I am looking to control a Dalite motorized projection screen with a RTI RP6 and RTI T4. The Dalite manual comes with the codes which I input into the RTI RS232 Command Library, but it is still not working. I am thinking that I am doing it wrong. The codes are listed here from the manufacture:
Up: @1U
Stop: @1S
Down: @1D
The baud is 9600
Parity is None
Stop Bits are 1
Data Bits are 8

I entered this into the RS232 command library software and got nothing any ideas?

are you using the SCB-200 interface? if not give us something to work with (exact model)

here is an extract which will be relevant for the SCB-200

- All commands shall begin with a “#” symbol.
- All values in the command shall be separated by a single ASCII space “ “.
- All commands shall end with an ASCII carriage return “”.
- Any spaces immediately prior to the shall be ignored.
- Any invalid commands should result in an ACK of “# ID ERR” and the appropriate
error code, as defined below. Commands issued to an invalid master / slave ID
shall be ignored.

Are the commands being routed to the right port? Or are you sending the command out to all ports? I know it's a simple thing but sometimes the simple things are whats wrong. And Springs no need for any comments. haha

ok working backwards, i checked their website and you are using the older SCB-100 interface. your codes look ok, but sometimes it is worth deleting them and retypeing (especially if you cut and pasted them from somewhere)
check that you have connected the screen to the screen 1 output.
ensure that you have connected the transmit pin of the cm-232 to the receive pin of the scb-100. if in doubt try reversing the RX & TX at the SCB end.
failing that you can always utilise two relay outputs of the RP-6 to simulate having a cold contact wall switch

This is how I usually control those type of screens. It's the same number of conductors as the RS232, and much less complicated. If I remember right you can also do a stop command by pulsing both contacts at the same time as well.