ESP8266 Community Forum

- Wed Feb 20, 2019 4:07 pm #80678 I have a Wemos D1 mini and a (Drotek) Ublox M8N GNSS module. I want to connect these two via the Tx/Rx pins, and using Hardware Serial on the Wemos.
I connected the pins accordingly:
GPS...Wemos
Tx -> Rx
Rx -> Tx
5V -> 3V3
GND -> GND

The GPS module can be powered with 3.3 to 5V and the logic level on the Tx/Rx pins is 3.3V.
I configured the baud rate of the module to be 115200, and wrote a very basic sketch:

Serial.begin(115200); in the setup function
...
if (Serial.available() > 0) {...} in the loop function.

The condition above is never met. It appears no data is sent using the serial interface. Do you guys know what is wrong here ?

- Thu Feb 21, 2019 4:28 pm #80709 Update:
It seems the serial communication works if I'm using software serial on some two pins, other than Tx and Rx. This is not an option since I won't have any unused digital pins on my module.
Any help is greatly appreciated. It's 12 hours since I'm looking into this issue and I don't know what else to try out.

- Fri Feb 22, 2019 1:26 am #80717 Do you have the usb connected to your PC while running your sketch?
That won't work since you would have connected 3 devices on the serial bus: esp, PC (via usb/serial) and gps.
You need at least a simple LCD display to output the gps data while powering the setup via Vin (not usb since this activates most usb/serial chips).

- Fri Feb 22, 2019 4:57 am #80721 Shufti, thanks for your answer.

That won't work since you would have connected 3 devices on the serial bus: esp, PC (via usb/serial) and gps.

I thought this could be an issue, so I used a power bank to power the Wemos. I tried USB data cables, USB charge-only cables(I think on these the data pins are either not connected, or shorted). I desperation, at 3AM last night, I even 'modified' an USB cable to remove the data pins on both ends, but with no result.

You need at least a simple LCD display to output the gps data

I display the data using a Wifi Server, I guess it's the same thing.

while powering the setup via Vin (not usb since this activates most usb/serial chips).

I only powered the Wemos using the micro USB port. Do you believe the usb/serial chip is also activated when using charge-only USB cables, or the modified USB cable I made last night ?