Chapter · SPI
A whole conversation
The four clock modes, a full transaction from the light going on to the light going off, how fast it can go, and several devices on one bus.
- 07Modes4 minMode 0 is the default and most chips accept it, so you rarely choose a mode. You meet the four SPI modes when a datasheet asks for another, or when a chip answers but its bytes arrive shifted. Check the mode first.
- 08A transaction4 minA whole SPI conversation lives between chip select falling and chip select rising. To read a register you send a command and an address, then clock out bytes that carry nothing while the peripheral fills them in.
- 09How fast4 minSPI has no speed of its own. The controller picks a clock for each peripheral, and the ceiling is whichever is slower, the peripheral or the controller's pins.
- 10More than one device4 minPeripherals share the clock and the two data wires, and each gets a chip select of its own. A daisy chain saves the pins by threading them into one long shift register, and pays for it in clocks.
Start at 07 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.