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6.4 Using an Infrared Remote Control

In this lesson, we’ll learn how to use an infrared (IR) remote control and an IR receiver module with the Raspberry Pi Pico 2. This will allow us to receive and decode signals from an IR remote, enabling us to control our projects wirelessly.

What You’ll Need

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Newton Lab Kit	450+	Newton Lab Kit

You can also buy them separately from the links below.

SN	COMPONENT	QUANTITY	LINK
1	Raspberry Pi Pico 2	1	BUY
2	Micro USB Cable	1
3	Breadboard	1	BUY
4	Jumper Wires	Several	BUY
5	Infrared Receiver	1	BUY

Understanding Infrared Communication

Infrared communication involves transmitting data wirelessly using infrared light. Common household devices like TVs and DVD players use IR remote controls for operation.

IR Transmitter (Remote Control): Emits modulated infrared light when a button is pressed.
IR Receiver Module: Detects the modulated IR light and converts it into electrical signals that can be decoded.

Circuit Diagram

sch_irrecv

Wiring Diagram

wiring_irrecv

Writing the Code

Let’s write a MicroPython script to receive and decode IR signals from the remote control.

Note

Open the 6.4_ir_remote_control.py from newton-lab-kit/micropython or copy the code into Thonny, then click “Run” or press F5.
Ensure the correct interpreter is selected: MicroPython (Raspberry Pi Pico).COMxx.
Here you need to use the libraries in ir_rx folder, please check if it has been uploaded to Pico, for a detailed tutorial refer to Upload the Libraries to Pico.

import time
from machine import Pin
from ir_rx.nec import NEC_8  # Adjust based on your remote's protocol
from ir_rx.print_error import print_error

# Initialize the IR receiver pin
ir_pin = Pin(17, Pin.IN)

# Callback function to handle received data
def ir_callback(data, addr, ctrl):
    if data < 0:  # Repeat code or error
        pass
    else:
        key = decode_key(data)
        print("Received Key:", key)

# Function to decode the received data into key presses
def decode_key(data):
    key_codes = {
        0x45: "POWER",
        0x46: "MODE",
        0x47: "MUTE",
        0x44: "PLAY/PAUSE",
        0x40: "BACKWARD",
        0x43: "FORWARD",
        0x07: "EQ",
        0x15: "-",
        0x09: "+",
        0xD: "U/SD",
        0x16: "0",
        0x19: "cycle",
        0xC: "1",
        0x5E: "3",
        0x18: "2",
        0x8: "4",
        0x1C: "5",
        0x5A: "6",
        0x42: "7",
        0x52: "8",
        0x4A: "9",
        0x0: "ERROR",
        # Add more key codes based on your remote
    }
    return key_codes.get(data, "UNKNOWN")

# Instantiate the IR receiver
ir = NEC_8(ir_pin, ir_callback)
ir.error_function(print_error)  # Optional: to print errors

try:
    while True:
        time.sleep(1)  # Keep the main thread alive
except KeyboardInterrupt:
    ir.close()
    print("Program terminated")

When you run this code and press buttons on your infrared remote control, the Thonny Shell (or any other serial monitor) will display the name of the key you pressed. For example, if you press the “PLAY” button on the remote, the Shell will show “Received Key: PLAY”.

Understanding the Code

Import Modules:
- ir_rx.nec.NEC_8: The NEC protocol decoder for 8-bit addresses.
- print_error: Function to print error messages.
```
import time
from machine import Pin
from ir_rx.nec import NEC_8
from ir_rx.print_error import print_error
```
Initialize IR Receiver Pin:
```
ir_pin = Pin(17, Pin.IN)
```

Define Callback Function:

This function is called automatically when data is received. The data parameter contains the key code.

def ir_callback(data, addr, ctrl):
    if data < 0:
        pass  # Ignore repeat codes
    else:
        key = decode_key(data)
        print("Received Key:", key)

Decode Key Function:

Maps received key codes to human-readable labels.

def decode_key(data):
    key_codes = {
    0x45: "POWER",
    0x46: "MODE",
    0x47: "MUTE",
    0x44: "PLAY/PAUSE",
    0x40: "BACKWARD",
    0x43: "FORWARD",
    0x07: "EQ",
    0x15: "-",
    0x09: "+",
    0xD: "U/SD",
    0x16: "0",
    0x19: "cycle",
    0xC: "1",
    0x5E: "3",
    0x18: "2",
    0x8: "4",
    0x1C: "5",
    0x5A: "6",
    0x42: "7",
    0x52: "8",
    0x4A: "9",
    0x0: "ERROR",
    # Add more key codes based on your remote
    }
    return key_codes.get(data, "UNKNOWN")

Instantiate IR Receiver:

Sets up the IR receiver with the callback function.
```
ir = NEC_8(ir_pin, ir_callback)
ir.error_function(print_error)
```

Main Loop:

Keeps the program running to listen for IR signals. Gracefully handles program termination.

try:
    while True:
        time.sleep(1)
except KeyboardInterrupt:
    ir.close()
    print("Program terminated")

Applications

Control Projects Wirelessly: Use the IR remote to control LEDs, motors, or other peripherals.
Build a Universal Remote Decoder: Expand the code to handle multiple protocols or remotes.

Conclusion

In this lesson, you’ve learned how to use an IR receiver with the Raspberry Pi Pico 2 to decode signals from an infrared remote control. This enables you to add wireless control to your projects using common household remotes.

Callback Function - Wikipedia