug the main processor of the e-puck2.

Using the DFU

To put the e-puck2 into DFU, it is needed to turn it on while keeping pressed the "407 boot" button located under the electronic card on the left side of the robot.
The robot will appear as "STM32 BOOTLOADER" in the USB devices.

Once in DFU, you can program it with dfu-util using the following command : 

dfu-util -d 0483:df11 -a 0 -s 0x08000000 -D your_firmware.bin

See the manual page of dfu-util for further information on how to use it.

Note: For windows, it is needed to install a libusbK driver for the DFU device.
You can use the Zadig program located in the Eclipse_e-puck2\Tools\ (if you installed Eclipse_e-puck2 package) to install it.
Follow the same procedure as explained above under the Installation drivers section using libusbK driver instead of USB Serial (CDC).

Note 2: It is also possible to put the programmer in DFU by contacting two pinholes together while inserting the USB cable (no need to turn on the robot).
It is used to update the firmware of the programmer.
The two pin holes are located near the USB connector of the e-puck2, see the photo below.


Location of the pin holes to put the programmer into DFU

WiFi communication protocol

The communication is based on TCP; the robot create a TCP server and wait for a connection.

Each packet is identified by an ID (1 byte). The following IDs are used to send data from the robot to the computer:

  • 0x00 = reserved
  • 0x01 = QQVGA color image packet (only the first segment includes this id); packet size (without id) = 38400 bytes; image format = RGB565
  • 0x02 = sensors packet; packet size (without id) = 104 bytes; the format of the returned values are based on the asercom protocol and are compatible with e-puck1.x:

  • Acc: raw axes values, between -1500 and 1500, resolution is +-2g
  • Acceleration: acceleration magnitude , between 0.0 and about 2600.0 (~3.46 g)
  • Orientation: between 0.0 and 360.0 degrees
    0.0 deg90.0 deg180 deg270 deg
  • Inclination: between 0.0 and 90.0 degrees (when tilted in any direction)
    0.0 deg90.0 deg
  • Gyro: raw axes values, between -32768 and 32767, range is +-250dps
  • Magnetometer: raw axes values, between -32760 and 32760, range is +-4912 uT (magnetic flux density expressed in micro Tesla)
  • Temp: temperature given in Celsius degrees
  • IR proximity: between 0 (no objects detected) and 4095 (object near the sensor)
  • IR ambient: between 0 (strong light) and 4095 (dark)
  • ToF distance: distance given in millimeters
  • Mic volume: between 0 and 4095
  • Motors steps: 1000 steps per wheel revolution
  • Battery:
  • uSD state: 1 if the micro sd is present and can be read/write, 0 otherwise
  • TV remote data: RC5 protocol
  • Selector position: between 0 and 15
  • Ground proximity: between 0 (no surface at all or not reflective surface e.g. black) and 1023 (very reflective surface e.g. white)
  • Ground ambient: between 0 (strong light) and 1023 (dark)
  • Button state: 1 button pressed, 0 button released
  • 0x03 = empty packet (only id is sent); this is used as an acknowledgment for the commands packet when no sensors and no image is requested

The following IDs are used to send data from the computer to the robot:

  • 0x80 = commands packet; packet size (without id) = 20 bytes:

  • request:
    • bit0: 0=stop image stream; 1=start image stream
    • bit1: 0=stop sensors stream; 1=start sensors stream
  • settings:
    • bit0: 1=calibrate IR proximity sensors
    • bit1: 0=disable onboard obstacle avoidance; 1=enable onboard obstacle avoidance (not implemented yet)
    • bit2: 0=set motors speed; 1=set motors steps (position)
  • left and right: when bit2 of settings field is 0, then this is the desired motors speed (-1000..1000); when 1 then this is the value that will be set as motors position (steps)
  • LEDs: 0=off; 1=on; 2=toggle
    • bit0: 0=LED1 off; 1=LED1 on
    • bit1: 0=LED3 off; 1=LED3 on
    • bit2: 0=LED5 off; 1=LED5 on
    • bit3: 0=LED7 off; 1=LED7 on
    • bit4: 0=body LED off; 1=body LED on
    • bit5: 0=front LED off; 1=front LED on
  • RGB LEDs: for each LED, it is specified in sequence the value of red, green and blue (0...100)
  • sound id: 0x01=MARIO, 0x02=UNDERWOLRD, 0x04=STARWARS, 0x08=4KHz, 0x10=10KHz, 0x20=stop sound

For example to receive the camera image (stream) the following steps need to be followed:
1) connect to the robot through TCP
2) send the command packet:

0x80 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00

3) read the ID (1 byte) and the QQVGA color image pakcet (38400 bytes)
4) go to step 3

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