Two wires, however many modules.
A microcontroller runs out of pins long before you run out of modules to connect. I2C puts them all on the same two wires, and each lesson here shows the part you cannot see.
Why every module can share two wires, who does the talking on them, and what the clock is for.
Every module has a number. How the ESP32 uses it, how to find every number on a bus, and what happens when two modules share one.
The numbered registers inside a chip, and one whole read of a temperature, a piece at a time.
Why every I2C wire needs a pull-up resistor, how big it should be, what too many of them do, and a 5 V module on a 3.3 V board.
Electricity
Volts, current, resistance and the mistakes that kill parts. 35 pages, true of every board.
35 articles →The other fundamentals trackPower and protection
Fuses, ideal diodes, TVS and lithium cells — every part that sits between a supply and something you would rather not replace. 13 pages, with part numbers.
13 articles →The other fundamentals trackMQTT
How a reading gets from a sensor to a phone, a laptop and a lamp without any of them knowing the others. Every lesson has a bench in 3D and in a VR headset.
10 articles →The other fundamentals trackSPI
The four-wire bus that chip after chip uses when it needs to be fast: a clock, two belts of bits, and a light that says who is listening. Every lesson has a bench in 3D and in a VR headset.
14 articles →The other fundamentals trackScreens
Every way a screen is fed, from a two-wire OLED to an eDP laptop panel: how much data a picture is, where the picture lives, and what has to keep moving. Every lesson has a bench in 3D and in a VR headset.
16 articles →The other fundamentals trackTCP and UDP
What a network adds to your data and what it leaves out: one-line cards that may be lost, and a novel cut into numbered strips that is pasted back together. Every lesson has a bench in 3D and in a VR headset.
12 articles →The other fundamentals trackUART
How two devices send bytes down a wire with no clock between them, only an agreement made beforehand: the idle line, the start bit, the data bits, baud, and what happens when the two sides disagree. Every lesson has a bench in 3D and in a VR headset.
12 articles →The other fundamentals trackRS-485 and Modbus
How a serial line is made to carry a long run and a crowd: a difference between two wires, a trunk with many taps, one driver at a time, the ends, and the Modbus conversation on top of it. Every lesson has a bench in 3D and in a VR headset.
12 articles →The other fundamentals trackCAN bus
How many devices share one pair of wires with no master: a hall of desks that shout or stay quiet, who speaks first, how a message is built and checked, what goes wrong, and the two ends of the rail. Every lesson has a bench in 3D and in a VR headset.
12 articles →The other fundamentals trackEthernet
How a cable carries a network: one shared channel and its collisions, what a frame holds and who it is for, hubs and switches, how a link comes up, the MAC, the PHY and RMII, and the three ways an ESP32 gets Ethernet. Every lesson has a bench in 3D and in a VR headset.
12 articles →The other fundamentals trackWi-Fi
How a frame crosses the air: radio waves and channels, why signal is not a bar count, how a network is found and joined, station and access point, sharing airtime, hidden stations, robust versus fast, sleep and security, and the ESP32 on the bench. Every lesson has a bench in 3D and in a VR headset.
13 articles →The other fundamentals trackLoRa
Small messages over a longer link: the chirp, spreading factor, bandwidth and coding, airtime, noise and interference, the rules where you live, collisions, a battery day, LoRa against LoRaWAN, and the ESP32 bench. Every lesson has a bench in 3D and in a VR headset.
12 articles →The other fundamentals trackZigbee
A low-power mesh, not Wi-Fi: the shared radio, three roles, names and joining, paths, a sleepy sensor and its parent, clusters and bindings, security, the controller side, failure, and the ESP32 bench. Every lesson has a bench in 3D and in a VR headset.
13 articles →The other fundamentals trackWorkshop
The hand skills. Soldering a joint that lasts, and reading the ones that will not. 2 pages, no circuit required.
2 articles →Next, in the ESP32 bookWires on the board
How two chips agree on what a line means, sorted by what it costs you in pins
9 articles, no board required →Next, in the ESP32 bookMessages on the network
Once there is no wire left to agree about, the question is who talks first
5 articles, no board required →