433Mhz Test

Fleeting

Table of Contents

using raspberry pi -> does not work
using arduino uno r3 -> does not work
- try reading the values using an analog pin
using a couple of esp32 -> does not work
trying with the rfm69hcw by adafruit, using circuitpython -> WORKS !
Notes linking here
Permalink

433Mhz test FS1000A and mx-rm-5v

https://www.gotronic.fr/art-kit-emetteur-recepteur-433-mhz-txrx433-36883.htm

using raspberry pi -> does not work

trying https://www.instructables.com/Super-Simple-Raspberry-Pi-433MHz-Home-Automation/

I plugged the receiver on the GPIO 4 and the transmitter on the GPIO 17.

Using the given code, adjusted to my pins.

from datetime import datetime
import RPi.GPIO as GPIO
from collections import Counter
MAX_DURATION = 10
RECEIVE_PIN = 4

def capture():
    global RECEIVED_SIGNAL
    RECEIVED_SIGNAL = [[], []] # [[time of reading], [signal reading]]
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(RECEIVE_PIN, GPIO.IN)
    cumulative_time = 0
    beginning_time = datetime.now()
    print('**Started recording**')
    while cumulative_time < MAX_DURATION:
        time_delta = datetime.now() - beginning_time
        RECEIVED_SIGNAL[0].append(time_delta)
        RECEIVED_SIGNAL[1].append(GPIO.input(RECEIVE_PIN))
        cumulative_time = time_delta.seconds
        print('**Ended recording**')
        print(len(RECEIVED_SIGNAL[0]), 'samples recorded')
        GPIO.cleanup()
        print('**Processing results**')
    for i in range(len(RECEIVED_SIGNAL[0])):
        RECEIVED_SIGNAL[0][i] = RECEIVED_SIGNAL[0][i].seconds + RECEIVED_SIGNAL[0][i].microseconds/1000000.0
        print(f"Received: {Counter(RECEIVED_SIGNAL[1])}")

def dump(path="data/a.csv"):
    Path(path).write_text("".join(f"{a},{b}\n" for a, b in zip(*RECEIVED_SIGNAL)))

def plot():
    import matplotlib.pyplot as pyplot
    print '**Plotting results**'
    pyplot.plot(RECEIVED_SIGNAL[0], RECEIVED_SIGNAL[1])
    pyplot.axis([0, MAX_DURATION, -1, 2])
    pyplot.show()

def main():
    capture()
    plot()

if __name__ == "__main__":
    main()

trying without doing anything with my devices

I already get a lot of data.

There are maybe some devices that send those data and that I don’t know about.

trying a base scenario without anything

I try unplugging the receiver.

trying with another library

https://www.instructables.com/RF-433-MHZ-Raspberry-Pi/

using arduino uno r3 -> does not work

see,
- trying to run a program on arduino without the IDE,

Let’s try to follow the example shown in https://www.instructables.com/Arduino-433Mhz-Wireless-Communication-Rc-Switch/.

This is the wiring:

arduino-cli lib search rcswitch

arduino-cli lib install rc-switch

Downloading rc-switch@2.6.4...

rc-switch@2.6.4 0 B / 20.47 KiB    0.00%
rc-switch@2.6.4 downloaded
Installing rc-switch@2.6.4...
Installed rc-switch@2.6.4

See the examples in https://github.com/sui77/rc-switch/tree/master/examples

Here, let’s use the code from https://github.com/sui77/rc-switch/blob/master/examples/ReceiveDemo_Simple/ReceiveDemo_Simple.ino

#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

void setup() {
  Serial.begin(9600);
  Serial.print("Setting up");
  mySwitch.enableReceive(0);  // Receiver on interrupt 0 => that is pin #2
}

void loop() {

  if (mySwitch.available()) {

    Serial.print("Received ");
    Serial.print( mySwitch.getReceivedValue() );
    Serial.print(" / ");
    Serial.print( mySwitch.getReceivedBitlength() );
    Serial.print("bit ");
    Serial.print("Protocol: ");
    Serial.println( mySwitch.getReceivedProtocol() );

    mySwitch.resetAvailable();
  }
}

Sketch uses 3114 bytes (9%) of program storage space. Maximum is 32256 bytes.
Global variables use 401 bytes (19%) of dynamic memory, leaving 1647 bytes for local variables. Maximum is 2048 bytes.

[92mUsed library[0m [92mVersion[0m [90mPath[0m
[93mrc-switch[0m    2.6.4   [90m/home/sam/Arduino/libraries/rc-switch[0m

[92mUsed platform[0m [92mVersion[0m [90mPath[0m
[93marduino:avr[0m   1.8.6   [90m/home/sam/.arduino15/packages/arduino/hardware/avr/1.8.6[0m
New upload port: /dev/ttyACM1 (serial)

I have a DI-O chacon shutter remote that I can use to check my setup.

arduino-cli monitor --timestamp --quiet -p "${device}" -b arduino:avr:uno

[2024-12-20 13:29:44] Setting up

I point a remote control to the device and click on a button and… nothing happens.

Hmmm, let’s try to dig into what it does.

The code of rc-switch uses attachInterrupt(), so let’s try to use it.

#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

volatile byte state = LOW;

void handleInterrupt() {
  state = !state;
  if(state){
    Serial.println("1");
  } else {
    Serial.println("0");
  }
}

void setup() {
  Serial.begin(9600);
  Serial.print("Setting up");
  attachInterrupt(digitalPinToInterrupt(2), handleInterrupt, CHANGE);
}

void loop() {
}

Sketch uses 1920 bytes (5%) of program storage space. Maximum is 32256 bytes.
Global variables use 232 bytes (11%) of dynamic memory, leaving 1816 bytes for local variables. Maximum is 2048 bytes.

[92mUsed library[0m [92mVersion[0m [90mPath[0m
[93mrc-switch[0m    2.6.4   [90m/home/sam/Arduino/libraries/rc-switch[0m

[92mUsed platform[0m [92mVersion[0m [90mPath[0m
[93marduino:avr[0m   1.8.6   [90m/home/sam/.arduino15/packages/arduino/hardware/avr/1.8.6[0m
New upload port: /dev/ttyACM1 (serial)

Monitoring the board, I can see a lot of things going on.

: [2024-12-20 Fri 13:59] 1

[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1
[2024-12-20 13:59:07] 0
[2024-12-20 13:59:07] 1

I realized then that this happens:

no wire connected to the pin: steady value
connecting the wire: going crazy
shorting the pin with 5V: steady 1
shorting the pin with GND: steady 0
connecting to the data of the receiver: going crazy

I don’t understand all those changes, let’s try to see how the other interrupts behave.

#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

volatile byte state = LOW;

void handleInterruptRising() {
  Serial.println("Rising");
}

void handleInterruptFalling() {
  Serial.println("Falling");
}

void handleInterruptChange() {
  Serial.println("Change");
}

void handleInterruptLow() {
  Serial.println("Low");
}

void setup() {
  Serial.begin(9600);
  Serial.print("Setting up");
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), handleInterruptRising, RISING);
  attachInterrupt(digitalPinToInterrupt(2), handleInterruptFalling, FALLING);
  attachInterrupt(digitalPinToInterrupt(2), handleInterruptLow, LOW);
  attachInterrupt(digitalPinToInterrupt(2), handleInterruptChange, CHANGE);
}

void loop() {
}

Sketch uses 2018 bytes (6%) of program storage space. Maximum is 32256 bytes.
Global variables use 236 bytes (11%) of dynamic memory, leaving 1812 bytes for local variables. Maximum is 2048 bytes.

[92mUsed library[0m [92mVersion[0m [90mPath[0m
[93mrc-switch[0m    2.6.4   [90m/home/sam/Arduino/libraries/rc-switch[0m

[92mUsed platform[0m [92mVersion[0m [90mPath[0m
[93marduino:avr[0m   1.8.6   [90m/home/sam/.arduino15/packages/arduino/hardware/avr/1.8.6[0m
New upload port: /dev/ttyACM1 (serial)

[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change
[2024-12-20 14:07:31] Change

It looks like I can only see the last ICR code, while the documentation says that they would be chained. Switching the “Change” and “Low” lines in the code will result in a lot of “Low” lines in the output.

I appears clearly to me that I don’t understand at all how arduino interruption works.

try reading the values using an analog pin

I plugged the data pin of the receiver on A0 and ran this code.

#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

void setup() {
  Serial.begin(9600);
}

void loop() {
  float val = analogRead(0);
  Serial.println(val);
  delay(10); // ms
}

Sketch uses 3504 bytes (10%) of program storage space. Maximum is 32256 bytes.
Global variables use 239 bytes (11%) of dynamic memory, leaving 1809 bytes for local variables. Maximum is 2048 bytes.

[92mUsed library[0m [92mVersion[0m [90mPath[0m
[93mrc-switch[0m    2.6.4   [90m/home/sam/Arduino/libraries/rc-switch[0m

[92mUsed platform[0m [92mVersion[0m [90mPath[0m
[93marduino:avr[0m   1.8.6   [90m/home/sam/.arduino15/packages/arduino/hardware/avr/1.8.6[0m
New upload port: /dev/ttyACM1 (serial)

I ran the program and pressed 3 times the shutter close button, then 3 times the shutter open button and 3 times again the shutter close button.

Zooming a bit, I can see this pattern.

Now, let’s try to disconnect the receiver, keeping the wire dangling.

And after removing the wire.

Ok, I definitely got lost. Either my arduino board is broken, or I missed something that will retrospectively appear obvious.

using a couple of esp32 -> does not work

https://techtotinker.com/2021/09/046-micropython-technotes-rf433-transceivers/

Still nothing, putting the data pin to high and low every 3 seconds on the emitter and scanning the receiver every second, I can see nothing.

I think I tried with all combinations of my 5 transmitters X 5 receivers.

This video suggests that they are in fact quite bad.

I also soldered 17cm wires as antennas, without more luck so far.

trying with the rfm69hcw by adafruit, using circuitpython -> WORKS !

https://learn.adafruit.com/radio-featherwing/circuitpython-for-rfm69

https://docs.circuitpython.org/projects/rfm69/en/latest/examples.html

install the dependencies

on a real board
1. download the bundle from https://github.com/adafruit/Adafruit_CircuitPython_Bundle/releases
2. extract and copy adafruit_bus_device and adafruit_rfm69.py into media…/CIRCUITPY/lib
on the ft232h
1. pip install adafruit-circuitpython-rfm69 (or download the bundle like above)

initialize the communication.

import adafruit_rfm69
import board
import busio
import digitalio

RADIO_FREQ_MHZ = 433.0

setup the pins depending on the board

on the pico w

CS = digitalio.DigitalInOut(board.GP0)
RESET = digitalio.DigitalInOut(board.GP1)
spi = busio.SPI(board.GP2, MOSI=board.GP3, MISO=board.GP4)

on the Adafruit Feather HUZZAH with RP2040

CS = digitalio.DigitalInOut(board.D5)
RESET = digitalio.DigitalInOut(board.D6)
spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)

on the ft232h

CS = digitalio.DigitalInOut(board.D5)
RESET = digitalio.DigitalInOut(board.D6)
spi = board.SPI()

setup the rfm69 object

rfm69 = adafruit_rfm69.RFM69(spi, CS, RESET, RADIO_FREQ_MHZ, baudrate=1000000)

send data

import time
while True:
    print("sending")
    rfm69.send(bytes("Hello world!\r\n", "utf-8"))
    time.sleep(1)

receive data

while True:
    packet = rfm69.receive(timeout=2)
    if packet is None:
        print("Received nothing! Listening again...")
    else:
        print(f"Received (raw bytes): {packet}")
        packet_text = str(packet, "ascii")
        print(f"Received (ASCII): {packet_text}")

what I learned

I needed a lot of trials and error to get the correct wiring. I realize how important it was to use the voltmeter and check every pin, using the code to toggle on and off and see whether the expected 3.3 output is actually there.

I thought that antennas were needed only when separating the devices, but even at 5cm, I often got nothing until I simply put a wire on the antenna hole.

Notes linking here

playing with circuitpython in circuit playground express