ESP32-S3 board
The brain that runs your uploaded sketch.
01 First, know the pieces
What you need
Six things, most of them small. Tap Define on any part you haven't met — the answer opens as a field note you can read and dismiss without losing your place.
GPIO extension board
Spreads the pins into rows you can reach and label.
RGB LED
Three lights — red, green, blue — in one dome with a shared pin.
3 × 220 Ω resistors
One in series with each colour leg to keep the current gentle.
Jumper wires
Temporary, solder-free connections.
Arduino IDE
Uploads the sketch to the board.
02 Make the physical circuit
Chart the circuit
The official Freenove diagram is your chart — schematic on top, the same circuit built on a breadboard below. Click it to enlarge. Each connection tells you where the wire goes and why.
Red leg (via 220 Ω)
→GPIO 38
One PWM channel sets how much red shows.
Green leg (via 220 Ω)
→GPIO 39
One PWM channel sets how much green shows.
Blue leg (via 220 Ω)
→GPIO 40
One PWM channel sets how much blue shows.
Common (long) pin
→3.3V
All three share this positive pin so a colour lights when its pin goes LOW.
The common pin goes to 3.3V. This is a common-anode LED, so the long common pin goes to 3.3V and not to ground — the opposite of a single LED. Each colour leg reaches its own GPIO through a 220 Ω resistor. Unplug USB before you move any wire.
03 One action at a time
Build it
This is the main path — you can finish the day without opening a single field note. Tap each step as you go to keep your place.
0 / 9 done
Seat the ESP32-S3 on the GPIO extension board and keep USB unplugged while you wire.
Find the RGB LED's long pin — that's the common one shared by all three colours.
Wire the red leg through a 220 Ω resistor to GPIO 38.
Wire the green leg through a 220 Ω resistor to GPIO 39.
Wire the blue leg through a 220 Ω resistor to GPIO 40.
Run the long common pin to 3.3V, not to ground.
Compare every wire to the chart before you plug in USB.
Open
Sketch_05.1_RandomColorLight.inoin Arduino IDE and upload it.Watch the dome change colour again and again.
04 Read just enough code
Read the code
The sketch sets up three PWM channels, then paints a colour by giving each one a brightness. Switch to MicroPython if you'd rather see the same idea in Python — the wiring never changes.
const byte ledPins[] = {38, 39, 40}; // R, G, B
const byte chns[] = {0, 1, 2};
void setup() {
for (int i = 0; i < 3; i++) {
ledcAttachChannel(ledPins[i], 1000, 8, chns[i]);
}
}
void loop() {
int red = random(0, 256);
int green = random(0, 256);
int blue = random(0, 256);
ledcWrite(ledPins[0], 255 - red); // common anode: LOW = brighter
ledcWrite(ledPins[1], 255 - green);
ledcWrite(ledPins[2], 255 - blue);
delay(200);
}const byte ledPins[] = {38, 39, 40}The three pins are the red, green, and blue legs in that order. ledcWrite(ledPins[0], 255 - red)Writes 255 minus the value because this common-anode LED lights when its pin goes LOW. red = random(0, 256)Each colour gets a fresh brightness from 0 to 255, and setting all three at once mixes the shade. Optional side path · same circuit
pins = [38, 39, 40] # R, G, B
pwm0 = PWM(Pin(pins[0]), freq=1000)
r = random.randint(0, 1023)
pwm0.duty(1023 - r) # common anode: invert with 1023 - valuepwm0.duty(1023 - r)MicroPython's duty here is 10-bit, so it inverts with 1023 minus the value instead of 255.Same pins, same wiring. Run it in Thonny if MicroPython is set up; otherwise skip it — it should never block the Arduino-first path.
05 Understand, don't memorise
Any colour is three brightnesses
Day 7 turned one pin into a dimmer with PWM. Today you run that same dimmer on three pins — one for red, one for green, one for blue — and the colours add up in your eye. That single idea is the whole of colour on every screen you own, built from three numbers.
Three PWM dials
Each colour leg gets its own PWM channel — the Day 7 dimmer, running three times over instead of once.
0 to 255 each
Each channel is set to 8-bit, so a colour has 256 brightness steps from 0 to 255; three of them together reach millions of shades.
Your eye adds them
The red, green, and blue glows overlap under one lens and arrive at your eye as a single blended colour.
Equal makes white
With no colour winning — red, green, and blue at the same level — the mix stays neutral, dim grey low down and white at full.
Anode or cathode
The one shared pin sets the polarity, deciding whether a colour lights when its pin goes LOW or when it goes HIGH.
The model
colour = red + green + blue, each a PWM level from 0 to 255
Common anode vs common cathode
Three LEDs share one pin. Run that shared pin to 3.3V and you have a common anode, where each colour lights when its own pin goes LOW. Run it to ground and you have a common cathode, lit on HIGH. This kit is a common anode, so the sketch writes 255 minus your value and a bigger number still means brighter.
Why the numbers stop at 255
The channels are 8-bit, which gives 256 levels per colour, 0 through 255. That is the same ledc hardware from Day 7 doing the fast switching, while your loop just names one level for each of the three colours.
Why equal numbers look grey
When red, green, and blue are equal, none of them leads, so your eye finds no hue to settle on and reads neutral — grey at a low level, white at a high one.
06 Know it worked
Test & debug
Nothing prints to the screen today — the proof is the colour in the dome.
What you should see
- The RGB LED glows a colour.
- Every fraction of a second it jumps to a new random colour.
- It keeps changing for as long as the board has power.
The colours look random on purpose — each one is a fresh mix of red, green, and blue.
If it doesn't
- Only one colour ever appears? Check that colour's 220 Ω resistor and its GPIO wire — the other two legs may not be reaching their pins.
- Nothing lights at all? Check the common pin — it goes to 3.3V, not to ground.
- A colour is stuck full-on? Suspect the common-anode wiring or the wrong leg on that pin.
- Upload fails? Swap in a data-capable USB cable.
07 Make the idea yours
Try this: predict a colour, then mix it
The random sketch proves the board can mix. This proves you know the recipe. You'll predict three colours from their red, green, and blue numbers, then set those numbers by hand and check your eye against your maths. It fits inside today's 25 minutes.
Predict three colours
On paper, write the three numbers from 0 to 255 for orange, then purple, then white. Orange is a lot of red with some green and no blue; purple is red and blue together with green held low; white is all three at full. Notice that equal numbers should read as neutral grey or white.
Mix it by hand
In the sketch, swap each random(0, 256) for your fixed red, green, and blue number, upload, and compare the dome with your prediction. The code still writes 255 minus each value for the common anode, so your bigger number is still the brighter one. If a colour looks off, nudge the number and re-upload.
08 Learn it with a hand on the tiller
Coach me through it
Every lesson ships with a code and a machine-readable packet, so an agent can guide you with full context.
Lesson code
TSK-DAY09-RGB
Context packet
How the agent should behave: guide one physical connection at a time and wait for confirmation, teach that any colour is three PWM brightnesses from 0 to 255, explain the common-anode inversion on request, and help the learner predict then mix a named colour. Always check the common pin, wiring, board, and USB before changing code.
Keep your place
Finished Day 9?
Mark it complete — it shows on your course map, and your place is saved on this device.