Computing stuff tied to the physical world

Meet the RF Node Watcher

All of the tinkering so far is nice, but let’s raise the stakes a bit and create a little setup to test all this, so we can end up with this funny geeky gadget called the RF Node Watcher:

DSC 5184

That’s the main µC board, an RFM69 radio for the 868 MHz ISM band (connected over SPI), a push button, and a fun little 128×64 OLED graphics display (connected over I2C).

The back side has a bit of wiring soldered on to connect it all together:

DSC 5217

Here’s a demo of the OLED in action (full code in the Embello repository on GitHub):

    #include <SPI.h>
    #include <Wire.h>
    #include <Adafruit_GFX.h>
    #include <Adafruit_SSD1306.h>

    Adafruit_SSD1306 oled;

    static const uint8_t logo_64x64[] = { ... };

    void setup()   {                
        // generate OLED supply internally from 3.3V
        oled.begin(SSD1306_SWITCHCAPVCC, 0x3C);

        oled.drawBitmap(32, 00,  logo_64x64, 64, 64, 1);

    void loop() {}

As you can see, it uses an existing library to drive the OLED. Here is the result:

IMG 0197

Running a little demo for the RFM69 wireless radio is deceptively simple, because most of the hard work has already been done, and this code was simply ported from the LPC8xx:

    #include <SPI.h>
    #include "spi.h"
    #include "rf69.h"

    RF69<SpiDev> rf;

    void setup () {

        rf.init(1, 42, 8686);

    void loop () {
        uint8_t buffer [70];
        int n = rf.receive(buffer, sizeof buffer);
        if (n >= 0) {
            Serial.print("got #");
            for (int i = 0; i < n; ++i) {
                Serial.print(' ');

The output is reported over the USB serial port.

And as final “pièce de résistance” for now, there’s a sketch called watcher, which combines everything into one big demo, using the components on this board. It listens for incoming packets and shows the last four of them in a tiny compact list on that OLED display:

IMG 0198

Only useful for geeks who need to “see” all those packets flying through the air, but hey!

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