LTE Cat M1/NB-IoT Shield - No communication over serial

Wireless & IoT Cellular
1

Hi,

I am attempting to connect to the SARA-R4 over serial (UART) as a breakout board using an Arduino. I have connected the 5V from the Arduino to the 5V shield pin, one of the GND pins, and then the TX on the board to RX on the shield and vice versa. Finally, I have closed the IOREF jumper to 3.3V as my board does not have an IOREF pin. Additionally, I have connected pins 5 and 6 for the power.

So far, I have been unable to get the device to work at all. The power LED turns on, but the SparkFun library hangs when ‘initialising the LTE shield’ using the examples.

Using a simple Serial Passthrough, I am unable to register any response when sending ‘AT’ over the serial lines at any baud rate (even using carriage return + new line, nothing appears at all in the serial monitor) after pressing the power button, regardless of the setting of the soft/hard serial switch.

A factory reset does not seem to help at all either. I’ve also tried having a card in and out, and still nothing in the serial console.

Have I done something wrong in terms of hardware set up? It really doesn’t seem that complicated but maybe I’ve missed something obvious.

Thanks for any assistance

2

From the description It is not clear whether you use hardware or software serial. IF you use an Arduino Uno the TX/RX (pin 0 and 1) are used to communicate between the Arduino and the serial monitor/PC . Connecting the TX/RX from the LTE to the same pins will not work. As an Arduino Uno only has one serial, you will have to use SoftSerial. Put the switch to SW and use pins 8 and 9 communication. See the hookup-guide for more info.

3

Hi,

The Arduino I am using has two hardware serial ports, one for the USB, and one on pins 13/14. These are Serial and Serial1 in Arduino code. I have connected pins 0 and 1 on the LTE shield to pins 13 and 14 on my board. These pins work reading from a GPS device, but not the LTE board.

Thanks

4

Hmmmm, sounds like something fishy is going on. If you could provide photos of your setup, that would be much appreciated. It is possible that the serial lines have defected, however, we do QC our products before we package and stock them.

Thanks in advance.

5

I had to resolder the serial port switch before I could get serial comms to my arduino.