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

[VK3KYY]

Anyone else tried this? Very interested in adding gps to my 77 but don’t want to screw it up.

Like the idea of a less invasive mod if one exists.

There is no other less invasive way to do this

[W7OBB]

First off thanks for the amazing tutorial @F1RMB!!

I have all the parts and my GD-77 is in pieces on my desk but I can't tell how the GP-02 is connected. It looks like you are only using the VCC and GND pads but its hard to tell in the pic which wires are going to which pads? Can you clarify or provide another photo?

How does the GPS data get to the GD-77 module if you aren't using the RX?

Also did you consider placing the GP-02 in a different location on the frame? There appears to be other spots that wouldn't requires routing out part of the frame?

Thanks!

[SA0BUX]

First off thanks for the amazing tutorial @F1RMB!!

I have all the parts and my GD-77 is in pieces on my desk but I can't tell how the GP-02 is connected. It looks like you are only using the VCC and GND pads but its hard to tell in the pic which wires are going to which pads? Can you clarify or provide another photo?

How does the GPS data get to the GD-77 module if you aren't using the RX?

Also did you consider placing the GP-02 in a different location on the frame? There appears to be other spots that wouldn't requires routing out part of the frame?

Thanks!

I see a yellow and a red that goes down to the STM32 CPU which I guess is data, and a red and black that goes to a transistor? that seems like the power feed.
Or Both blacks can be ground.
I think you only need tx out from the module.

[LY1RF]

About connections to cpu :

Code: Select all

* GPS functionality has been added to the GD-77, DM-1801 and DM-1801 firmwares
None of these types of radios was originally available with GPS, so operators will need to fit a GPS module inside their radio, and connect the data and power control connections directly to the CPU chip
GPS data needs to be connected to pin 99 and power control to pin 97. Becasue pins 98 and 100 are not used, it is safe, to bridge between 97 and 98 for power control and between 99 and 100 for data, and bridging pins makes it far easier to solder to the CPU

And here you can see my gps module install in dm1801. As gps antenna i've used just 1/4 wave lenght wire

https://eglike.info.gf/nextcloud/s/gtK6wLjX3YyDWJw

[VK3KYY]

GPS data needs to be connected to pin 99 and
Power control to pin 97.

Becasue pins 98 and 100 are not used, it is safe, to bridge between 97 and 98 for power control and between 99 and 100 for data, and bridging pins makes it far easier to solder to the CPU

I wrote this

Power control is not essential. You can just connect the 3.3V rail in the radio to the GPS power input pin. But if you do this the GPS will be consuming current when the radio is on, and this will flatten the battery more quickly

The CPU chip can not directly supply enough current to power the GPS module, hence you need to use a FET etc
I think Daniel usef a FET connected to Pin 97 to control the power to the GPS module.

[W7OBB]

Thanks all this is super helpfull!

@LY1RF can you annotate your photo? I don't have a dm1801 so unsure what you added and what was already there. I have both the gp-02 circuit board with the gps antenna taped to the back (which I removed like the original poster) and also the raw gp-02 module like you have. The raw module is much smaller and would be much easier to find a spot for.

[F1RMB]

The location of the GPS module is a bit tricky, because you can have shorts due to thickness, metal can and backup battery.

[W7OBB]

I got everything wired up based on the photos and info but it won’t power on.

@F1RMB can you provide a wire diagram so I can double check everything?

[VK3KYY]

I got everything wired up based on the photos and info but it won’t power on.

@F1RMB can you provide a wire diagram so I can double check everything?

When you say it won't power on, what do you mean ?

Did you try supplying power to the GPS module directly, e.g. from the Vcc/3.3V pad where the SWD pads are i.e the row of 5 pads near the edge of the board

If you supply the GPS with 3.3V it should consume over 50mA and on its Tx output, if you look on an oscilloscope or logic analyser you should see the Serial data , 9600 baud NMEA

[F1RMB]

Wiring is easy, VCC & GND to power the board, TX to MCU pin for the NMEA data, that's it (when power control is not used).