Hello,
I just received two of the above mentioned modules. I was excited about the simplicity of the module.
I put in the SIM card, plugged in the USB and attached a 5V FTDI cable to J5. Opened HTerm and also the official m-center tool from u-blox. Then I pressed the Power-On button and started sending “AT\r” command @ 115200 baud.
Suddenly I start to receive random characters on the RX line. It goes on forever until I unplug the USB.
Ok maybe this board is broken. Tried the seccond one with the same behaviour.
What is happening here? It’s the most easy setup and it does not work! I tripple checked the whole schematic and it looks good. I also measured all the important voltages on the board and they are all present (1.8V, 5V IOREF, 3.3V).
So I guess, I received two broken boards or I fundamentally don’t understand the board…
Thanks for your help 
Best regards
Unfortunately our hookup guides don’t cover Ublox’s m-center, can you verify if you’re able to run example sketches as shown in the hookup guide? https://learn.sparkfun.com/tutorials/lt … troduction
Thank you TS-Brandon,
I also tried to run it like described in the hookup guide. Same behaviour. But I mean sending an AT command over an 5V FTDI cable is the most simple way to communicate with the module. And that is what I have done with the result of a infinite random output stream on RX.
Does your production make some tests before selling the modules? I guess, that would be appropriate for the price of the modules. Well, I will check If I can get refund with my local seller.
Thanks and best regards
Dear Sparkfun team,
Could you please try to reproduce my problems? I have four modules here now and all have the same behaviour.
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Connect USB cable
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Connect standard 5V FTDI cable to J5
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Press power button for 3 seconds
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Use terminal tool to connect with the FTDI cable @ 115200 baud
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Send AT command
→ RX starts receiving random characters forever
I also tried all the other baudrates with no result, not even the random characters.
It starts to be very urgent now…
Thank you very much!
Best regards
I apologize for the delay. Can you verify what example you ran using an Arduino, “I also tried to run it like described in the hookup guide.”
Our testbeds do test for the Serial interface. It is likely that there could have been a false positive. However, it is also equally likely that I may be missing some small pebble as it relates to your setup.
I understand that you’re stretched for time but due to the public health crisis our schedules have been altered. I have limited time at our physical office and I will try to assist as best as I possibly can.
Could you also try to provide a video of your operation, setup, and the resulting errors?
Thank you TS-Brandon,
I understand the problem with limited time, same here. Of course, I could do the things you requested from me and I understand, that you just support the shield as an Arduino platform. But I think, it really would be easier if you try to reproduce my setup as described in my last post. I want to use the shield through the TX and RX pin of the FTDI header. This is the most easy way to talk with the module as the FTDI cable also provides IOREF. I will not use an Arduino and neither the related libraries. Therfore a verification of the serial interface with just an AT command would be sufficient. If there are some major problems with long RX/TX lines (missing resistors at the level shifter), the board is not usable without an Arduino. But the hookup guide of the shield has a section called “FTDI Header”, which describes exactly what I want to do.
Best Regards