[ntp:questions] OT: GPS18x LVC failure

Rob nomail at example.com
Sun Oct 11 12:53:09 UTC 2009


David Lord <snews at lordynet.org> wrote:
> David Lord wrote:
>> David J Taylor wrote:
>>> OT: GPS18x LVC failure
>>>
>>> My GPS18x LVC stopped working a couple of days ago.  There appears to 
>>> +5V going into the unit, and the serial output is stuck around -5V 
>>> with no signs of data on the 'scope.  Garmin have accepted the unit 
>
> I'm guessing you hit (-) rather than (+), otherwise something
> odd as with my unit the supplies are +5V and 0V, output spec
> is 0V to +5V. Where was the -5V generated? If the -5V was real
> then it would indicate some sort of internal fault.

No, it is normal for an RS232 output to output positive and negative
voltages.

Where was the -5V generated?  Internal to the device.  Using a DC-to-DC
convertor, often a charge pump using some diodes and capacitors.

This is not a fault.




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