Globalstar Product Management – Technical Support

Activating the GSP-1720 Control Port

How to activate the Control Port on GSP-1720:


  1. Modem does NOT have to be in view of the sky
  2. Antenna does NOT have to be connected.  If an Active Antenna is being used, the 7VDC does NOT have to be applied to pin 22
  3. Modem must be powered on via +5VDC
  4. Pin 13 must be grounded so that modem is in IDLE state
  5. Terminal Emulator program (e.g., MTTTY) must be running on a computer that is attached to the GSP-1720 Data_Port
  6. Data_Port_DTR must be asserted so that AT command processor is active
Activate the GSP-1720 Control Port:
  1. Issue AT and wait for the “OK” from the modem
    1. to confirm that the Data Port is active
    2. to confirm that you have your terminal emulator set to the correct baud rate.
  2. Issue AT$QCCTL=1    (wait for “OK”)    to activate the GSP-1720 Auxiliary port as the Control_Port
  3. Issue AT&W1   (wait for “OK”)     to write the parameters to profile #1
  4. Issue ATZ1 (wait for the OK) to load the modem settings for profile #1
    1. At this point, you won’t be able to submit any more AT commands on the Data_Port, because profile #1 uses the Control_Port for AT communications
  5. Then lift pin 13 so it will float
  6. Wait 20-25 seconds for modem to go through the transition from ON==>STANDBY mode, writing all required parameters to NVRAM
    • This will store the new baud rate into the Data_Port profile parameter table in NVRAM as the default.
  7. Turn off the power to the GSP-1720
  8. When you power on the modem the next time, the GSP-1720 will use the newly saved profile#
    1. The Control Port will be active as the AT Command port
    2. All AT commands must now be submitted through the Control Port
    3. The Control Port communicates at a fixed baud rate of 9600bps, 8/N/1, No flow control


Additional keywords:  1720, sdvm

Written by Joseph Crowley

August 19, 2017 at 11:45 am

Posted in Uncategorized

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