There are 2 ways to mirror from iPad, iPhone (4 or later), or iPod Touch (4th Gen or later):

1. Use an Apple original "Lightning Digital AV Adapter" or "USB-C Digital AV Multiport Adapter" to connect your device to a ViewSonic projector. You might encounter no signal if you don’t use APPLE original adapter.

2.If your projector is equipped with WI-FI function, use AirPlay mirroring to project wirelessly and make sure that the projector and the source are within the same sub network. Please refer to this FAQ for more information, If AirPlay or screen mirroring isn’t working on your device.