[time-nuts] Mounting GPS Antenna on Steel Roof
Brian Kirby
kirbybq at bellsouth.net
Fri Mar 7 22:55:28 EST 2008
The inverter is required because the Motorola GPS receiver uses TTL and
the PC serial port uses RS232.
RS232 uses a positive voltage of +3 to +25 volts to indicate a logic
zero, and a negative voltage of -3 to -25 volts to indicate a logic one.
Brian KD4FM
Bruce Griffiths wrote:
> Hal Murray wrote:
>
>>> Well, I plugged my Oncore UT+ into my PC and it didn't work until I
>>> put a level shifter in... no damage but no data either. So far I've
>>> been lucky in that every device I tried that needed a level shifter
>>> wasn't damaged by the lack of one.
>>>
>>>
>> The normal MAX232 type level shifters include an inverter.
>>
>> So even if the voltage levels work without a level shifter, the signal will
>> be upside down.
>>
>>
>>
>>
> To play safe, if one isnt sure that an inverter is required or not an
> exclusive OR can be used so that the signal can be inverted or not as
> required.
>
> Bruce
>
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