6.1.3 Command Examples
PTI Configuration
pti config 0 efruart 1600000
Configures PTI to use the "EFRUART" mode at 1.6 Mb/s.
Serial Port Configuration
serial config vcom handshake enable
Enables hardware handshake on the VCOM UART connection.
6.2 Virtual UART
The Virtual UART (VUART) interface provides a high performance application data interface that does not require additional I/O pins
apart from the debug interface.
The Wireless Starter Kit makes the VUART interface available on TCP/IP port 4900.
6.2.1 Target to Host
Target to host communication utilizes the SWO-pin of the debug interface through the ITM debug peripheral. This approach allows a
sleepy target device to enter all energy modes, and still wake up intermittently to send debug information. The baud rate of the SWO
data is locked to 875 kHz.
VUART utilizes ITM stimulus port 0 for general purpose printing. Silicon Labs' networking stacks utilize ITM stimulus port 8 for debug
printing. The data on port 8 is encapsulated in additional framing and will also appear in the Simplicity Studio Network Analyzer.
6.2.2 Host to Target
Host to target communication utilizes SEGGER's Real Time Transfer (RTT) technology. A full explanation of how this works can be
found in
J-Link/J-Trace User Guide (UM08001)
. Briefly summarized, RTT consists of a structure called the RTT Control Block, which is
located in RAM. This control block points to circular buffers that the debugger can write data into. The target application can then read
data out of this circular buffer.
The board controller will start searching for the RTT Control Block upon receiving data on TCP/IP port 4900. If the board controller is
unable to locate the RTT Control Block it will return an error message on the same connection. For the board controller to be able to
locate the RTT Control Block it has to be aligned on a 1024-byte boundary in RAM.
After initializing the RTT connection the target will only enter emulated EM2 and EM3 where the power consumption remains similar to
EM1. This is because RTT utilizes the debug interface which requires use of high frequency oscillators. Energy modes EM4S and
EM4H will work as normal. When debugging energy consumption it is therefore important to not send data on TCP/IP port 4900 as not
to instantiate the RTT connection.
6.2.3 Limitations
• Because the SWO-connection can be disabled by the debugger at will, it is important for the target application to verify that SWO is
enabled and configured before each transmission on the interface.
• After initializing host to target communication over RTT by sending data on TCP/IP port 4900 the target application will be unable to
enter EM2 and EM3. This is because RTT utilizes the debug connection of the target.
• VUART might not work reliably during an active debugging session. This is because there is contention over the target's debug inter-
face, and the board controller will defer accessing the target until it is made available by the host debugger.
• VUART is designed with the assumption that only the board controller will access the RTT control block. If the target application
uses RTT for other purposes, such as Segger SystemView, please refrain from using VUART.
UG431: EFR32xG22 2.4 GHz 6 dBm QFN32 Wireless Starter Kit User's Guide
Board Controller
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