There is only one case I know of where an 810LED display has a drop-in LCD replacement. This is in an ebikeling kit I bought in 2019 which has a 5 pin digital 810LED. It swaps with his SW900 LCD, and only that LCD. I have both displays and found they swap into his current controller, and the 810 is the better performer. To further confuse things, his kits from 2015-2017 used a 5 pin analog 810LED, which is not compatible. If you look inside, it's the usual 4 pin 10LED with a dummy wire.
Meanwhile, you get the 15 dollar 4 pin 810LED in lots of other bikes and ebike kits. It is an analog device. It outputs 1V for PAS1, 2V for PAS2, 3V for PAS3, and 4V for walk mode. That all it does. A compatible controller knows how to set the PAS level for each voltage. That 810LED is hardwired for 24, 36 or 48V. I own four or five of these, and have one installed on my first ebike kit.
A typical digital LCD display has 5 pins. It uses two pins to send data back and forth, much like.a USB interface. It can send commands to set PAS level, invoke Walk mode, and receive data such as speedometer info and watts coming back from the controller. It also gets error codes from the controller. Because all of this has no standards, the displays won't work with other peoples controllers.
Displays like the SW900 and S900 look identical, but are probably copied from someone like Kingmeter. They have different firmware and won't necessarily work. .
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And since they copy each other most displays have the same pinout, so you can hook them up in different controller. They will power up, but won't work. Often they will turn on the foreign controller, but cannot talk to it. In many cases, the controller has a default PAS and throttle is enabled, so the bike kind of works. Very confusing.