No clock wire. Only an agreement.
UART is how two devices send bytes with nothing but a wire each way and a ground, shown as two cottages whose switches and lamps are wired crosswise. Twelve short lessons, each with a bench you can press, on a laptop, a phone or in a VR headset.
Which wire goes where, how an idle line wakes the receiver with a start bit, how a byte becomes highs and lows, how a frame ends, and what baud means.
How a receiver reads with no clock wire, what a mismatch looks like, the buffer that can overflow, the faults a receiver can notice, and asking the other side to wait.
Why UART is not a voltage standard, and where all of this shows up on an ESP32.
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 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 →