Reading a FlySky FS-i6x joystick

The RC signal is read from specific pins on a microcontroller, and the code then outputs the duty cycle value of the signal. We’ll first learn how to read our x2 joystick values.

• Our joystick consists of x2 linear potentiometers
  • one for the X axis, channel 1
  • one for the y axis, channel 2
• We also have access to 2 more channels on 3/4 that are joysticks, but we won’t use them for this course.

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Download the py file

"""Basic RC Analog input Control
Outputs an analog channel duty cycle rating in 0>100.
50 is the deadpoint. 0 is miniumum, 100 is maximum.

"""

import time
import board
from rc import RCReceiver

rc = RCReceiver(ch1=board.D10, ch2=board.D11, ch3=None, ch4=None, ch5=board.D12, ch6=board.D13)

# Main code
while True:
    # Read channels
    channel_1 = rc.read_channel(1)
    channel_2 = rc.read_channel(2)
    if channel_1 is not None and channel_2 is not None: # must not be None to do something with the output
        print("1: ", channel_1, "2: ", channel_2)
    
    rc.ensure_cycle()  # Maintains sync with our 20ms cycle every loop iteration

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Code Breakdown

Libraries

"""
Basic RC Analog input Control
Outputs an analog channel duty cycle rating in 0 > 100.
50 is the deadpoint. 0 is miniumum, 100 is maximum.
"""
import time
import board
from rc import RCReceiver

• import time: Imports the time module, which allows us to work with time-related functions, such as delays.
• import board: Imports the board module, which maps the microcontroller’s pins.
• from rc import RCReceiver: Imports the RCReceiver class from the rc module, allowing us to create an RC receiver object.

Initializing the RCReceiver instance

The next section of the code initializes the RC receiver channels.

rc = RCReceiver(ch1=board.D10, ch2=board.D11, ch3=None, ch4=None, ch5=board.D12, ch6=board.D13)

• rc: This is an instance of the RCReceiver class, which we will use to read the values from the RC receiver.
• Channels: ch1 to ch6 represent the input channels from the RC receiver. They are connected to specific pins (e.g., board.D10, board.D11, etc.).
  • Note, we ignore Channels 3/4, so we assign them a value of None so that the library will ignore these channels.

Main Code Loop

This is the main part of our script where we continuously read and print the values from the RC receiver.

# Main code
while True:
    # Read channels
    channel_1 = rc.read_channel(1)
    channel_2 = rc.read_channel(2)
    if channel_1 is not None and channel_2 is not None: # must not be None to do something with the output
        print("1: ", channel_1, "2: ", channel_2)
    rc.ensure_cycle()  # Maintains sync with our 20ms cycle every loop iteration

• Reading Channels:
  • channel_1 = rc.read_channel(1): Reads the value from channel 1 (and 2 respectively)
  • This will return a value between 0-100:
  • If joystick is in the middle: 50
  • If the Joystick Channel 1 Left, or Channel 2 down: 0
  • If the Joystick Channel 1 Right or Channel 2 Up: 100
• Check for None:
  • if channel_1 is not None and channel_2 is not None: Ensures that both channels have valid readings before proceeding. If there is ever an error in reading a channel, the method will return None.
• Delay:
  • rc.ensure_cycle() : maintains correct sync for cycle readings of our rc reciever (20 milliseconds). This matches the length of a single duty cycle of the RC receiver, ensuring the code reads the next cycle’s data.
  • We always have to ensure sync at the end of our while True: loop in order to keep our readings in sync with our duty cycle.

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