OpenGD77

SQ1TAO wrote: ↑

Sat Jun 28, 2025 5:28 am

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.

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.

Can you provide schematic diagram? I still not so sure if I follow.

KA1CM wrote: ↑

Thu Jun 26, 2025 3:23 pm

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.

Attention, the power supply is from 3V3, not from 5V (red pen). The 5V power supply is only on the schematic for the GPS module kit from PDF document, in reality the power supply is 3V3. There is no risk of damaging the processor. The current through the processor pin is around 0.6mA.

I used the schematic of GP-02 kit from this document, I did not redraw the internal wiring of the GPS Kit, the power supply there is marked 5V but I power the module from 3V3. https://eu.mouser.com/datasheet/2/975/6 ... 193653.pdf Figure 5, page 11.

om1aeg wrote: ↑

Sat Jun 28, 2025 8:46 pm

Attention, the power supply is from 3V3, not from 5V (red pen). The 5V power supply is only on the schematic for the GPS module kit from PDF document, in reality the power supply is 3V3. There is no risk of damaging the processor. The current through the processor pin is around 0.6mA.

I used the schematic of GP-02 kit from this document, I did not redraw the internal wiring of the GPS Kit, the power supply there is marked 5V but I power the module from 3V3. https://eu.mouser.com/datasheet/2/975/6 ... 193653.pdf Figure 5, page 11.

Hi OM1AEG, I understand you use the schematic from the document. My comment is the Gp-02 kit does not make with the option to shutdown the LM3992 in mind, the EN pin of LM3992 is tie to Vcc via 10Kohm resister, it does not matter if the Vcc is 5 or 3.3. the best way, in my opinion, to shutdown the LM3992 is to remove the 10K resister and connect MCU pin97 directly to EN pin of LM 3992, as the schematic I've already provided.

Again, I can not see any benefit of using GP-02Kit. In my opinion, using GP-02 Module is a much cleaner MOD.