ESP32-S3 board
The brain that runs your uploaded sketch.
01 First, know the pieces
What you need
Six things, and most of them are old friends from earlier days. 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.
Rotary potentiometer
The knob — its middle pin picks off any voltage between its two ends.
LED
The light you'll shade — it only works one way round.
220 Ω resistor
Sits in series with the LED to keep the current gentle.
5 jumper wires
Temporary, solder-free connections.
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. Two small circuits share the board today, so check the knob's side and the LED's side separately.
Pot middle pin
→GPIO 1
The divider's midpoint — the board reads this voltage as a number.
Pot outer pin
→3.3V
Sets the top of the knob's voltage divider at 3.3V.
Pot other outer pin
→GND
Sets the bottom of the divider at 0V.
LED long leg (+)
→GPIO 14 via 220 Ω
This pin shades the LED with PWM.
LED short leg (−)
→GND
Completes the LED's path back to zero volts.
Mind the LED's legs. The LED only lights one way round — long leg toward GPIO 14 through the 220 Ω resistor, short leg to ground. 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.
Stand the potentiometer on the breadboard so each of its three pins lands in its own row.
Wire one outer pot pin to 3.3V and the other outer pin to GND.
Run the pot's middle pin — the divider's midpoint — to GPIO 1, the wire the board reads.
Place the LED so its long leg (+) is on the GPIO 14 side and its short leg (−) heads toward ground.
Put the 220 Ω resistor in series between GPIO 14 and the LED's long leg.
Compare every wire to the chart before you plug in USB.
Open
Sketch_10.1_SoftLight.inoin Arduino IDE and upload it.Turn the knob slowly from end to end and watch the LED follow your hand.
04 Read just enough code
Read the code
The whole sketch is four working lines. One line sets up PWM on the LED's pin; the loop reads the knob and hands that number straight to the light. Switch to MicroPython if you'd rather see the same idea in Python — the wiring never changes.
#define PIN_ANALOG_IN 1
#define PIN_LED 14
#define CHAN 0
void setup() {
ledcAttachChannel(PIN_LED, 1000, 12, CHAN);
}
void loop() {
int adcVal = analogRead(PIN_ANALOG_IN); //read adc
int pwmVal = adcVal; // adcVal re-map to pwmVal
ledcWrite(PIN_LED, pwmVal); // set the pulse width.
delay(10);
}ledcAttachChannel(PIN_LED, 1000, 12, CHAN)Sets up PWM on GPIO 14 at 12-bit resolution, so brightness runs 0 to 4095 — the same span the ADC produces. analogRead(PIN_ANALOG_IN)Reads the knob's voltage on GPIO 1 as a number from 0 to 4095. ledcWrite(PIN_LED, pwmVal)Sets the LED's duty to that number. The two scales match, so the raw reading passes straight through as a brightness — the "re-map" comment overstates what this line does. Optional side path · same circuit
pwm =PWM(Pin(14,Pin.OUT),1000)
adc=ADC(Pin(1))
adc.atten(ADC.ATTN_11DB)
adc.width(ADC.WIDTH_12BIT)
adcValue=adc.read()
pwmValue=remap(adcValue,0,4095,0,1023)
pwm.duty(pwmValue)adc.width(ADC.WIDTH_12BIT)Sets the ADC to 12 bits so readings run 0 to 4095 — the same span the Arduino sketch reads.remap(adcValue,0,4095,0,1023)MicroPython's duty here is 10-bit, so the reading is squeezed from 0–4095 down to 0–1023 before it drives the LED.Same pins, same wiring. MicroPython's duty runs 0–1023, so this version remaps the reading down before writing it; the Arduino sketch matches the two resolutions so the number passes straight through. 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
One loop from hand to light
Everything you've learned about pins joins up today. Day 13 turned a voltage into a number and Day 7 turned a number into brightness; this sketch links them. The piece worth slowing down for is what makes the knob a voltage in the first place — a voltage divider, the pattern nearly every analog sensor in the kit leans on.
A voltage divider
The knob is two resistances in series across 3.3V and ground, with the wiper tapping their meeting point. Turn it and you move where the 3.3V splits, so the middle pin's voltage slides anywhere from 0 to 3.3V.
Voltage to number
analogRead measures that midpoint voltage on GPIO 1 and hands back a number from 0 to 4095.
One variable
pwmVal takes the ADC number straight across — both scales run 0 to 4095, so nothing needs rescaling.
Number to light
ledcWrite sets the LED's PWM duty to that number, so a higher voltage at the wiper lands as a brighter LED.
Every 10 ms
The loop runs again at once, so the light tracks your hand the moment you turn.
The model
voltage divider → ADC number → PWM duty → brightness
Why the knob is a voltage divider
Two resistances in series split the supply at their meeting point in proportion to their sizes. The knob makes that split adjustable — the wiper moves the boundary between the upper stretch of track and the lower one, so the midpoint voltage moves with your wrist.
The same divider, without a hand
Replace one half of the divider with a photoresistor and the split shifts on its own as the light changes — no knob to turn. That is how most of the kit's sensors reach the ADC, which is why this one pattern is worth knowing cold.
Why there's no map() call
The sketch sets the PWM to 12 bits on purpose. Both scales run 0 to 4095, so the ADC reading is already a valid duty and passes through untouched. When the scales differ — as in the MicroPython version — you remap first.
06 Know it worked
Test & debug
Nothing prints to the screen today — the proof is the LED under your fingertips.
What you should see
- Turn the knob to one end — the LED sits dark.
- Turn it to the other end — the LED reaches full brightness.
- Everywhere in between, the brightness follows the knob smoothly, with no jumps or dead spots.
Which end is dark depends on which outer pin you wired to GND — either way round is a working circuit.
If it doesn't
- LED stuck at full or stuck dark? Check the pot's middle-pin wire — it must reach GPIO 1.
- Turning the knob changes nothing? Check the outer pot pins — one to 3.3V, one to GND.
- LED dark at every knob position? Check the LED's direction and the 220 Ω resistor on the GPIO 14 side.
- Upload fails? Swap in a data-capable USB cable.
07 Make the idea yours
Try this: watch the raw numbers
You've seen the LED follow the knob. Now watch the number in the middle — the raw ADC reading the whole loop is built on — and use it to reason about which way the mapping runs. It fits inside today's session.
See the reading
Add Serial.begin(115200); to setup() and Serial.println(adcVal); inside the loop, then upload and open Serial Monitor. Turn the knob end to end and watch the number climb from 0 to about 4095 — that is the divider's midpoint voltage, digitised live.
Flip the mapping
Change the carry line to int pwmVal = 4095 - adcVal; and, before you upload, predict which end of the travel will now go dark. Upload and check — the raw numbers still climb the same way while the light falls, because you reversed only the mapping, not the reading.
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-DAY15-SOFTLIGHT
Context packet
How the agent should behave: guide one physical connection at a time and wait for confirmation, then make the voltage divider the centre of the explanation — the knob splits 3.3V, the ADC reads the split, and PWM turns that number into brightness. Always check wiring, board, port, and USB before changing code.
Keep your place
Finished Day 15?
Mark it complete — it shows on your course map, and your place is saved on this device.