How do you put more than 32 devices on a single RS485 trunk ?

The simple answer is use a repeater but in practice one isn’t always necessary.

The RS485 standard is based on 32 devices. Since the standard was developed most RS485 chips present less than the full unit load originally specified. Today you get half and quarter load devices. Thus to see how many devices you can install you simply get the data sheets and add the loads. Look for “UL” on the data sheet. It stands for Unit Load.