I've reviewed the Monarch Go LTE/4G modem for a road test. For that exercise, the modem was mounted on an Arduino-style shield. And there was a complete software example.

In this post, I am checking the lower levels of the modem. How to directly talk to it and get logging info out.

Most of the Monarch Go documentation is available under NDA only. I'm restricting the info here on what's available in public, or what you can find out without the NDA restricted info, by poking at the serial ports of the Starter KIT. and following the traces of the Arduino and Starter KIT PCBs.


Four UARTs

When you plug the board in your PC, you'll see that it enumerates 4 ports.

Each of them will have a function. By looking at the behaviour and examples, I could determine the function and settings of the first 2.

The Monarch is 1.8V. If you use the Arduino shield, be careful.

The UART that's connected to the Arduino headers (below called AT UART) has a 1.8 - 3.3 V translator. The other ones aren't 3.3V savvy.

The Starter KIT PCB seems



This is the 2nd COM port that enumerates when you plug in the Starter KIT.

It is also used in the example program of the road test.

From the source code, we know it's 115200, 8, N with RTS/CTS.

You can use this one to send AT commands. I started by typing all the commands used in the example code:



console UART:

This one you can find the settings from easily, because there is traffic on it by default.

You can put an oscilloscope or logic analyser on the Arduino shield and figure out the settings.

It's 155200, 8, N, no control.

This port shows what's happening inside the modem.

It also has an interpreter, but I haven't been able to get much out of it.



I found out about the interpreter on that port by connecting putty to it and pressing enter.

This is as far as I got with this at the moment.


UARTs enumerated as 3 and 4

These don't seem to do a lot. I can connect to those, but I see nothing happening. No reaction when I type, no data coming back.

Info is available under NDA. But that means I can't blog about it.


References on element14:

Monarch Go Arduino Shield Adapter Schematic

AES-SQN-MNRCHGO-SHLD1-G Hardware User Guide


Networking with Sequans Monarch Go - Part I (interesting article. With housing measures, also available here)

Sequans Monarch-Go Python Example  (for definition of the 4 enumerated ports, and interesting examples on MQTT and other client protocols available on board of the modem)