Can I connect the PPS output of a Garmin GPS 18x LVC to the PFI input of the PCI-1588?

[Lilian NF]

The Garmin GPS 18x LVC provides a PPS signal output, but I’m not sure if I can connect this wire to the PFI input of the PCI-1588.  The wire will be soldered to a SMB female connector (50 Ohm) and connected to the SMB connector of the PCI-1588. Nevertheless it isn’t a 50-ohm coaxial cable.  Is there some problem with this?

Please see below the specifications of the GPS 18x LVC and PCI-1588.

Regards,
Lilian

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GPS 18x LVC Technical Specifications
The GPS 18x LVC interfaces to a serial port. The unit accepts TIA-232-F (RS-232) level inputs and transmits voltage levels from ground to the positive supply voltage (4.0-5.5 Vdc), TIA-232-F (RS-232) polarity.

Input Voltage/Current: 4.0-5.5 Vdc, 90 mA
CMOS Serial Output Levels: 0 Vdc to Vin, between 4 and 5.5 Vdc [Asynchronous Serial, TIA-232-F (RS-232) Compatible Polarity]
PPS Output:
   1 Hz Pulse CMOS Output Accurate to 1 Microsecond Synchronized to GPS (UTC) Time.
   Pulse with programmable width, configurable in 20 ms increments from 20 ms to 980 ms.

The 5 meter (16 feet) cable contains wire for power, ground, receive, transmit, and PPS output.

GPS 18x LVC Pinout
1 - Yellow ...... PPS Output ........... 28 (wire gauge)
2 - Red ...........Vin ..........................26
3 - Black .........Ground .................. 28
4 - White .........Transmit Data ....... 28
5 - Black ......... Ground ................. 26
6 - Green .........Receive data ........ 28

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The wires 3, 4, 5, 6 will be soldered to a RS-232 female connector (DB9). The red/black wires will be soldered to a USB connector to supply 5.0 V.

The wire 1 (PPS output) will be soldered to a SMB female connector (50 Ohm) and connected to the PFI input.

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PCI-1588 Technical Specifications
PFI <0..2> connectors  ........................... SMB male, 50 Ω

PFI Inputs
The input terminals accept native +3.3 V signaling, but are +5 V tolerant. You should use 50 Ohm source termination when driving signals into PFI terminals.

PFI <0..2> Input Characteristics
Input impedance..................................... 1 k Ohm, nominal
Input coupling ........................................DC
Voltage level .......................................... 0 to +3.3 V, +5 V tolerant
Absolute maximum input voltage......... –0.5 V to 6.0 V
Minimum pulse width ............................ 36 ns
Input threshold
    Voltage threshold high.................... +2.3 V
    Voltage threshold low ..................... +0.8 V

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Related threads:

How to timestamp continuous analog data acquisition using USB-6009 and GPS timing board?

How to synchronize the PCI-1588 with the PPS signal of a external GPS receiver?

Message Edited by Lilian NF on 05-15-2008 05:09 PM

[Bruno M.]

Boa tarde Lilian,

Nos manuais encontram-se as faixas de tensão permitidas, assim como você colocou no forum.

Certifique-se de que a tensão de entrada não irá ultrapassar 6V para não correr risco de queimar a placa, que a tensão em nivel baixo esteja abaixo de 0,8V para ser interpretada corretamente e a tensão em nivel alto esteja acima de 2,3V para ser interpretada corretamente.

Saudações.

[henry Henry]

Hi Lilian,

Sorry to disturb you. Just now I also want to use the PPS generated by the Garmin GPS 18x LVC to do the synchronization. And I connect the red wire to the power in and black wire to groud. When I try to measure the PPS in the terminal of the yellow wire with the help oscilloscope, I got nothing! I can't get the pulses. Where did I make the wrong connection?

PS. I use 4 batteries which gives me about 4.5V. Do you think it is because the voltage is a little bit lower?

Thanks very much!

Regards,

Henry