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

[W7OBB]

I confirmed the gps module works by connecting it to serial and seeing the NMEA sentences separately.

The gd77 won’t turn on now that I have everything back together. I tried to connect the red/black wires to the 5 pin component like in the photo of the original post. Are those the best vcc/grd points?

[VK3KYY]

Are those the best vcc/grd points?

There are loads of places to get vcc and gnd

Scratch the insulation away from most the the Fill areas and you will find they are GND

Most of the chips have both vcc and gnd

[BD4SMY]

I also want to add gd-02 module in my Baofeng DM-1701B (like Retevis RT-84), but I don't know how to connect the wire. Is there anybody could help me? Thanks a lot!

Because I can only load the pictures which size is less than 250KB, maybe the chips' model is not very clear. The following is the details:

MCU -- Geehy-APM32F407VGT6
Modem -- Hongrui HR_C6000
RF -- AUCTUS AT1846S
ROM -- Winbond-W25Q128JVSIQ

[VK3KYY]

The GPS needs to be connected to the STM32 clone CPU chip (Geehy-APM32F407VGT6)

The pins are called GPS_RX and GPS_EN

PA10 GPS_RX is the serial data
PA9 GPS_EN is the power control signal

Note. You can't directly power the GPS module from the GPS_EN it can't produce enough current. You need to use a transistor(s)/FET(s) to amplify the signal from the GPS_EN to power the GPS

See the diagram. The pins are on the right side in the diagram. Sorry, I don't know the pin numbers, but because you will need to solder wires visually, then the diagram is probably better

PS. Where do you plan to put the antenna. From what I can remember fitting the antenna inside the radio seemed impossible, but perhaps you found a place for it.

Possibly you could remove the rotary control, becuase its functionality is replicated by the Up/Down or P1/P2 buttons, and fit the antenna in that location

I think personally I may consider removing the rotary control, and fitting a GPS antenna in that location.


PS.
I would not recommend you put the GPS module in the section of the radio for the RF PA. This could possibly damage the GPS module or may reset it when you transmit

UV380-DM1701_STM32_pins.png (84.14 KiB) Viewed 4925 times

[BD4SMY]

The GPS needs to be connected to the STM32 clone CPU chip (Geehy-APM32F407VGT6)

The pins are called GPS_RX and GPS_EN

PA10 GPS_RX is the serial data
PA9 GPS_EN is the power control signal

Note. You can't directly power the GPS module from the GPS_EN it can't produce enough current. You need to use a transistor(s)/FET(s) to amplify the signal from the GPS_EN to power the GPS

See the diagram. The pins are on the right side in the diagram. Sorry, I don't know the pin numbers, but because you will need to solder wires visually, then the diagram is probably better

PS. Where do you plan to put the antenna. From what I can remember fitting the antenna inside the radio seemed impossible, but perhaps you found a place for it.

Possibly you could remove the rotary control, becuase its functionality is replicated by the Up/Down or P1/P2 buttons, and fit the antenna in that location

I think personally I may consider removing the rotary control, and fitting a GPS antenna in that location.


PS.
I would not recommend you put the GPS module in the section of the radio for the RF PA. This could possibly damage the GPS module or may reset it when you transmit

@VK3KYY Thanks for your detailed reply!

How to place the antenna is indeed quite important. I Noted that @LY1RF used just 1/4 wave length wire as GPS antenna. His pictures are enclosed herewith: https://eglike.info.gf/nextcloud/s/gtK6wLjX3YyDWJw

IMG_20240122_135559.jpg (255.07 KiB) Viewed 4855 times

May I use same type 1/4 wave length wire? And about the GPS module, I plan to put the back of 3.5" earphone and 2.5" microphone which called K-type plug like @F1RMB. I want to use the small GP-02 module like @LY1RF, but not the bigger GP-02 Kit like @F1RMB.

QQ-20240125085557-2.jpg (254.09 KiB) Viewed 4859 times

However, first of all, finding the available "transistor (s)/FET (s)" is even more urgent. But I don't know which one can be used and how to connect because I have no electronic diagrams of DM-1701. Could you please help me again? thanks again.

PS: Your attached “UV380-DM1701_STM32_pins.png” is very useful for me! If you can give me the entire diagram, it's much more better.
BTW, I found the pin numbers diagram as attached.

APM32F407VGT6 100 pins.png (173.61 KiB) Viewed 4859 times

[LY1RF]

As power switch i've used MT9700

[BD4SMY]

As power switch i've used MT9700

Which one on your DM-1801 board? is there any parameter and diagram? Thanks.

[LY1RF]

gps enable from cpu goes to power switch and then to gps module , just follow red wire from cpu to mt9700 and then to gps module. MT9700 pdf you can find on google.

[BD4SMY]

gps enable from cpu goes to power switch and then to gps module , just follow red wire from cpu to mt9700 and then to gps module. MT9700 pdf you can find on google.

Thanks Ly1rf, I found the pdf about MT9700 pdf. As a beginner, I have some questions need to be verified:

1. Is MT9700 this one in following picture? Was this one added by you? Beside of the two pins which you connected the wire, what status are the others three pins? I guess you connected the pin 5 (VIN) to the VCC contact on the board which under the MT9700, right?

QQ-20240129214552.jpg (88.79 KiB) Viewed 4820 times

2. I find the wave of GPS is 19.05cm and Beidou's is 19.19cm. So, L1+L2+L3≈4.8cm, is it right?

WX_20240129211948.jpg (117.25 KiB) Viewed 4820 times

Is the soft wire the ground? I don't know its length is radom or not. Just hang in the air?

WX_20240129210613.png (189.82 KiB) Viewed 4820 times

3. About the GP-02 Module, I can see the bottom pins connnetion. Is it a resistance between the GPS Module's pin 2 (TXO) and MCU's pin 99? What's the value if it is, 10Ω since it is marked as maybe "100"? The pin 6 is connected with a button cell, what is its type?

Waiting for your reply with best regards!

[LY1RF]

Soft wire is center conductor of coax cable (~4.2cm) and works as active part of antenna, another part going to the left is shield part of cable and works as ground plane. You can take a look here for better understanding : https://www.electroschematics.com/24ghz ... l-antenna/