LC29HEA: problems with uart port!?

IoT Modules GNSS Module
1

Hello, unfortunately, I have not yet solved the problems I have with the LC29HEA module.
I also did this experiment: using a serial adapter I connected the UART port to the USB port of my laptop where I installed QGNSS (see photo).
After some time the mode indicated for the position is always the same: GPS SPS MODE (SINGLE with the gnss master or swmap apps).
If I connect the GPS via USB port I have no problem (both with QGNSS and with the Android apps): I easily switch to float and then to fix.
So I deduce the above:
a) The LCHEA module has some problems (firmware) managing corrections via uart;
b) My LCHEA form is damaged;
c) Maybe I need to change some settings via “command console”.
Am I the only one having this problem!?
It would be nice to have a response from Quectel’s technical office.
Good day

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2

Hi @falajons

  1. Can you send commands via UART? Does the module respond?
  2. When testing via UART and USB, make sure that other hardware conditions except the interface remain unchanged.
  3. Check whether the TX and RX levels of the UART are consistent with those of the UART serial port board.
3

Thanks George for your assistance.

  1. I sent commands via uart: I see them in the console but I don’t receive any response or they have no effect.
  2. I confirm that the hardware and software conditions in the test I performed are identical (apart from UART instead of USB).
  3. what does it mean to check the levels: do I have to measure the voltage on the pins with a tester? thank you very much
4

Hi @falajons

  1. From the information you provided, we can conclude that: under the condition that the software and hardware remain unchanged, USB communication is normal, but UART is not as expected.
  2. Please confirm the communication voltage of UART? 1.8V, 3.3V or 5.0V? You can use a multimeter to measure the voltage of TX and RX of LC29H. Confirm whether the voltage matches.
5

ok george,
question 1) yes with usb no problem but with uart it doesn’t work all other conditions being equal;
question2) I measured the voltages: VIN = 3.3V - TX = 3.3 V - RX = 2.8/2.9 V.

What suggestions!?
thank you and have a good day

6

Hi @falajons
The voltage test result you provided meets the requirements. Please perform the test as described in the following figure.
image
Refer to the figure below for the hardware pin diagram

image
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7

Thanks George for your assistance and patience. Unfortunately, before you answered me, I tried to connect (solder) two wires directly to the TX and RX pinouts (I first checked the hardware diagram) of the LC29HEA chip because from previous tests done with flying wire I had output data. Unfortunately the soldering was done clumsily with inadequate equipment with the following result: the GPS module connected to the USB-UART turns on and the built-in LEDs flash correctly but the position data is no longer transmitted. I then asked a friend with suitable equipment to desolder the wires to bring it back to its initial condition. However, perhaps the “omelette” has already been made and the form is perhaps no longer usable. I’ll let you know. A thousand thanks