ESP32 Master Notes | Notion

ESP32 GPIOs that can’t be used:

6, 7, 8, 9, 10, 11 : Used for Internal flash
0 : Boot mode control
2 : Boot strapping pin
15 : Strapping pin
34, 35, 36, 39 : Input only

PINS that can be used:

Category	Pins	Notes
SPI	23 (MOSI), 19 (MISO), 18 (CLK), 5 (SS)	SPI
UART	1, 3	Default UART TX/RX
Fully Usable	4, 5*, 12, 13, 14, 16, 17, 21, 22, 25, 26, 27, 32, 33	Pin 5 is already SPI SS, so might be in use

Current Design: Per-Node SS + Interrupt

Each sensor node requires:
- 1 dedicated Slave Select (SS) line
- 1 GPIO interrupt line
  - Upto 7 sensor nodes can be supported
Improved Design : Daisy-chained SPI (1 SS total)
- All sensor nodes share:
  - SPI MOSI/MISO/CLK
  - 1 shared SS line
- Each node still needs:
  - 1 GPIO interrupt line (unique)
- Upto 13 sensor nodes can be supported