RTS/CTS Control

[Jeff Bauman]

Are there any plans to enable RTS/CTS control for comm 1 ?  Can you reccomend a way to interface comm 1 with a standard VHF radio?  I have used a 5902 modem (Control Microsystems with the -m option) which controls rts/cts automatically, but it lists for $524

[support]

There is no plan to utilize the RTS/CTS control on COMM1.  There is normally no need to utilize flow control because the message exchange with the PLC is usually half-duplex. You send one ASCII string to the PLC and then wait for it to reply. Usually the modem have sufficient buffer capacity to take the message characters without needing the flow control.

The PLC can communicate at 38.400bps, but you can change it down to as low as 300 baud if need be (that will be really really SLOW). Typically 9600bps works great with most modem on the market.

A radio modem supplier who has tested their radio modem with our PLC is key Telemetering (http://www.keytelemetering.com).  They have tested the radio modem to work when the PLC communicate at 38,400bps.

Check the following thread for the contact person:

http://www.tri-plc.com/cgi-local/yabb/YaBB.pl?board=Support;action=display;num=1053447552

[Jeff Bauman]

These are fine for "Line-of-Site" Applications.  What I'm trying to use is "Standard UHF/VHF Radios" ie: Johnson, Motorola, Maxxon 5-watt to 40-watt.  A Bell-202 modem (Required for standard radios, are typically 1200 baud max.  To communicate over a radio, you must have the rts/cts to key up the radio.  I've found a low-cost bell 202 modem by tigertronics. But without handshake it appears impossible. http://www.tigertronics.com/rtx12.htm

[support]

If you run the PLC's serial port at 1200 bps or slower, then the PLC will output data at same or slower speed than the radio can handle. If you then tie the RTS and CTS together (on the radio) you might be able to get it to work.

Anyway, we don't have experience in such application. The above is just a suggesion/guess only.