The firmware supports up to 8 external sensors of different types. Keep in mind that CC253x has limited performance. You cannot attach 8 sensors, 4 inputs, UART and get a good result. Some sensors cannot co-exist with each other.
You may add most external sensors on input or output pins. It does not matter. If a sensor has additional options like an address, I recommend adding it on an output pin. Otherwise, the firmware will use the default options for the added sensor.
Common Zigbee information for all external information:
Zigbee cluster: ZCL_CLUSTER_ID_GEN_ANALOG_INPUT_BASIC
ATTRID_IOV_BASIC_PRESENT_VALUE – the sensor value (single-precision float).
ATTRID_IOV_BASIC_DESCRIPTION – the value units (V – voltage, C – temperature, % – humidity, m – altitude, ppm – air quality, CO2, TVOC).
Zigbee commands: read