Minimum Set of RS232 for Globalstar
Question: What is the minimum set of RS232 signals for Globalstar? Can we use simply TX and RX, or do we need to have more handshaking signals? The issue is that we have minimal handshaking lines; we prefer to use TXRX only, but we can do CTS/RTS at a pinch.
Answer: The Integrator’s Reference Manual has a comprehensive discussion about flow control for the first generation of Globalstar equipment (GSP-1600, GSP-1620, GSP-2900). We require CTS/RTS to begin with. You can jumper CTS/RTS and convert the modem immediately to software handshaking using AT+IFC=1,1 but if you don’t have CTS/RTS jumpered, the modem will ignore the AT command because it will think that you have no hardware flow control. If you choose to use software flow control, it is important to remember that you will have to reassert the AT+IFC command each time the modem is rebooted.