We’ve included a USB port on the modem, to allow for direct access to the modem chip (firmware upgrades, development, etc). It is not required in normal operation.
Similarly, the power reset button is there. Also not required in normal operation as that is under ESP32 control.
Antenna connection is via SMA header to external antenna connection (picture attached, to illustrate).
We’ve had to change to nano-sim. Still seeing if a bigger sim card is possible, but space is tight so nano may be the only way.
We need to ‘key’ the expansion ports in some way, to avoid inserting the wrong way round.
Currently using round pins for the expansion ports, but it seems that the industry standard is square pins. Square peg in a round hole. Discussing with manufacturer.

On 22 May 2017, at 10:47 AM, Mark Webb-Johnson <mark@webb-johnson.net> wrote:

For your Monday morning - some modems.

This should give you an idea of how the expansion can work. Each expansion module is self-contained and entirely optional. These modules extend what the base product can do.

First two are 3G and 4G. They have their own power supplies (to provide the needed 4V for modem operation).

Regards, Mark.

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