“This was not the first Cellular modem I have been working on. However, it is the first modem working properly. The LTE technology is more future proof than GSM that my earlier modem were using. My first application is using SMS communication. This may sound historical, but I have my good reasons. One thing to consider in your code is that the received messages need to be read immediately so that the serial buffer is not overrunning. The chip may have som setting to overcome this challenge but it works at least in Arduino C.”
