Two wires, one difference, many stations.
RS-485 is how a serial line reaches far and serves many; Modbus is the conversation on top. Shown as a workshop bench with numbered stations, a foreperson who sends job tickets and a gauge that reads which of two rails is higher. Twelve short lessons, each with a bench you can press, on a laptop, a phone or in a VR headset.
Why a plain serial line fails on a long run, how two wires carry a difference, what common mode is, how many stations share one trunk, one driver at a time, and the two ends.
Who asks and who answers, what a request contains, where the data lives, the number trap in the manuals, how silence closes a frame, and what a reply, an exception and a timeout mean.
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 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 →