TYT MD-9600, add GPS later?

ve7mdt
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Re: TYT MD-9600, add GPS later?

Post by ve7mdt » Mon Dec 19, 2022 7:33 am

Great work, Roger.

The reason for the RS-232 signal is that it can travel much further in a cable w/o problem while a TTL signal is very susceptable to degradation of the signal quality over long distance. Most external GPSr back in the days are all RS-232 signalling. I still own modules that are mixed I/Os: BT, RS-232 and Compact Flash, for example.

VK3KYY
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Re: TYT MD-9600, add GPS later?

Post by VK3KYY » Mon Dec 19, 2022 8:29 am

I had not previously come across 10V RS232.

I have seen 20V RS232 using native voltages, but that was a long time ago..

The problem with the 10V signals from the module I bought was that the signal is inverted as well as being higher voltage.

If it wasn't inverted a simple voltage divider would have fixed the problem.

However 3.3V or 5V signals down a couple of meters of wire seems to be OK

UA0LMC
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Re: TYT MD-9600, add GPS later?

Post by UA0LMC » Mon Dec 19, 2022 6:37 pm

VK3KYY wrote:
Mon Dec 19, 2022 8:29 am
I had not previously come across 10V RS232.

I have seen 20V RS232 using native voltages, but that was a long time ago..

The problem with the 10V signals from the module I bought was that the signal is inverted as well as being higher voltage.

If it wasn't inverted a simple voltage divider would have fixed the problem.

However 3.3V or 5V signals down a couple of meters of wire seems to be OK
IIRC, RS-232 standard allows logical "1" to be anywhere between -3 and -15...-20 volts, and logical "0" from +3 to +15...+20 volts.

Inverted signal is not a big deal - use a small BJT or MOSFET to invert it once again. One extra part compared to a divider.
Or if you have access to GPSr PCB - you may just remove or bypass the TTL-RS232 level converter. Most likely it's max3232 or similar IC.

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Re: TYT MD-9600, add GPS later?

Post by ve2wkr » Wed Jan 25, 2023 12:49 am

hi!
So I ordered a GPS Module Ebyte E108-GN02D for about US$6. It has a built-in antenna, and a backup battery all in a 2cm square package.
I installed it in the front of my MD-9600 that had no GPS. I used double-sided installation tape to stick it to the plastic case on the left side of the radio
The antenna is pointing forward toward the display PCB. There is a gap of approximately 5mm between the antenna and the display PCB.
I figured that I would try this installation first and see if it worked.
To my surprise, this setup works 10 times better than the TYT built in GPS!
It acquires from cold start in about 2 minutes. After that it is pretty much instantaneous, as by the time I get into the GPS menu, after power up, it already has a position lock.
It appears to update the position at a higher rate then the H210 GPS module used by TYT. It always maintains 12 satellites lock and reports a position error or 0 m. ( maybe there is a rounding error in the software, and the error is less than 1m )
The installation took 30mins and the wiring is according to the picture in this thread.
To make it clear: the GPS module in internal to the radio and not visible.
Thanks for giving me this idea!
73's
Luca

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Re: TYT MD-9600, add GPS later?

Post by VK3KYY » Wed Jan 25, 2023 2:05 am

Thanks

That sounds like a good solution.

Unfortunately, I still have not had time to test the latest external GPS module I ordered from AliExpress ;-( But the previous modules I ordered worked well after I modified them to output the correct voltage signals.

Potentially the module you found may also fit in the UV380/RT-3S, and would work better than the one supplied with the GPS version of the radio

VK3KYY
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Re: TYT MD-9600, add GPS later?

Post by VK3KYY » Wed Feb 08, 2023 10:26 pm

I've now received and tested that eByte branded Chinses GPS module and initially it was very slow to acquire satellites

Very much like the GPS module in my RT3S.

I waited 10 minutes and it had not found any satellites, so I left it powered all night and this morning it had acquired 6 satellites

I'm using it indoors, with the unit next to the window, so it would probably work better if it was outside, but I'd say that it is not as good as come other / larger modules.

However, it is better than the GPS in the RT3S because it has a backup battery on the PCB, so it always does a "warm start" meaning it already has data from the last time it was running and hence will acquire much more quickly.

BTW. The data sheet for the eByte module I bought is here.

https://www.ebyte.com/en/downpdf.aspx?id=1125


I'm not sure if there is room inside the GD-77 case, as this module could potentially be a way to add GPS to the GD-77, albeit, I'm not sure if the MCU/CPU chip has any spare pins which can be used for Serial data

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