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uMPX GPS Setup
https://forums.stereotool.com/viewtopic.php?f=6&t=31081
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Author:  radiosean [ Tue Nov 09, 2021 11:28 pm ]
Post subject:  uMPX GPS Setup

Want to use uMPX with GPS to synchronize 2 transmitters on a SFN. As I understand, the encoder only needs NMEA via USB or serial. Appears the decoder side will also need 1PPS injected into the sound card. Does anyone know how that injection would be accomplished with ASI 5810 sound cards? My GPS receivers have serial and 1PPS outputs. Would the 1PPS be injected into the analog input of the sound card, or is it more complicated than that? I've been looking for a connection schematic, but haven't found anything. Thanks!

Author:  hvz [ Sun Nov 14, 2021 4:14 pm ]
Post subject:  Re: uMPX GPS Setup

Hi, does your 1PPS output have 1 line or 2? If it has 2, chances are that you can connect it, if the voltage levels aren't too high. Otherwise you might need to make some changes. We do know how to do it with certain receivers (I can't promise that it will work on all, and I need to look up the details), and we have convertor boxes from a 6-pin DIN to audio 1PPS + USB.

Author:  2Sense [ Tue Nov 16, 2021 7:35 am ]
Post subject:  Re: uMPX GPS Setup

I am also interested to know about this. Previously tried to get NMEA data into Steretool standalone for the uMPX encoder but had difficulties.
Had a GPS device connected via USB but couldn't figure out how to successfully use the name field. (ST expects data at 9600 baud but the USB device worked at a different rate, I think 4800 baud?)
Is this a possibility for time stamping on the encoder end?

Author:  hvz [ Wed Nov 17, 2021 10:57 pm ]
Post subject:  Re: uMPX GPS Setup

Odd - we're explicitly opening the device at that bitrate. If it only supports 4800 that might be a problem. Can you try to open it in a DOS box? You can just try something like
Code:
type COM4
and that will show you the data if the bitrate etc are set correctly. Which can be done with a command called "mode". If it's just a matter of also supporting 4800 that should be easy enough to add on our end, but I need to know first if it works with mode and type.

Example MODE call (this one works for the device that we're using):
Code:
mode COM3 baud=9600 parity=N data=8
So first set mode for the COM port that you're using, then use type to see the input. If it looks like readable text (basically a lot of numbers separated by commas), it works.

Author:  2Sense [ Sat Nov 20, 2021 7:14 am ]
Post subject:  Re: uMPX GPS Setup

Thanks Hans. I'd been trying with a G-STAR IV USB GPS (BU353S4). It appears fine as a COM port in Win 10 and when I tested at the time, I was able to receive NMEA data via a test application.
The test application was receiving at 4800 baud I think, but I could not get ST to recognize this data to timestamp uMPX.
When I get a chance (hopefully soon) I will post a few tests, including results of what you have suggested.

Author:  2Sense [ Sun Nov 28, 2021 3:53 pm ]
Post subject:  Re: uMPX GPS Setup

Just tested this. I could not get the commands you posted to work properly. Only once could I see text data which looked like NMEA, but I had set the port to 4800 baud?
Using PuTTY was more successful. Opening the port at 9600 baud gave odd characters, but at 4800 baud NMEA data seemed to pass data fine.

It seems that (as standard) the device passes NMEA at 4800 baud. Searching the internet revealed a guide and some software (for the SiRF chipset?) which can be used to change baud rate.
Running at 9600 baud now, Stereotool reads the NMEA data and gets 'GPS lock' for time stamping! :D

I guess the question now is whether or not it would be useful for users to be able to change COM port settings within ST?

Author:  radiosean [ Sat Dec 11, 2021 12:41 am ]
Post subject:  Re: uMPX GPS Setup

Finally....I've got GPS sync working on the bench using receivers purchased from eBay...

Image

The receiver has RS232, 1PPS and 10MHz outputs. On the encoder side, RS232 is connected to the serial port on the ST computer. On the decoder computers, RS232 is connected to the serial port and the 1PPS output is connected to the left audio input of the ASI5810 sound card. 10Mhz is not used. Everything locks up and looks right. Been running several hours and seems like it's going to hold up.

Only problem I'm having is that the ASI5810 ASIO driver does not show up as a device on uMPX. Had to use ASIO4ALL (not sure how this will affect timing between transmitters).

Will update again when we get everything installed at our towers, and get the additional GPS licenses purchased for the encoder and decoders.

Thanks Hans and everyone for the info!!!

Author:  2Sense [ Sun Dec 12, 2021 7:56 am ]
Post subject:  Re: uMPX GPS Setup

Thank you for sharing here. Please do let us know how it goes.

Author:  hvz [ Sun Dec 12, 2021 11:35 pm ]
Post subject:  Re: uMPX GPS Setup

Quote:
Just tested this. I could not get the commands you posted to work properly. Only once could I see text data which looked like NMEA, but I had set the port to 4800 baud?
Using PuTTY was more successful. Opening the port at 9600 baud gave odd characters, but at 4800 baud NMEA data seemed to pass data fine.

It seems that (as standard) the device passes NMEA at 4800 baud. Searching the internet revealed a guide and some software (for the SiRF chipset?) which can be used to change baud rate.
Running at 9600 baud now, Stereotool reads the NMEA data and gets 'GPS lock' for time stamping! :D

I guess the question now is whether or not it would be useful for users to be able to change COM port settings within ST?
So did setting the COM port to 4800 and then using type work, or not? If it did I can indeed add a pulldown menu with bitrates. But that's only useful if the mode command worked, otherwise something else must be going on.

Author:  2Sense [ Tue Dec 14, 2021 6:57 am ]
Post subject:  Re: uMPX GPS Setup

Using the commands you provided wasn't really successful - I got it working once at 4800 baud but it didn't seem quite right.
However, when using PuTTY instead, I could get NMEA data fine at 4800 via the COM port. Why might there be a difference?
I could try the pulldown menu if you think its worth adding?

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