Question

I am pretty new to python and working with firmata I am trying to play around with an arduino .

Here is what I want to happen:

• Set arduino up with an LED as a
  digital out

• Set potentiometer to analog 0

• Set PyQt timer up to update
  potentiometer position in
  application

• Set a threshold in PyQt to turn
  LED on (Analog in has 1024bit
  resolution, so say 800 as the
  threshold)

I am using this firmata library : Link

Here is the code that I am having trouble with:

import sys
from PyQt4 import QtCore, QtGui
from firmata import *

 # Arduino setup
 self.a = Arduino('COM3')
 self.a.pin_mode(13, firmata.OUTPUT)

 # Create timer
    self.appTimer = QtCore.QTimer(self)

    self.appTimer.start(100)
    self.appTimer.event(self.updateAppTimer())


def updateAppTimer(self):
    self.analogPosition = self.a.analog_read(self, 0)
    self.ui.lblPositionValue.setNum()

I am getting the error message:

Traceback (most recent call last):
File “D:\Programming\Eclipse\IO Demo\src\control.py”, line 138, in
myapp = MainWindow()
File “D:\Programming\Eclipse\IO Demo\src\control.py”, line 56, in init
self.appTimer.event(self.updateAppTimer())
File “D:\Programming\Eclipse\IO Demo\src\control.py”, line 60, in updateAppTimer
self.analogPosition = self.a.analog_read(self, 0)
TypeError: analog_read() takes exactly 2 arguments (3 given)

If I take ‘self’ out I get the same error message but that only 1 argument is given

What is python doing implicitly that I am not aware of?

Blockquote

Answer 1

In your code ‘a’ is the class instance, so all methods, bound to it, already have self pointers passed as first params.
Welcome to python, someday you’d like it 🙂

In contra, you can call any method as unbound (and I’m sure you do it in every constructor of any derived class). Syntax is:

instance = Type()
#bound method.
instance.methodName(params)

#unbound method call, 'instance' is the instance of some object, pointer to witch
#you want to pass to method. These calls are similar.
Type.methodName(instance, params)