clarification on Baofeng DM-1701 and GPS

[VK3KYY]

Just a thought I had regarding the GPS function.

How does the software "know" that a GPS is available ?

On my radios (RT3S,DM-1701) without GPS, I can't even enable it.

When the firmware boots, when the status of the GPS us unknown, the firmware enables power to the GPS and then listens for data from the GPS module


All GPS modules send data constantly even when they do not have a position fix.

After data is received the firmware knows that a GPS is fitted and operational, and the GPS status changes to "Off", and then turns the power to the GPS off.

If you radio displays "Not fitted" for GPS either its not fitted or its not functional

[SQ9KCU]

No.

I checked the data sheet for the STM32F405 and neither of the USB pins PA11 and PA12 can be configured as UART Rx.

And just in case anyone asks about the GD77. The same applies. The USB pins on the MCU can not be used as UART, in fact on the MK22FN512 MCU used in the GD77 the USB pins can only function as USB, they can't be reconfigured even as GPIO

Maybe a software UART is possible?

https://github.com/liyanboy74/soft-uart
Vy 73
SQ9KCU

[OK2MOP]

The USB could clash with the software UART if you forgot to switch it, right?

I wonder, what about the PTT_EXTERNAL_Pin, what is its number on DM-1701, is it different from internal PTT (i.e GPIOE/GPIO_PIN_12)? Could we abuse this pin with sofware or HW UART by switching external PTT to GPS input? Since PTT on K connector uses the outermost contacts of both K connector pins, we could probably use shorter connector which would not disconnect MIC/SPEAKER on radio as normal K connectors do.

Alternatively, it could be possible to connect the GPS module to something like ESP-32 running code with USB host implementation (part of SDK), but you would loose the audio with normal connectors and it would require to implement some extra USB commands into the radio.

EDIT: If it actually is PE12, it cannot be remapped to any UART per the datasheet if I am reading it right

[VK3KYY]

PE12 can't be remapped to Rx data, the remapping is to flow control

If you are going to connect an external GPS and microprocessor then it can generate the APRS data and transmit those tones via the mic input
Products already exist which do this

[OK2MOP]

Yes, it could be even possible to use phone app for that and K to phone cables exist for around $15. But I was just not sure if this was the only use, maybe SQ9KCU waned to use it DMR in call positioning (DMR repeaters are quite widespread in PL) or satellite predictions as well.

[VK3KYY]

Yes, it could be even possible to use phone app for that and K to phone cables exist for around $15. But I was just not sure if this was the only use, maybe SQ9KCU waned to use it DMR in call positioning (DMR repeaters are quite widespread in PL) or satellite predictions as well.

Plugging-in anything disconnects the speaker and the mic, when it connects USB, so even if you did build an external device to act as USB host and send GPS position to the radio, you'd also need to build and external speaker mic system for DMR in call positioning.

If these things are that important to an operator, the could spend extra and buy a RT3S with GPS rather than a DM1701

For Satellite prediction, it seems like complete overkill to have a device you plug into the radio just to set the location, when you could use a mobile phone and enter the location.

[OK2MOP]

I totally agree, even if one wants to fit different GPS module and buy radio without GPS, it is better to buy a radio model which has at least space in casing and soldering pads broken out for GPS. I only bought this radio besides my other ones to use it as hotspot in future originally.

As a final question to this topic for DM-1701, if I enter my location in Status screen menu, is it transmitted also in the DMR call data or rather not?

[VK3KYY]

As a final question to this topic for DM-1701, if I enter my location in Status screen menu, is it transmitted also in the DMR call data or rather not?

Depends on the Channel TA settings for TS1 and TS2

[PR7LDR]

how can i activate my gps in Baofeng 1701 with opengd77 ?

There is no GPS in the DM1701

If you want to connect a GPS module to the MCU chip

NMEA serial data input pin is PA 10
Power enable is PA 9

Note.

The power enable pin is not able to supply the full current of a GPS module, you need to build a circuit of a PNP and NPN transistor to control the power to the GPS module from the power enable signal.

I have opened my DM1701 and there is very little room inside and it would be difficult to fit a GPS module and antenna inside this radio, however you could fit a GPS module outside the radio.

Thank you very much, it is valuable information. I was searching for this details for a while.