Python Serial library for RaspberryPi2 tutorial/command list

Question

I have a problem with using the UART on RPi2.

I tried every program found on the internet but nothing works. I checked every baud rate of my two BT modules but whatever code I use I've got errors like this:

Error 1:

Traceback (most recent call last):   File "Serial2.py", line 6, in
<module>
    serial_line = ser.readline()   File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 449, in
read
    buf = os.read(self.fd, size-len(read)) OSError: [Errno 11] Resource temporarily unavailable

Error 2:

Traceback (most recent call last):
  File "Serial2.py", line 6, in <module>
    serial_line = ser.readline()
  File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 449, in read
    buf = os.read(self.fd, size-len(read))
OSError: [Errno 11] Resource temporarily unavailable

Error 3:

Traceback (most recent call last):   File "Serial.py", line 7, in
<module>
    rcv = port.read()   File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 456, in
read
    raise SerialException('device reports readiness to read but returned no data (device disconnected?)')
serial.serialutil.SerialException: device reports readiness to read
but returned no data (device disconnected?)

Err1 code:

import serial

    port = serial.Serial("/dev/ttyAMA0", baudrate=115200, timeout=3.0)

    while True:
        port.write("\r\nSay something:")
        rcv = port.read()
        port.write("\r\nYou sent:" + rcv)

Err2&3 code:

import serial, time

ser = serial.Serial('/dev/ttyAMA0', 9600)

while 1:
    serial_line = ser.readline()

    print(serial_line)
    time.sleep(300)
ser.close()

I'm using ArduinoRC app (Terminal) to send data.

Would you help me and/or send a link to a good command list please ?

Answer 1

I also had a lot of problems with it... But today I found a solution from this site: http://m.instructables.com/id/Read-and-write-from-serial-port-with-Raspberry-Pi/

#!/usr/bin/env python

import time 
import serial 

ser = serial.Serial( port='/dev/ttyUSB0', 
    baudrate = 9600, 
    parity=serial.PARITY_NONE, 
    stopbits=serial.STOPBITS_ONE, 
    bytesize=serial.EIGHTBITS, 
    timeout=1 
) 
counter=0

while 1: 
    x=ser.readline() 
    print x

And the code worked, only you need to change the

/dev/ttyUSB0

To:

/dev/ttyAMA0

Like this (this is the code that worked):

EDIT: reformatted the code:

#!/usr/bin/env python

import serial
import time

ser = serial.Serial(
    port='/dev/ttyAMA0',
    baudrate = 9600,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS,
    timeout=0.2
)
counter=0

while 1:
    x=ser.readline()
    print x

Ps: I used an HC-06 module, also be sure you have disabled the boot sequence on the serial port: open terminal, sudo raspi-config

And then go to advanced options and there will be something like boot on serial, you need to disable that.

Kind regards Michielvk

Answer 2

According to http://download.chip45.com/BTM222_DataSheet.pdf the factory settings of the UART are as follows

Baud rate: 19200 bps
Data bit: 8
Parity: none
Stop bit: 1