Raspi and EV3-G

Error Messages so far

raspberry pi device added succesfuly but failed to connect

Connection failed: _blueman.RFCOMMError: Failed to get rfcomm channel

Paired successfully but this device has no services which can be used with raspberry pi

Pairing ev3 and Raspi

Pairing and connecting is easy using X11.

bluetooth-agent command do not exist on Jessie. Use bluetoothctl with the following script shown on Stackechange:

sudo bluetoothctl <<EOF
power on
discoverable on
pairable on
agent NoInputNoOutput
default-agent 
EOF

bluetoothctl
power on
discoverable on
scan on

trust <ev3 address>
pair <ev3 address>
agent on OR default-agent
devices
quit

Device 24:71:89:BA:DA:61 ev3dev
Device 00:16:53:53:64:E1 EV3

It helps to restart Ev3.

The file /etc/bluetooth/rfcomm.conf

rfcomm0 {
  # Automatically bind the device at startup
  bind no;
  # Bluetooth address of the device
  device 00:16:53:53:64:E1 ;
  # RFCOMM channel for the connection
  channel 2;
  # Description of the connection
  comment "This is Device EV3's serial port.";
}

[To establish Bluetooth] connection, need to create the serial device that binds to the paired Ev3 robot:

sudo rfcomm connect rfcomm0  00:16:53:53:64:E1

or use

sudo rfcomm bind /dev/rfcomm0  00:16:53:53:64:E1 1

where the last number is the communication channel. It needs to be unique.

Transmitting From EV3-G To Raspberry Pi

Two simple scripts to send data to Raspberry Pi.

#hackster.io -> Raspberry Pi Lego Mindstorms ev3 bluetooth
import serial
import time
EV3 = serial.Serial('/dev/rfcomm0')
print("Listening to")
try:
    while True:
        n = EV3.inWaiting()
        if n != 0:
            s = EV3.read(n)
            print( s )
            for n in s:
                print( "x%02X" % (n), end=' ' )
                #print( chr( int(n) ) )
            print()
        time.sleep(0.5)
except KeyboardInterrupt:
    pass
EV3.close()

The received data looks like

b'\x12\x00\x01\x00\x81\x9e\x07Status\x00\x04\x00Hei\x00'
x12 x00 x01 x00 x81 x9E x07 x53 x74 x61 x74 x75 x73 x00 x04 x00 x48 x65 x69 x00

Transmitting From Raspberry Pi To EV3-G

First start the Python script on the Raspberry Pi and then run the EV3 code.

Multiple hellos.

#! /usr/bin/env/ python3
import serial
import time
import EV3BT

EV3 = serial.Serial('/dev/rfcomm0')
s = EV3BT.encodeMessage(EV3BT.MessageType.Text, 'abc', 'Have fun')
for i in range(10):
    print(i)
    s = EV3BT.encodeMessage(EV3BT.MessageType.Text, 'abc', 'Have fun'+ str(i))
    #s = EV3BT.encodeMessage(EV3BT.MessageType.Numeric, 'abc', 123)
    #s = EV3BT.encodeMessage(EV3BT.MessageType.Text, 'abc', 'Have fun')
    print( EV3BT.printMessage(s) )
    EV3.write(s)
    time.sleep(1)
EV3.close()

The brick says once Hello' and after that wants to connect to raspi. If the wrong password is given, the Python code will shutdown. The update in the EV3-G's Bluetooth command do not work.

Some links

• http://www.geekdroppings.com/2018/01/21/raspberry-pi-and-the-lego-ev3-connected-by-bluetooth/
• https://www.hackster.io/KKE/raspberry-pi-lego-mindstorms-ev3-bluetooth-communication-aa42e2
• https://siouxnetontrack.wordpress.com/2013/09/27/connecting-the-pc-to-our-ev3/
• https://gipprojects.wordpress.com/2013/11/29/using-python-and-raspberry-pi-to-communicate-with-lego-mindstorms-ev3/
• https://ev3lessons.com/en/ProgrammingLessons/beyond/EV3PiLight.pdf
• https://ev3lessons.com/en/ProgrammingLessons/beyond/EV3PiCommunicator.pdf
• http://www.abrowndesign.com/2018/10/25/sending-bluetooth-messages-from-raspberry-pi-to-lego-ev3-stock-firmware/
• https://github.com/lehoff/ev3bt/

• 

  Maksym Shyte @ http://www.geekdroppings.com/2018/01/21/raspberry-pi-and-the-lego-ev3-connected-by-bluetooth/

• 

  Koen Kempeneers @ https://www.hackster.io/KKE/raspberry-pi-lego-mindstorms-ev3-bluetooth-communication-aa42e2

• 

  Hans Odenthal @ https://siouxnetontrack.wordpress.com/2013/09/27/connecting-the-pc-to-our-ev3/