Rpi based quadcopter with 2.4 radio control

Woow, that's way more than I've expected, thank you so much :)
Apparently forum has messed up my link - here is correct one. As you predicted Rx voltage is between 4V and 6V so I must lower voltage(and buy 2 converters, because it has 4ch).
It is good news anyway because now I think that I don't need to hesitate buying this controller :)

Altough, during research in the internet I've found little bit different approach - connecting radio receiver to rPi using Arduino micro trough the I2C. That's because raspberryPi isn't accurate enough to precise read joystick values(freeing Rpis resources a little bit is another thing).
Altough, another device like Arduino consume more power, which is very limited on flying vehicle...
What do you think, which approach would give better results?

Thank you again for this awesome support!

P.S. I'm starting to understand why quadcopters are so expensive... ;)

Hello,
I've received my transmitter and receiver. Receiver needs 5-6V to power but when I measured voltage on signal pin multimeter shows voltage between 0.22V and 0.49V... I know that it is probably stupid question but it really can be this low and I don't need this level shifter or I cannot measure PWM voltage just by multimeter? :-) I would be very glad if you could help me to understand that :-)
Thank you in advance!

Well, I've obviously had some lack of fundamentals... ;) Thank you very much, that cleared up a lot for me! :)

I've succeed to connect all stuff to Pi, pigpio library is reading rising and falling edges, but - I cannot notice any change of PWM signal while moving joystick in transmitter.

Could you please be so awesome to look at that code and give me some hint is it correct? :)

#!/usr/bin/python
import pigpio
import time

pi = pigpio.pi()

#defining variables to avoid errors with math at start

rising = 0
falling = 0
lowTime = 0

#infinite while loop to catch PWM signal and count duty cycle

while(1):
    if pi.wait_for_edge(25):
        rising = time.time()
        if falling != 0:
            lowTime = rising-falling
    
    if pi.wait_for_edge(25, pigpio.FALLING_EDGE, 5.0):
        falling = time.time()
        highTime = falling-rising
    dutyIn = highTime / (highTime + lowTime)
    print dutyIn
#    dutyOut = int(dutyIn * 255)
#    if dutyOut < 121 or dutyOut > 129:
#        print dutyOut

It all the times gives me value about 0.496645195921
or value about 125 after convert to dutyOut (it fluctuates a little all the time).

Thank you very very much in advance! :)

Ok, so I ran your code and now the question is how approximately is approximately ;)
this is sample output when joystick is idle:

0.501410775858
0.0522830486298
0.0519888401031
0.104271888733
---
0.500401716425
0.0522699356079
0.0521860122681
0.104455947876
---
0.501489845079
0.052365064621
0.0520539283752
0.104418992996
---
0.49917093002
0.0521080493927
0.0522811412811
0.104389190674
---
0.500952096907
0.0520598888397
0.0518620014191
0.103921890259
---
0.499612396896
0.0520901679993
0.0521709918976
0.104261159897
---
0.500820220919
0.0518980026245
0.0517280101776
0.103626012802
---
0.497994095311
0.0519990921021
0.0524179935455
0.104417085648
---

and here is the output when joystick is moved to another position:

0.500880177312
0.0523710250854
0.0521869659424
0.104557991028
---
0.502921860706
0.0526921749115
0.0520799160004
0.104772090912
---
0.500981718225
0.0520129203796
0.0518090724945
0.103821992874
---
0.497412664579
0.0519089698792
0.0524489879608
0.10435795784
---
0.500351619056
0.0519080162048
0.0518350601196
0.103743076324
---

So the high time + low time is more or less the same, but maybe this difference is too big anyway?

I've checked on multimeter and there I can see the difference when moving josticks. The only thing that looks weird to me(but again - it may be again just my lack of fundamental knowledge in some parts ;) ) that before the level shifter multimeter shows between 0.22V and 0.49V and after the converter it shows between 1.40V and 1.60V. But anyway, at least I know that level shifter works and Pi should obtain some information about signal change...

Thank you again for you help!
Cheers.

Sure, below you can find photos, I hope you can see what you want.

Receiver:

I've connected external power source from 4x AA rechargable batteries(5V output from Pi causes freezing, so I must provide it other way) - pin 2 and 3 on 1st channel.
Signal pins from 1-6 - first pin of every channel.

Level shifter:

- VCCB and GND - positive and negative from receiver's power source
- B1 to B6 - signal pins from receiver
- VCCA 3.3V output power from Pi
- according to converter's documentation OE should stay low to enable output
- A1-A6 connections to GPIO pins on Pi(currently only 1st and 5th)

Accelerometer and altitude meter are connected trough I2C to SDA, SCL and Pi 3.3v power so it shouldn't interfere anything, it was easier for me to connect all wiring at once :)

I am really corious what I've made wrong that it works like that... But other parts for quadcopter are still in shipping so at least I'm not so frustrated that I've stucked :P

Hi,

I also thought that it was it but unfortunately it didn't change anything, still the same values without any changes. I don't know, maybe Pi is too slow to get PWM like that?

Sure! I am really really grateful and so pleasantly surprised that you are so involved in this mine problem. Thanks again! :-) meanwhile I will try the @Ginger suggestion, I will let you know if I will figure out something eventually :-)

Hi!
Well, you are wiser than me, cause you are making better research first. Unfortunately PCA9685 is only OUTPUT device :( You can check my question directly at adafruit's forum. You can use it to send PWM signal to ESCs(and as far I discovered it is quite recommended that way) but you cannot use it to get signal from transmitter. The only solution that was left for me is a simple Arduino mini(could be cheap one from ebay) but unfortunately I don't have any time to work further on my project, it is still in parts ;)
But I have built quadcopter on built flight controller(first KK2.1.5, now Naza M Lite) and I must say - it is good to start with that to get familiar with multicopter way of working/flying. KK2.1.5 is quite cheap and you can understand how all of it works(especially PIDs, motors and propellers setup etc) :) I don't thing that I could made my own made quadcopter flight without any of this knowledge ;)
I would be glad if you could let me know when you will solve the transmitter input case :)
Cheers!