Board Controller Power; Efr32 Reset; Battery Holder - Silicon Laboratories EFR32xG21B User Manual

4.2 Board Controller Power

The board controller is responsible for important features, such as the debugger and the AEM, and is powered exclusively through the
USB port in the top left corner of the board. This part of the kit resides on a separate power domain, so a different power source can be
selected for the target device while retaining debugging functionality. This power domain is also isolated to prevent current leakage from
the target power domain when power to the board controller is removed.
The board controller power domain is not influenced by the position of the power switch.
The kit has been carefully designed to keep the board controller and the target power domains isolated from each other as one of them
powers down. This ensures that the target EFR32 device will continue to operate in the USB and BAT modes.

4.3 EFR32 Reset

The EFR32 Wireless SoC can be reset by a few different sources:
• A user pressing the RESET button
• The on-board debugger pulling the #RESET pin low
• An external debugger pulling the #RESET pin low
In addition to the reset sources mentioned above, a reset to the EFR32 will also be issued during board controller boot-up. This means
that removing power to the board controller (unplugging the J-Link USB cable) will not generate a reset, but plugging the cable back in
will, as the board controller boots up.

4.4 Battery Holder

In radio applications with high output power, peak current consumption will exceed the current sourcing capacity of a coin-cell battery.
To support evaluation of the EFR32 Wireless Gecko in situations where powering the kit from a wired USB connection is impractical, for
instance during range-tests, the kit is supplied with a battery holder for 2 AA batteries.
To use the battery holder, first set the power switch in the BAT position. Then attach the cable to pin 1 and 2 on the expansion header,
orienting the connector so the black cable cable goes down towards pin 1, and the red cable up towards pin 2.
Warning: There is no reverse voltage protection on the VMCU pin! Ensure that the battery holder is connected the right way. Failure to
do so may result in damage to the radio board and its components.
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Put power switch in BAT position
Figure 4.2. Battery Holder Connection
UG428: EFR32xG21B 2.4 GHz 10 dBm Wireless Starter Kit User's Guide
Connect battery holder
to EXP header.
- Pin 2 (up): Red wire
- Pin 1 (down): Black wire
Power Supply and Reset
Rev. 1.0 | 15