How to set up FONA 3G With Raspberry

[adafruit_support_mike]

Have you reconfigured the Pi3 to make its GPIO Serial port work properly?

By default, the Pi3 has a software-based UART connected to the GPIO header's TX and RX pins. The UART's baudrate is derived from the CPU clock, and the Raspbian kernel automatically changes the CPU clock speed depending on the system load. The clock slows down when the CPU is idle to save power, and speeds up to keep the system responsive when the CPU is busy.

That can fool a loopback test running on the RasPi, because the UART is always in sync with itself.

This page has more information about the issue, including instructions to make the GPIO Serial port work properly:

https://www.raspberrypi.org/documentati ... on/uart.md