The 40-pin connector is not populated, the X3 connector is populated with the pin header. Selection over the jumpers is not possible. The interface to the host system is on X3 with the following pin assignments:
| Pin # | Usage |
|---|---|
| 1 | GND |
| 2 | 3V3 |
| 3 | SPI: MOSI (Master-Out-Slave-In) |
| 4 | SPI: MISO (Master-In-Slave-Out) |
| 5 | SPI: CLK (Clock) |
| 6 | IRQ (Interrupt to host) |
| 7 | SPI: CS (Chip Select/Chip Enable) |
The crossed-out pins are not used in this configuration.
For the SPI interface, the Raspberry Pi acts as “master”, the IOL HAT as “slave”. The SPI mode is Mode 0 (CPOL=0; CPHA=0).
Ensure the correct pin assignment of the GPIO connector. Misalignment or rotation can cause damage on the host module and the IOL HAT. Note that the 3V3 and GND pins are not reverse-polarity protected.