Raspi and EV3-G

From wikiluntti

Projects

Raspberry Pi Bluetooth controlled steerable robot

CV2:

  • Pacman
  • Maze
  • Swarm robots

Gyro controlled

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 bind 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.


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


Some links


Retrieved from "https://wiki.luntti.net/index.php?title=Raspi_and_EV3-G&oldid=1940"