Network Connection Issues; Condition; Solution; Brownout Issue - Digi XBee 3 Cellular LTE-M User Manual

Troubleshooting

Network connection issues

Condition

The XBee Smart Modem is not joining the network,
(Initalizing), 0x22 (Registering to Cellular Network) and 0x25 (Cellular Network Registration Denied).

Solution

Some things to check are:
The antennas are connected correctly to the device.
n
The SIM card is seated properly in the device.
n
APN is set correctly.
n
If you had to change a modem parameter, check to make sure you have reset the module
n
using the FR command
such as CP, N#, BM, or BN.
Note The default APN configured in the kit should allow the XBee Smart Modem to get on the network
with the SIM included in the kit. However, you may program the APN explicitly to 10569.mcs if you are
having difficulty registering with the network.

Brownout issue

The XBee 3 RF Module uses a Silicon Labs EFR32MG System on Chip (SoC). Silicon Labs has announced
an intermittent restarting issue with EFR32MG revision B SoCs which can be caused by voltage
brownout or supply dips during power-on. The information below is provided to help you avoid this
condition.

Voltage brownout

This issue may occur if the supply powering the XBee VCC pin dips momentarily into the range of
approximately 1.2 to 1.8 V. When the supply returns to normal levels the SoC may not restart properly
and enter an unresponsive state. You must fully power cycle the XBee to recover from this state. The
failure rate tends to increase with slower ramp down rates of the power supply; for more details see
RMU_E203 — AVDD Ramp
specified in Power

Power-on discontinuities

This issue is similar to the voltage brownout issue. The SoC may fail to start if, during power on, the
supply powering the VCC pin experiences discontinuities in the voltage rise (in other words, dips) while
the voltage is in the range of approximately 1.2 to 1.8 V. You must fully power cycle the XBee Smart
Modem to recover from this state. The failure rate tends to increase with slower ramp up rates of the
power supply; for more details see
ramping your power supply steadily to the normal operating range.

How to distinguish revision B parts

Silicon Labs has corrected these issues in revision C of their SoC. We are printing the SoC revision on
the XBee label to make it easy to distinguish. The revision letter is located on the bottom right corner
Digi XBee® 3 Cellular LTE-M/NB-IoT Global Smart Modem User Guide
or by pressing the reset button, especially if you have changed settings
Issue. If you keep the power supply within the operational voltage range
requirements, the conditions to cause this failure are never met.
RMU_E203 — AVDD Ramp
Network connection issues
AI (Association Indication)
Issue. The issue can be avoided by
is cycling between 0xFF
314