ultimate gps and pc serial port

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adafruit_support_mike
 
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Re: ultimate gps and pc serial port

Post by adafruit_support_mike »

Probably, but I was referring to the software. A USB console cable won't do any good if the OS is looking for a signal on one of the serial pins.

ropesca
 
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Re: ultimate gps and pc serial port

Post by ropesca »

Yes, this is why I wanted to connect this GPS directly (even with an adaptor) to the serial port if it was possible.
adafruit_support_mike wrote:Probably, but I was referring to the software. A USB console cable won't do any good if the OS is looking for a signal on one of the serial pins.

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Re: ultimate gps and pc serial port

Post by adafruit_support_mike »

And that's why I asked what software on the computer will read the signal. What are you using?

ropesca
 
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Re: ultimate gps and pc serial port

Post by ropesca »

I'm using NTP (NTPD) Linux. The idea is to use this server as a Stratum 1 time server. But to make it work properly, ideally need to capture PPS and NMEA sentences.

I'm sucessfully using this Ultimate GPS with a Raspberry Pi with the same goal, but now I need to migrate my NTP Server from Raspberry Pi to a PC.

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Re: ultimate gps and pc serial port

Post by adafruit_support_mike »

Okay, that gives me a better idea of what you're trying to do.

The usual solution for UART to RS232 conversion involves a chip like the MAX322. Thing is, the MAX322's propagation rate is on the order of 500ns to 5ms. That's good enough for the NMEA sentences, but nowhere near fast enough for the PPS signal. Not only would you have an offset, variations within the MAX322 would play havoc with your PPS jitter tolerances.

For the PPS, you'll probably have better luck using a fast inverter. The trouble there is that all the really fast inverters are made for signals lower than 5v these days. Taking voltage thresholds into account, you'd probably have the best luck with something from the AHCT family. Those generally have a propagation delay on the order of 5ns, accept 3.3v signals as input, and produce signals which 5v systems can read as output.

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Re: ultimate gps and pc serial port

Post by ingenium »

Sorry to resurrect this old thread, but I'm trying to do the exact same thing. I've been using the adafruit GPS Ultimate breakout board on my raspberry pi for an NTP server and want to move it to an actual PC with a serial port.

Did you ever find a working solution?

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