Sferalabs Iono Pi IPBB20R User Manual page 20

When these pins are configured as generic digital inputs, they are protected by a resistor
network, and pulled to ground when not connected. They accept positive voltage levels up
to 40Vdc.
The DI1-DI3 front-end circuits have 2.2kOhm pull-down and 4.7kOhm series resistors.
WARNING
Never apply voltage levels outside the specified operating limits to DI1, DI2 or DI3.
To use the TTLx/DIx lines as generic inputs, the corresponding jumper (see table below)
should be set across the two pins closer to the terminal block.
Set the jumpers across the center and the pin opposite the terminal block to use the input
as TTL I/O.
WARNING
Note that the Iono Pi board and the Raspberry Pi could be damaged if the jumpers are
configured for TTL mode and voltages outside the 0÷5V range are applied to the inputs.
19
INPUT MODE SELECTION JUMPERS POSITION
Pin
TTL2/DI1
TTL3/DI2
TTL4/DI3
Jumper
JP3
JP2
JP1
Iono Pi User Guide