树莓派python服务器未发送串行读/写命令

Question

I've got two servers (written in python) that are nearly identical in the way they handle serial communications on the Pi. However, one works and the other one doesn't and I can't seem to find the problem. I've hooked up a logic analyzer and the first server triggers the rx/tx properly when communicating serially, however, the second server will not trigger anything.

First (working) server - cut down to show only the serial:

import socket
import sys
import RPi.GPIO as GPIO
from serial import Serial

#HOST = ' ' # Symbolic name meaning all available interfaces
PORT = 8888 # Arbitrary non-privleged port
ser = 0

#accepts a command as a string, parameters separated by white space
def processData( data ):
    print ( "cmd : " + data).strip()
    parseData = data.split(" ")
    cmdLength = len(parseData)
    cmd = parseData[0]

    if cmd == "digitalWritePin":
        pin = parseData[1]
        state = parseData[2]
        #GPIO.setup(pin, GPIO.OUT) # SHOULD HAVE ALREADY BEEN DONE W/ A CONFIG!!!
        if state == '1':
            GPIO.output(int(pin), True)
        elif state == "0":
            GPIO.output(int(pin), False)
    elif cmd == "serialConfig":
        baudRate = int(parseData[1])
        timeOut = int(parseData[2])
        global ser
        ser = Serial('/dev/ttyAMA0', baudRate, timeout=timeOut)
    elif cmd == "serialWrite":
        serialcmd = parseData[1]
        writeBuff = data.split("serialWrite")
        #print writeBuff[1].strip(" ")
        ser.write(writeBuff[1].strip(" "))
    elif cmd == "serialReadLine":
        print "serial read:"
        response = ser.readline()
        print response
        conn.sendall(response)
        print "read done"

    return

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'
s.bind((HOST,PORT))
print 'Socket bind complete'

s.listen(10)    #parameter: backlog, controls number of connections that are 'queued'
print 'Socket now listening'

#Function f or handling connections. this will be used to create threads
def clientthread(conn):
    #sending message to connected client        
    try:
        while True:
            data = conn.recv(1024)
            if not data:
                break
            processData( data )

        #out of the loop
        conn.close()
    except socket.error , msg:
        print 'Recv failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]

while 1:
    #wait to accept a connection - blocking call
    conn, addr = s.accept()
    print 'Connected with ' + addr[0] + ':' + str(addr[1])

    #start new thread takes 1st argument as a function name to be run
    #second is the tuple of arguments to the function
    start_new_thread(clientthread,(conn,))

s.close

the most important parts of that being:

    ser = Serial('/dev/ttyAMA0', baudRate, timeout=timeOut)

and the serial config/read/write areas of the el/if block

and the second sever (that is not working):

import socket
import sys
from time import sleep
from serial import Serial
from thread import *
import binascii

#HOST = ' ' # Symbolic name meaning all available interfaces
HOST = '10.1.10.28'
PORT = 8889 # Arbitrary non-privleged port


s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'

try:
    s.bind((HOST,PORT))
except socket.error , msg:
    print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]
    sys.exit()

print 'Socket bind complete'

s.listen(10)    #parameter: backlog, controls number of connections that are 'queued'
print 'Socket now listening'

ser = Serial('/dev/ttyAMA0', baudrate = 115200, timeout= 10)
#ser.open #--- uncommenting this does not make a difference 

#Function f or handling connections. this will be used to create threads
def clientthread(conn):

    #infinite loop so the function does not terminate and thread does not end
    try:
        while True:
            print  "step 1"
            first = conn.recv(1)
            print  "step 2"
            if not first:
                break
            hextFirst = hex( ord(first) )
            print hextFirst
            if hextFirst == '0xff':
                print  "step 3"
                #ser.write(hextFirst)           #send 0xff (converted)
                ser.write(first)                #send 0xff (orignal)

                length = conn.recv(1)               #get length
                hextLength = hex( ord(length) )     #convert length
                intlength = ord(length)
                print "hextLength: " + hextLength
                print "step 4"
                #ser.write(hextLength)          #send length (converted)
                ser.write(length)               #send length (original)
                cmd = 0
                if ord(length) == 0:
                    cmd = conn.recv(13)
                else:
                    cmd = conn.recv(ord(length)-2)

                hextCmd = binascii.b2a_hex(cmd)

                print cmd
                print "hextCmd: " + hextCmd
                #ser.write(hextCmd)         #send cmd (converted)
                ser.write(cmd)              #send cmd (original)

                #sleep(1)
                response = ser.read(1)          #get response
                #hextResponse = hex(ord(response))

                print "serial resp: " + response
                conn.sendall(response)          #send response to LV
                print "step 5"
            print "step 6"
            sleep(10)

        #out of the loop
        conn.close()
    except socket.error , msg:
        print 'Recv failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]

try:
    while 1:
        #wait to accept a connection - blocking call
        conn, addr = s.accept()
        print 'Connected with ' + addr[0] + ':' + str(addr[1])

        #start new thread takes 1st argument as a function name to be run
        #second is the tuple of arguments to the function
        start_new_thread(clientthread,(conn,))

    s.close
except KeyboardInterrupt:
    ser.close
    s.close
    print "Exiting: Keyboard Interrupt"

I realize that is alot of code to go through, but you can ignore most of it, i'm just wondering what went wrong in the serial config/write. Like i said initially, the problem comes from the logic analyzer not seeing any serial communications (to or from) on the 2nd server, while the first server is working just fine

Answer 1

Try releasing /dev/ttyAMA0 from the default console by editing /boot/cmdline.txt

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 ..

change it to

dwc_otg.lpm_enable=0 console=tty1 .....

and removing this line from /etc/inittab

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

also make sure you run the program as super user sudo