GPS (GP-02) kit module fitted in a GD-77

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F1RMB
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by F1RMB » Thu Feb 08, 2024 10:58 am

I know about that pin, but there is no PAD for it. What append in case that regulator get shorted for whatever reason, do you thing the MCU GPIO will survive ?

SQ1TAO
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by SQ1TAO » Thu Feb 08, 2024 11:55 am

F1RMB wrote:
Thu Feb 08, 2024 10:58 am
I know about that pin, but there is no PAD for it. What append in case that regulator get shorted for whatever reason, do you thing the MCU GPIO will survive ?
On EN leg is only pull up resistor and LP3992.
In your scenario fault may can short to ground or pull to 3.3 from regulator gd77. In my case I connect module to 3.3V rail.
In this application (vdd to module from 3.3v rail gd77) this LP3992 is obsolete, but we can use is as power switch.

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oe7abh
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by oe7abh » Fri Feb 09, 2024 2:50 pm

Daniel,

can you make a recommendation as to which modules work best for RT3s?
Which module would you install on the RT3s ?

Thanks, Alfred

eb4adc
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by eb4adc » Wed Feb 14, 2024 10:44 pm

SQ1TAO wrote:
Thu Feb 08, 2024 11:55 am
F1RMB wrote:
Thu Feb 08, 2024 10:58 am
I know about that pin, but there is no PAD for it. What append in case that regulator get shorted for whatever reason, do you thing the MCU GPIO will survive ?
On EN leg is only pull up resistor and LP3992.
In your scenario fault may can short to ground or pull to 3.3 from regulator gd77. In my case I connect module to 3.3V rail.
In this application (vdd to module from 3.3v rail gd77) this LP3992 is obsolete, but we can use is as power switch.

Hi could you put photos or draw a simple schematic to follow your explanations?
Other question: and ussing N/F pin of gp-02 module? In specs shows that in shutdown mode its consumption is 5ma. Could be affordable?
Thanks in advance.

SP2AM
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by SP2AM » Wed May 29, 2024 10:54 am

Also added GP-02 module to my GD-77:

- for powering on/off GPS I used voltage regulator that's already on GP-02. In my case it had different markings that LP3992 but was compatible. I lifted pin 3 up (EN), put kapton tape under pin to isolate it from PCB pad and connected pin 3 to pin 97 of mcu (green on download/file.php?id=1938 )

https://docs.ai-thinker.com/_media/gp-0 ... ations.pdf

- pin 99 (yellow) to TX pin on GPS-02 module

- 3.3v and GND from the same regulator as download/file.php?id=1935

- also had to mill case a bit and also mill small slots for antenna cable and the rest of wires

- gps antenna needs to protrude from metal case as much as possible; otherwise I wasn't been able to get any satellite coverage

- obviously forgot to insert battery connector gasket (orange one) when assembling and had to disassembly again

The result isn't great. Can't say it works. It finds 1-3 satellites with low signal, then looses them, find some again etc. That's when testing outside. No satellites found inside. Probably that antena (8x8x4mm) is still not exposed enough or just too small?

SQ1TAO
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by SQ1TAO » Thu May 30, 2024 3:17 pm

SP2AM wrote:
Wed May 29, 2024 10:54 am
Also added GP-02 module to my GD-77:

- for powering on/off GPS I used voltage regulator that's already on GP-02. In my case it had different markings that LP3992 but was compatible. I lifted pin 3 up (EN), put kapton tape under pin to isolate it from PCB pad and connected pin 3 to pin 97 of mcu (green on download/file.php?id=1938 )

https://docs.ai-thinker.com/_media/gp-0 ... ations.pdf

- pin 99 (yellow) to TX pin on GPS-02 module

- 3.3v and GND from the same regulator as download/file.php?id=1935

- also had to mill case a bit and also mill small slots for antenna cable and the rest of wires

- gps antenna needs to protrude from metal case as much as possible; otherwise I wasn't been able to get any satellite coverage

- obviously forgot to insert battery connector gasket (orange one) when assembling and had to disassembly again

The result isn't great. Can't say it works. It finds 1-3 satellites with low signal, then looses them, find some again etc. That's when testing outside. No satellites found inside. Probably that antena (8x8x4mm) is still not exposed enough or just too small?
In my case I NOT lift 3 leg on LP3992. Maybe your module is loop in on and off again and again... on GP-02 pcb is only pull up resistor connected to this leg. My gd77 still works and CPU without problem drive 3 leg to ground and power out GP-02 without fail.
When in settings GPS is OFF GP-02 is cut off from power supply and I see it in time working on one charge battery.

Outdoor 16sat without problem in that same small antenna. So antenna is not problem in your case.

SP2AM
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by SP2AM » Fri May 31, 2024 2:27 pm

Moved antenna a bit (had to file down its pcb a little), so almost entire ceramic part sticks outside of the metal case. Also soldered back EN pin to pullup resistor. Now it works well (even finds some satellites inside of building).

For EN pin "Maximum input current at EN IEN VEN = 0 V and VIN = 5.2 V - 0.001 µA", so nxp mcu should be able to deal with that without a need for pullup. I think that antenna not sticking out enough was the problem.

SQ5PTY
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by SQ5PTY » Sun Jun 16, 2024 7:58 pm

Hi,

I made this modyfication too. I have question about aprs's setting. If I set automatic mode and I set diffrent frequency (for example one of the repeater), that radio send APRS data. Of course in CPS I setted APRS settings correctly.

Best regards, !73

do1kka
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Joined: Sun Jun 23, 2024 9:09 pm

Re: GPS (GP-02) kit module fitted in a GD-77

Post by do1kka » Mon Jun 24, 2024 9:02 am

Hi!

I tried yesterday to add a GP-02 GPS module to my GD77 and the module was recognized so far by the device. Because I was not able to catch any satellites, so I decided to open up the device again und put the antenna more outside of the metal frame. Unfortunately, while opening the device, pin 99 of the MCU broke off... :(
Is it technically possible to use another pin of the MCU as RX for the GPS module (I could try to adapt the source code if necessary), or is this the only possible RX pin?

Thanks in advance for any information!

VK3KYY
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Re: GPS (GP-02) kit module fitted in a GD-77

Post by VK3KYY » Mon Jun 24, 2024 9:21 am

do1kka wrote:
Mon Jun 24, 2024 9:02 am
Hi!

I tried yesterday to add a GP-02 GPS module to my GD77 and the module was recognized so far by the device. Because I was not able to catch any satellites, so I decided to open up the device again und put the antenna more outside of the metal frame. Unfortunately, while opening the device, pin 99 of the MCU broke off... :(
Is it technically possible to use another pin of the MCU as RX for the GPS module (I could try to adapt the source code if necessary), or is this the only possible RX pin?

Thanks in advance for any information!
From what I can remember the only unused pin which supported UART Rx was pin 99

You can download the MCU data sheet (MK22FN512) from NXP https://www.nxp.com/docs/en/data-sheet/ ... 120SF7.pdf

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