[time-nuts] Trimble Acutime Gold PPS

Chris Albertson albertson.chris at gmail.com
Sun May 19 17:32:07 EDT 2013

Without a full schematic diagram about the only thing I can ask is if
yuremembered that for RS232 the control and data signals are reversed.

For rs-232 Tx and Rx use a negative (low) for a logic "one".  But DCD uses
the other convention with a positive meaning  one..   So if you can see the
serial data you have that correct.  try flipping the RS422 wire for the
control signal.

On Sun, May 19, 2013 at 2:03 PM, Miguel Barbosa Gonçalves <m at mbg.pt> wrote:

> Hi!
> I am struggling trying to convert my Acutime's PPS signal from RS422 to
> RS232 for NTP use.
> I am using this converter: http://www.dpieshop.com/quatech
> -sscvt500n-rs232-to-rs422485-serial-converter-p-282.html and I connected
> - Port A (T+) to R+ on the converter
> - Port A (T-) to R- on the converter
> - PPS+ to T+ on the converter
> - PPS- to T- on the converter
> On the RS232 part of the converter
> - TXD (pin 3) to computer pin 1 (DCD)
> - RXD (pin 2)to computer pin 2 (RXD)
> - GND (pin 5)to computer pin 5 (GND)
> all other pins are connected to the same pin on the computer except for the
> DCD on the converter which is not connected.
> I can see the serial time code on the computer yet the PPS (a long 400 ms
> one) doesn't seem to reach the computer.
> I've tried everything I could remember off and connecting the RS422 PPS+
> pin directly to the computer makes the NTP daemon stop randomly and losing
> the PPS signal. I really think I need to convert the PPS signal (30 meters
> long cable). Without PPS and using this converter NTP works fine. The
> problem is the jitter I am getting.
> I think I've exhausted every option with this converter and found this
> converter: http://www.ko4bb.com/~bruce/GPS_RS232_RS422_Transceiver.html.
> I might try it. Anyone here tried it or has any input for this situation??
> I also think that from a time nut perspective building my converter instead
> of using a black box will enable me to see what is the delay in the signal
> conversion.
> Any help would be highly appreciated.
> Kind regards,
> Miguel
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Chris Albertson
Redondo Beach, California

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