Inventor kit, Basic: Arduino examples

Arduino sketches for the Basic manual of the Soldered Inventor kit, built around the NULA DeepSleep ESP32-S3.

Every program in the manual is in this repository as the same text, so you never have to retype one.

What is on the board

An ESP32-S3 with a CH340 USB-serial chip, an onboard WS2812B RGB LED, a PCF85063A real-time clock and a Qwiic connector. Deep-sleep current is in the single microamps.

Getting started

1. Install the board

1. In the Arduino IDE, open File -> Preferences and add this URL to Additional boards manager URLs:

   https://espressif.github.io/arduino-esp32/package_esp32_index.json
   

2. Open Tools -> Board -> Boards Manager, search for esp32 and install esp32 by Espressif Systems.
3. Select Tools -> Board -> ESP32 Arduino -> Soldered NULA DeepSleep ESP32S3.

2. Install the CH340 driver

The USB-C port runs through a CH340. Without its driver the board never appears as a serial port, so there is nothing to pick in Tools -> Port. Windows and macOS both need it; on Linux it is already in the kernel.

Driver and troubleshooting: docs.soldered.com/ch340-drivers

3. Install the libraries

Open Tools -> Manage Libraries and install these three, all by Soldered Electronics:

Library	Needed by	Header it provides
Soldered TMP117	5.1, 6.2, 7.1, 7.2, 7.4	Soldered-TMP117.h
Soldered Library for Relays	5.2, 7.1, 7.4	Relays-SOLDERED.h
Soldered PCF85063A RTC Arduino Library	6.1, 7.2	PCF85063A-SOLDERED.h

Sections 0 to 4 need no libraries at all.

4. Open a program

Each program lives in its own folder, named like the file inside it. Open it with File -> Open and follow the chapter that uses it.

The programs

Every program here is the same text as on its page in the manual, so you can copy it from either place. They are in the order the chapters teach them.

1. Run your first program

Program	What it does
0.0_First_Light.ino	The smallest thing the board can do: light the RGB LED that is already on it.

2. Switch things on and off

Program	What it does
0.1_First_Blink.ino	The first example of the kit.
0.1_Two_LEDs_Taking_Turns.ino	Two LEDs on IO38 and IO39 taking turns.
0.3_Traffic_Lights.ino	A lit spot walking along five LEDs on IO38 to IO42.
0.3_Dark_Running_Light.ino	A dark spot walking along five lit LEDs on IO38 to IO42.
0.3_Traffic_Lights.ino	A car traffic light on IO38, IO39 and IO40, the four-phase kind: red, red and yellow together, green, yellow, and round again.

3. Read a button

Program	What it does
2.1_Floating_Button.ino	Reads a button on a pin that nothing is holding, so the reading drifts.
2.1_External_Pull_Up.ino	Reads a button on a pin held HIGH by a 10 kOhm pull-up resistor to 3V3.
2.1_External_Pull_Down.ino	Reads a button on a pin held LOW by a 10 kOhm pull-down resistor to GND.
2.1_Internal_Pull_Up.ino	Reads a button using the pull-up resistor that is built into the chip.
2.1_Button_Bounce.ino	Samples a button every 50 us after a press and prints how long it rattles for.

4. Measure with an analog pin

Program	What it does
0.2_Reading_A_Potentiometer.ino	Reads a potentiometer and prints it two ways at once, as raw ADC counts and as millivolts, so the Serial Plotter draws both as traces you can watch while you turn the knob.
2.3_Photoresistor_Resistance.ino	Measures the photoresistor's own resistance from the voltage at the junction of the divider, so you can pick a fixed resistor to pair it with.
2.3_Photoresistor_Hysteresis.ino	Calibrates the light range, then switches an LED on two thresholds, so light sitting right on the switching point cannot make it flicker.
2.3_Photoresistor_Single_Threshold.ino	Calibrates the light range, then switches an LED on one threshold, so you can watch it flicker when the light sits right on the switching point.
2.3_Photoresistor_Percent.ino	Calibrates the light range over ten seconds, then reports the light as a percentage of that range.

5. Fade an LED

Program	What it does
1.2_Gamma_Fading_And_RGB_Colour_Mixing.ino	Ramps an LED linearly and then with a gamma curve so you can compare them back to back.

"6. Project: a night light"

Program	What it does
1.3_Night_Light.ino	A night light that fades up as the room gets dark, combining the photoresistor divider from T10 with the gamma-corrected PWM from T12.

7. Capacitors, diodes and transistors

Program	What it does
3.1_Measuring_An_RC_Time_Constant.ino	Charges a capacitor through a resistor, captures the rise into a buffer, and prints the measured time constant next to the calculated one.
3.2_Diode_Forward_Voltage.ino	Logs a diode's forward voltage against the current through it while you turn a pot, so you can see that the drop is a curve rather than the 0.7 V everybody quotes.
3.3_Transistor_Base_Resistor_And_Saturation.ino	Sweeps the base drive of an NPN transistor with the potentiometer and measures load current, base current and the ratio between them.

8. Buzzers, servos and shift registers

Program	What it does
4.3_Driving_A_Buzzer_Through_A_Transistor.ino	Drives a passive buzzer through an NPN transistor from the + row, with a flyback diode.
4.3b_Buzzer_Loudness_From_A_Pot.ino	Drives a passive buzzer through an NPN transistor at one fixed frequency, with a pot setting the duty cycle and so the loudness.
4.3c_Buzzer_Held_Steady.ino	Drives the pin of a passive buzzer's transistor steadily high, to show that a steady voltage makes no sound.
4.3d_Buzzer_Duty_Steps.ino	Holds a passive buzzer at its resonant frequency and steps the duty cycle through 5, 10, 25 and 50 %.
4.2_Servo_Pulses_Without_A_Library.ino	No servo library.
4.1a_Eight_LEDs_From_Three_Pins.ino	Drives eight LEDs from a 74HC595, times three different ways of getting a byte into it, and then walks a single lit bit across the row.

9. Qwiic modules

Program	What it does
5.1_Scanning_The_Bus_And_Reading_Temperature.ino	Scans the I2C bus and prints every address that answers, so you can see what is really connected.
5.1_Scanning_The_Bus_And_Reading_Temperature.ino	Reads temperature from the TMP117 twice a second and checks every reading is a real one.
5.2_Relay_Switching_With_Hysteresis_And_Lockout.ino	Switches a Qwiic relay from a pot.
5.2_Relay_Switching_With_Hysteresis_And_Lockout.ino	Switches a Qwiic relay from a pot, with a hysteresis band but no minimum interval between switches.

10. Deep sleep and waking up

Program	What it does
6.1_Deep_Sleep_Wake_Sources_And_RTC_Memory.ino	Two counters show what survives deep sleep and what does not.
6.1_Deep_Sleep_Button_Wake.ino	Two counters show what survives deep sleep and what does not.
6.1_Deep_Sleep_Timer_Or_Button_Wake.ino	Two counters show what survives deep sleep and what does not.
6.2_Checking_A_Sensor_Alert_Flag.ino	The TMP117 keeps converting on its own and decides for itself when the temperature has left a band, then latches a flag.

11. Four projects

Program	What it does
7.1_Thermostat_With_Relay_And_Alarm.ino	A cooling thermostat.
7.2_WiFi_Temperature_Logger.ino	Sends a message every minute, the moment the temperature moves a full degree, or whenever the button is pressed.
7.3_Two_Sensor_Sun_Tracker.ino	Two photoresistors either side of a paper strip turn a servo needle towards the brighter one, with a dead band and a rate limit to keep it from shuffling on its own noise.
7.4_Bench_Controller.ino	Five jobs sharing one loop, none of them waiting for the others.

Continuous integration

Every example is compiled for the NULA DeepSleep ESP32-S3 on every push by the Compile examples workflow, so anything on the main branch is known to build.

The Advanced manual has its own repository with longer programs and bigger projects: Soldered-NULA-Inventor-kit-Arduino-project-examples-Advanced.

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