Lesson 2 of 5

B1 and a knob on A0

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// Read B1 and a knob on A0, and print them through the ST-LINK const int KNOB_PIN = A0; // PA0 const int BITS = 12; // ADC resolution in bits const int FULL = (1 << BITS) - 1; // 4095 at 12 bits, 1023 at 10 void setup() { pinMode(USER_BTN, INPUT); // PC13, R30 on the board pulls it up pinMode(LED_BUILTIN, OUTPUT); analogReadResolution(BITS); Serial.begin(115200); // Serial goes to the ST-LINK's COM port } void loop() { bool pressed = digitalRead(USER_BTN) == LOW; // B1 connects PC13 to GND digitalWrite(LED_BUILTIN, pressed ? HIGH : LOW); int raw = analogRead(KNOB_PIN); float volts = raw * 3.3 / FULL; Serial.print("A0="); Serial.print(raw); Serial.print(" ("); Serial.print(volts, 2); Serial.print(" V) B1="); Serial.println(pressed ? "DOWN" : "UP"); delay(250); }

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Read the blue B1 button on PC13 and a potentiometer on A0 with the full 12-bit ADC, and print both over the ST-LINK's virtual COM port. LD2 lights while you hold B1.

Press B1 in the figure, or let the script press it
No pull-up to wire: R30 is on the board
Wire the knob to 3V3: 5 V on an ADC pin can damage it

Pin	Connects to	What it does
`PC13`	B1 on the board (no wire needed)	Input with R30's 4.7 kΩ pull-up: LOW while pressed.
`A0`	The knob's middle leg (wiper)	ADC input, 0 to 3.3 V.
`3V3`	One end of the knob	The top of the knob's range: 3.3 V, never 5 V.
`GND`	The knob's other end	The bottom of the range.

Wire it in

Sensors and actuators this board drives, with the real connections.

PotentiometerSupply 3.3 V
Ends to GND and 3V3, wiper to A0: analogRead() gives 0-4095 after analogReadResolution(12).
Part pin Board pin
1 GNDWire colour black
W A0Wire colour yellow
3 3V3Wire colour red
Careful
Power it from 3V3, never 5V: an ADC input in analog mode takes 4.0 V at most, and reads 4095 for anything above 3.3 V.

All 8 parts on the STM32 Nucleo-F401RE page

Connects to

What it does

PC13

B1 on the board (no wire needed)

Input with R30's 4.7 kΩ pull-up: LOW while pressed.

A0

The knob's middle leg (wiper)

ADC input, 0 to 3.3 V.

3V3

One end of the knob

The top of the knob's range: 3.3 V, never 5 V.

GND

The knob's other end

The bottom of the range.

Wire it in

Sensors and actuators this board drives, with the real connections.

PotentiometerSupply 3.3 V

Ends to GND and 3V3, wiper to A0: analogRead() gives 0-4095 after analogReadResolution(12).

Part pin	Board pin
1	GNDWire colour black
W	A0Wire colour yellow
3	3V3Wire colour red

Careful

Power it from 3V3, never 5V: an ADC input in analog mode takes 4.0 V at most, and reads 4095 for anything above 3.3 V.

All 8 parts on the STM32 Nucleo-F401RE page

B1 and a knob on A0

Try it yourself

Serial monitor

Checks

Break it

Inputs

Parameters

Wire it in

B1 and a knob on A0

Try it yourself

Serial monitor

Checks

Break it

Inputs

Parameters

Wire it in