Globalstar Product Management – Technical Support

Why does GSP-1720 reboot itself in my test rig but not in other products?

The GSP-1720 modem does not “spontaneously” reboot unless there is a problem with the implementation. This issue has been investigated countless times, and in the end, dedicated troubleshooting will almost always reveal the problem(s).

  1. Short Answer:  The GSP-1720 modem does not spontaneously reboot unless there is a problem with the implementation.
    1. This behavior is frequently a symptom of underlying power problems, failure to use the required wait times in powering the modem up, and shutting it down, and failure to use the proper wait times.
    2. If the modem is rebooting unexpectedly, detailed troubleshooting is required.  See below for “Troubleshooting Tips”
  2. Troubleshooting Tips:
    1. Typical problems that can cause unexpected modem reboots are:
      1. Power supply out of spec and does not meet one or more of the specifications for voltage, ripple, etc.
      2. Ground is varying, such that from the perspective of the GSP-1720, Pin_13 (Power_Enable_N) appears to be deviating from Ground, in which case the modem turns itself off when Pin_13 becomes ungrounded, and then the modem powers itself back on when Pin_13 is again pulled to GROUND
      3. Power supply is not strong enough for the combination of all of the items that are drawing power in the hardware integrator’s product — e.g., GSP-1720 modem, sensor devices, digital processor, disk drives, and other components
        1. When the power draw exceeds the stability envelope of the power supply, the voltage drops below the allowable minimum and the modem shuts down
        2. Once the modem shuts down, the power draw is reduced, the power supply again provides the correct voltage and provides the GND to Pin_13. Since conditions have returned to the allowable range, the modem boots up again.
        3. Note that as with most any other wireless device, the GSP-1720 modem draws different amounts of power when it is in standby mode, in operational mode, initiating a link, ramping up its Tx power to try to maintain a link, or conducting registration, initial handshaking and/or channel setup with the gateway.
      4. Audio Ground has been cross-connected to the GSP-1720 device ground or to the ground pin for one of the GSP-1720’s serial ports
        1. The Audio Ground must be completely independent from all other electrical grounds on the GSP-1720
        2. If the audio ground is connected to any other ground pins of the GSP-1720, the modem power will start to vary as soon as an audio link is connected and the modem’s power watchdog process will automatically shut down the modem as soon as the power is no longer within the specification
        3. The shut-down will occur within a few seconds (0 to 60) of when an incoming or outgoing audio link is connected.
        4. When the modem shuts down, the power returns to normal, and the modem reboots.
    2. To a hardware integrator
      1. Any of the above scenarios result in a situation which looks like the modem is “spontaneously” rebooting
      2. In fact, the spontaneous reboots are caused by instabilities in one or more elements of the environment (e.g., Power Supply Unit, Product circuitry, Unsteady ground conditions, Multipaths of connectivity and grounding)

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Additional keywords: GSP-1720 data grounding reset resetting, 1720

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Written by Joseph Crowley

January 16, 2014 at 7:10 pm

Posted in Uncategorized

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