Chapter · I2C
Addresses
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.
- 04Addresses4 minEvery chip on an I2C bus has a seven-bit number, its address, and the controller puts it at the front of every message. The chip with that number answers and every other chip lets the message go by.
- 05Scanning the bus4 minA scan calls every address from 0x08 to 0x77 and listens on the ninth clock of each, where a chip that heard its own address pulls SDA low. It is the first thing to run when a module does not answer.
- 06Two chips, one address4 minTwo chips at one address both answer, at the same moment, on one wire. The scan shows one device, and every read returns a number built from both, with no error anywhere to say so.
Start at 04 and read down — the order is the order things get easier in. Or take the one with your part in it; every article stands on its own, and links back to whatever it needs.