Connecting Raspberry Pi to another device via USB port

Question

I am trying to connect the Raspberry Pi to a microcontroller using the USB Port. I have used the device many times and I know how the protocol works. It should reply after receiving the message that I am sending.

I am using a USB cable connected to a null cable like this one.

I am running the following python program (I am running Python 3.2):

import serial

port =serial.Serial(
    "/dev/ttyUSB0",
    baudrate=57600,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS,
    writeTimeout = 0,
    timeout = 10)

data=bytes([0x0c,0x80,0x09,0x00,0xf0,0xce,0x61,0x9d,0x01,0x00,0x01,0x00,0x00,0x00]) 

print(port.isOpen()) 
print("Port opened...") 
port.write(data) 
print("Data sent")

while True:
    print("inside while")
    response=port.read(8)
    print(response)
    print ("Data Received")
    break

Raspberry Pi is not receiving anything, just timeout.

In order to test the program I ran it on my windows 7 computer running Python 3.2 changing the port to the right COM. I used the same cables. It is getting the right answer from the device and printing it.

I am sure the baudrates are right.

Any help would be appreciated.

Answer 1

I just got the solution.

I updated/upgraded wheezy first. Then opened the port like this:

port =serial.Serial(
    "/dev/ttyUSB0",
    baudrate=57600,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS,
    writeTimeout = 0,
    timeout = 10,
    rtscts=False,
    dsrdtr=False,
    xonxoff=False)

Answer 2

I am no expert with PySerial, but shouldn't the string "-dev-ttyUSB0" be "/dev/ttyUSB0" ?