PySerial, Python, Raspberry Pi and issuing AT commands to a Mobile Dongle

For anyone who saw my last post, they will know that I've been working on a number of projects - the current one is to do with the RP and texting.

I couldn't find any modules out there that I liked to talk to the dongle, so I decided to make my own functions to do the job. It's not perfect, but it's doing the job for me and will be expanded on over time.

See below:

You'll need PySerial for this to work, and also create a serial object called 'dongle'
example: dongle = serial.Serial(port="/dev/ttyUSB0",baudrate=115200,timeout=2,rtscts=0,xonxoff=0)

# write a command to the dongle, check the line out buffer for the correct response and return it
# cmd is the command we issue
# success is what we're looking for in the buffer if it was successful
# fail is what we're looking for if it fails
# AT is whether we put the "AT+" in front of the command
# if we pass "pass" as the cmd, then we don't write anything - useful if we're looking for 2 outputs from a command (such as +CMGS and OK when we send a message)

def WriteBuffer(cmd, Success, Fail, AT):
if (cmd == "pass"):
pass
elif (AT == "Y"):
dongle.write('AT'+cmd+'\r')
elif (AT == "N"):
dongle.write(cmd+'\r')
Found = "False"
BufferCounter = 0
while (Found == "False"):
Buffer = dongle.readline()
if Buffer.find(Fail) > -1:
return Fail
if Buffer.find(Success) > -1:
if (Success == "+CMGW:"):
SuccessValue = Buffer.split(": ")
Success = SuccessValue[1]
if (Success == "+CMGR:"):
Next = dongle.readline()
SuccessValue = str(Buffer)+","+str(Next)
Success = SuccessValue
Next = dongle.readline()
Next = dongle.readline()
if (Success == "+CSQ:"):
SuccessValue = Buffer.split(": ")
Success = SuccessValue[1]
Next = dongle.readline()
Next = dongle.readline()
if (Success == "+CBC:"):
SuccessValue = Buffer.split(": ")
Success = SuccessValue[1]
Next = dongle.readline()
Next = dongle.readline()
if (Success == "+CPAS:"):
SuccessValue = Buffer.split(": ")
Success = SuccessValue[1]
Next = dongle.readline()
Next = dongle.readline()
return Success
if BufferCounter > 5:
return "timeout"
BufferCounter = BufferCounter + 1

Function to send a text below - you can add captures for errors that are thrown back:

# sendnumber = mobile, message = the message we want to send

def SendText(SendNumber, SendMessage):
WriteBuffer(('+CMGS="%s"') % SendNumber, ">", "Error", "Y")
WriteBuffer(SendMessage, ">", "Error", "N")
WriteBuffer(chr(26), "+CMGS:", "Error", "N")
WriteBuffer("pass", "OK", "Error", "N")

As I said, it's not perfect, but it does allow you to issues commands and get back the output quite easily.