GPS (GP-02) kit module fitted in a GD-77
Re: GPS (GP-02) kit module fitted in a GD-77
That is correct. The orbit data is only valid for a max of 4 hours. After that fresh data is needed.
Re: GPS (GP-02) kit module fitted in a GD-77
Thanks, Collin,
So, I just need a battery that last for only 4 hours. There is no point to provide backup power beyond that period. Is my understanding accurate?
Re: GPS (GP-02) kit module fitted in a GD-77
Isn't the almanac something that is used for getting a fix more quickly?
The almanac is valid for a longer period.
Re: GPS (GP-02) kit module fitted in a GD-77
Yes, the almanac last for longer so a longer battery life is still worth having. However it only helps with finding the satellites from cold. Modern multi channel receiver's are good at doing that even without the almanac.
The ephemeris data is needed for the actual position fix and that only lasts for up to 4 hours.
The ephemeris data is needed for the actual position fix and that only lasts for up to 4 hours.
Re: GPS (GP-02) kit module fitted in a GD-77
Thank you for all comments,
After trying with ML1220, ML920, and ML621 backup batteries. I have found out the warm boot on GP-02 will never happened beyond 4 hours. Based on Collins information, I believe this is because the module has to download the ephemeris data due to the expirations of the data it has. From my finding the ML621 is sufficient to back up the module for 4 hours. There is no need for a bigger battery.
One more thing, the "Battery" on the GP-02Kit is actually NOT a battery. It is a capacitor.
After trying with ML1220, ML920, and ML621 backup batteries. I have found out the warm boot on GP-02 will never happened beyond 4 hours. Based on Collins information, I believe this is because the module has to download the ephemeris data due to the expirations of the data it has. From my finding the ML621 is sufficient to back up the module for 4 hours. There is no need for a bigger battery.
One more thing, the "Battery" on the GP-02Kit is actually NOT a battery. It is a capacitor.
Re: GPS (GP-02) kit module fitted in a GD-77
Hi, I used the GP-02Kit to add GPS to the GD77.
I connected the power control to the N/F pin of GP-02Kit.
To reduce the consumption, I connected the EN pin of the LP3992 to the N/F pin through a 560 ohm resistor. The total consuption is thus less than 0.6mA (through the MCU "shorted" 10k pull-up).
I connected the power control to the N/F pin of GP-02Kit.
To reduce the consumption, I connected the EN pin of the LP3992 to the N/F pin through a 560 ohm resistor. The total consuption is thus less than 0.6mA (through the MCU "shorted" 10k pull-up).
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Re: GPS (GP-02) kit module fitted in a GD-77
I decided to go with the module (not the KIT) because we already have 3v3. To me, the kit is just a module with 5V0 to 3v3 regulator on it. In my opinion, it is a lot cleaner mod using the module.om1aeg wrote: ↑Wed Jun 25, 2025 11:57 amHi, I used the GP-02Kit to add GPS to the GD77.
I connected the power control to the N/F pin of GP-02Kit.
To reduce the consumption, I connected the EN pin of the LP3992 to the N/F pin through a 560 ohm resistor. The total consuption is thus less than 0.6mA (through the MCU "shorted" 10k pull-up).
I'm not sure about EN on the LP3992 regulator, Is it 5V logic? I don't think you can pull it down the way you are doing it. As I said, it is a lot better to getting rid of the regulator and N/F directly to the module.
BTW, I don't think the GP-02 support Active Antenna. I might be wrong, but that is how I understand it.
Re: GPS (GP-02) kit module fitted in a GD-77
Nope, I do the same. I connected EN pin straight to MCU pin and works perfectly more than yearKA1CM wrote: ↑Wed Jun 25, 2025 1:56 pmI decided to go with the module (not the KIT) because we already have 3v3. To me, the kit is just a module with 5V0 to 3v3 regulator on it. In my opinion, it is a lot cleaner mod using the module.om1aeg wrote: ↑Wed Jun 25, 2025 11:57 amHi, I used the GP-02Kit to add GPS to the GD77.
I connected the power control to the N/F pin of GP-02Kit.
To reduce the consumption, I connected the EN pin of the LP3992 to the N/F pin through a 560 ohm resistor. The total consuption is thus less than 0.6mA (through the MCU "shorted" 10k pull-up).
I'm not sure about EN on the LP3992 regulator, Is it 5V logic? I don't think you can pull it down the way you are doing it. As I said, it is a lot better to getting rid of the regulator and N/F directly to the module.
BTW, I don't think the GP-02 support Active Antenna. I might be wrong, but that is how I understand it.
So use EN pin in LP3992 is the best way to cut power to GPS when is OFF in software.
10k resistor on EN pin it's not a problem for CPU.
GP-02 kit have stock a passive antena but... can works with active antenna. GP-02 when turn on have 3.3v on antenna pin.
Re: GPS (GP-02) kit module fitted in a GD-77
I can't see how it will work. When the CPU pull the EN down there will be a current drawn pass the CPU pin and I believe that will cause some kind of damage.
As I said, I'm not sure if the EN on the LP3992 is 5V logic, but the better way to do it in my opinion (If one still insists to use the kit instead of the module) is to cut the VCC_5V and connect the EN directly to the CPU. Again, I don't think it is a good idea, just looks better than what it is.
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Re: GPS (GP-02) kit module fitted in a GD-77
Nope, after more than year and use only EN pin in LP3992 with directly connect to CPU and works great in my GD77. When GPS off in software then pull low, when on, pull up.KA1CM wrote: ↑Thu Jun 26, 2025 3:23 pmI can't see how it will work. When the CPU pull the EN down there will be a current drawn pass the CPU pin and I believe that will cause some kind of damage.
Snímka obrazovky 2025-06-25 134704.jpg
As I said, I'm not sure if the EN on the LP3992 is 5V logic, but the better way to do it in my opinion (If one still insists to use the kit instead of the module) is to cut the VCC_5V and connect the EN directly to the CPU. Again, I don't think it is a good idea, just looks better than what it is.
Snímka obrazovky 2025-06-25 134704 (1).jpg
If you use N/F pad when GPS module (in OFF state) draw ca. 5mA constantly.
When use EN leg in LP3992 current draw (in OFF state) is some uA because LP3992 draw.