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Raspberry Pi Forum Help with c and wiringpi library
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  • raspberry
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Related

Help with c and wiringpi library

wallarug
wallarug over 13 years ago

I need some help writing a TCP server (like the one below) in "c" rather than python.  REASON: I need to write data to my Gertboard through the Raspberry Pi's UART RX/TX GPIO header.  I can't find any examples of how to do the Raspberry Pi GPIO with wiringpi.

 

Below is my current Python Script for writing data to an Arduino ATMEGA connected through the USB port:

 

from time import sleep

import sys

import socket

while True:

    s = socket.socket()         # Create a socket object

    host = '192.168.12.24'          # Get local machine name

    port = 9999                 # Reserve a port for your service.

 

 

 

 

    import serial

    DEVICE = '/dev/ttyACM0' # the arduino serial interface (use dmesg when connecting)

    ##DEVICE = 'COM12'

    BAUD = 9600

    ser = serial.Serial(DEVICE, BAUD)

    try:

        print "Server started on", str(host) + ":" + str(port)

        print 'Waiting for clients...'

    

        s.bind((host, port))        # Bind to the port

        s.listen(5)                 # Now wait for client connection.

        c, addr = s.accept()     # Establish connection with client.

        print 'Got connection from', addr

        while True:

            msg = c.recv(3) # get 3 bytes from the TCP connection

            ser.write(msg)  # write the 3 bytes to the serial interface

            #print msg

            if msg == "":

                c.shutdown(socket.SHUT_RDWR)

                c.close()

                print "Lost connection with"+ str(addr) +"! Restarting server..."

                sleep(2)

                    break

    except KeyboardInterrupt:

        print "[ALERT]  Closing shell...  [ALERT]"

        c.shutdown(socket.SHUT_RDWR)

        c.close()

        ser.close()

        sys.exit("Application forcibly halted!")

 


Is there any way someone can please make me a c version and then incorperate the Gertboard's ATMEGA device?

 

Thanks in advance.

Attachments:
TCP - Beta 1.7.py.zip
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  • anhtien
    anhtien over 13 years ago

    Hi Fergus,

    I posted a couple of WiringPi examples on my blog (http://rpidude.blogspot.com/), you are welcome to look at the last two experiments (Temp sensor, Motorshield) and see if you can port the client/server code that Michael refers to.  WiringPi is easier than you think.

    Good luck,

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  • mconners
    mconners over 13 years ago in reply to anhtien

    Nice set of samples you have there. Great resource for people looking for info.

     

    Mike

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  • mconners
    mconners over 13 years ago in reply to anhtien

    Nice set of samples you have there. Great resource for people looking for info.

     

    Mike

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  • wallarug
    wallarug over 13 years ago in reply to mconners

    So I write the script like an Arduino Sketch?

     

    What is the syntax to send to the Serial device connected to the UART GPIO pins?

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  • anhtien
    anhtien over 13 years ago in reply to mconners

    Thank you, Mike, with all your pointers I think you teach a man how to fish with a net instead of just a fishing rod.  You were correct on /dev/ttyAMA0 as serial device (/etc/inittab).  Gordons Projects actually has the serial library that one could very quickly convert from the Arduino sketch sample above to WiringPi C program, the comments section is helpful too.

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  • mconners
    mconners over 13 years ago in reply to wallarug

    Fergus Byrne wrote:

     

    So I write the script like an Arduino Sketch?

     

    What is the syntax to send to the Serial device connected to the UART GPIO pins?

     

    I'm not really clear what you are asking here.

     

    I was advocating moving away from wiring and just writing a c executable, although anhtien, has posted a link to the wiring serial library, which looks pretty simple to use, you would just specify the device as ttyAMA0, and not worry about the fact that it xmits over the gpio pins, the os takes care of that for you.

     

    I must plead ignorance on whether you can access the socket library from wiringpi or not, as I said I was advocating a c exe not a sketch.

     

    If the python code you posted originally works for you as is, you should just be able to change ttyACM0 to ttyAMA0 and it will then work using the gpio tx and rx pins, you don't need to worry about the low level programming, again the os takes care of it all.

     

     

    The syntax will vary depending on the method you use. If you use python, just specify ttyAMA0 and use as is, if you use wiring, then use the wiring serial library, if you make a c executable, then you have to open the device and set the ioctl to get the baud rate you need.

     

    Good luck.

     

    Mike

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  • wallarug
    wallarug over 13 years ago in reply to mconners

    Michael,

     

    Have a look at this post by me here:

     

    http://www.raspberrypi.org/phpBB3/viewtopic.php?p=224962#p224962

     

    I hope this clears up what I want to do.  If not please let me know.

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  • mconners
    mconners over 13 years ago in reply to wallarug

    I have a few questions:

     

    1) Why do you need to use wiringpi? Or is python acceptable?

     

    2) Have you done the following on the ras Pi? :

    -------------------------------------------------------------------------------------

    First, disable the boot up and diagnostic output to the serial port.

    sudo vi /boot/cmdline.txt

    and remove the two options referring to the serial port.

    So, this

    dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

    becomes this

    dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

     

     

    Second, disable the login prompt

    sudo vi /etc/inittab

    find the line near the end

    T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

    and delete it or comment it out by putting a # at the start of the line.

    ---------------------------------------------------------------------------------------------------------

     

    If you haven't then the OS has control of the serial port and won't let you access it.

     

    3) Is the ATMega chip on the gertboard programmed?

    Meaning have you got your or any sketch running on it?

    If not then the ATMega is not going to do anything.

     

     

    From what I can gather out of reading your code you:

     

    Monitor the tcp connection for data

    When data is present you read 3 bytes

    You retransmit the 3 bytes to the Arduino via the serial port

     

    So you need to have code running on the ATMega chip to receive the 3 bytes of data

     

    and on the PI you need to disble the serial port as shown above in step 2, that is very important, you may need to run your python code as root, or do sudo as well

     

    change the following in your python script

     

    import serial

        DEVICE = '/dev/ttyACM0' # the arduino serial interface (use dmesg when connecting)

        ##DEVICE = 'COM12'

        BAUD = 9600

     

    to

     

    import serial

        DEVICE = '/dev/ttyAMA0' # the arduino serial interface (use dmesg when connecting)

        ##DEVICE = 'COM12'

        BAUD = 9600

     

    that is all you need to do, you don't have to worry about uarts or gpio or anything, the OS has abstracted all that for you and named the device ttyAMA0

     

    Hope this gets you on your way

     

    Mike

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  • wallarug
    wallarug over 13 years ago in reply to mconners

    1) Why do you need to use wiringpi? Or is python acceptable?

    From my research thus far I think the answer is "no".  I think that the python serial library can do the job for me.

     

    2) Have you done the following on the ras Pi? :

    -------------------------------------------------------------------------------------

    First, disable the boot up and diagnostic output to the serial port.

    sudo vi /boot/cmdline.txt

    and remove the two options referring to the serial port.

    So, this

    dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

    becomes this

    dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

     

    The options were never in there in the first place.  I checked if they were present (because I read somewhere that need to be done) but they weren't there.  I will get back to you after I boot up RPi in a minute.

     

     

    Second, disable the login prompt

    sudo vi /etc/inittab

    find the line near the end

    T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

    and delete it or comment it out by putting a # at the start of the line.

    ---------------------------------------------------------------------------------------------------------

    YES!  I know I did this one!  I did it as one of Gorden's suggestions o save memery.

     

    3) Is the ATMega chip on the gertboard programmed?

    Meaning have you got your or any sketch running on it?

    Yes.  I followed the instuctions on how to get blink to work and then modified to upload my sketch using the SPI interface.

     

    import serial

        DEVICE = '/dev/ttyAMA0' # the arduino serial interface (use dmesg when connecting)

        ##DEVICE = 'COM12'

        BAUD = 9600

    I tried that last night and the TCP connection did not spit-out errors but did not write to the Arduino or the ATMEGA on the Gertboard.

     

    I am going to have a look at everything you have suggested above and triple check it is all right.

     

    Thanks for the help.! imageimageimage

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  • wallarug
    wallarug over 13 years ago in reply to wallarug

    Ok, RPi is up and running...here are some results:

     

    nano /boot/cmdline.txt:

    dwc_otg.lpm_enable=0    root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

     

    nano /etc/inittab:

     

    #Spawn a getty on Raspberry Pi serial line

    ##T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

    nano /root/TCP.py:

     

    import serial

        DEVICE = '/dev/ttyAMA0' # the arduino serial interface (use dmesg when$

        ##DEVICE = 'COM12'

        BAUD = 9600

        ser = serial.Serial(DEVICE, BAUD)

     

    All seems good.  I think I might have to do a check with both my rev1 and rev2 boards (currently using rev1) due to the changes on that header from GPIO 0 to GPIO 2 and GPIO1 to GPIO3.

     

    I will continue experimenting.

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