One channel, then a line each.
Ethernet began as one shared cable that every station listened to, and became a switch with a line for each. Shown first as a radio room with one channel and a dispatch desk, then as real hardware drawn as plain blocks: the cable, the PHY, the MAC and the wires between them, and the classic ESP32, the S3 and the P4. Twelve short lessons, each with a bench you can press, on a laptop, a phone or in a VR headset.
Why a cable, one shared channel and its collisions, what is inside a frame, who a frame is for, and how a hub became a switch.
How a link comes up, the MAC and the PHY and the seven wires between them, and how a frame reaches an IP address.
The classic ESP32 with an outside PHY, the ESP32-S3 over SPI, the ESP32-P4 with no Wi-Fi radio, and how to choose one and find the fault.
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 trackI2C
The two-wire bus nearly every sensor module speaks, from the beginning. Every lesson has a bench in 3D and in a VR headset.
12 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 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 →