Microchip Technology SAM-IoT Wx v2 Hardware User's Manual page 9

Host computer will be transmitted as UART on the CDC TX pin of the debugger, and UART characters captured on
the CDC RX pin of the debugger will be returned to the Host computer through the virtual serial port.
Figure 4-1. CDC Connection
Info: As shown above, the CDC TX pin of the debugger is connected to a UART RX pin on the target for receiving
characters from the Host computer. Similarly, the CDC RX pin of the debugger is connected to a UART TX pin on the
target for transmitting characters to the Host computer.
4.1.2.2 Operating System Support
On Windows machines, the CDC will enumerate as Curiosity Virtual COM Port and appear in the ports section of the
Windows Device Manager. The COM port number can also be found there.
Important: On the older Windows systems, a USB driver is required for CDC. This driver is included in
installations of MPLAB X IDE.
On Linux machines, the CDC will enumerate and appear as /dev/ttyACM#.
Important: The tty* devices belong to the dialout group in Linux, therefore it is necessary to become a
member of that group to have permissions to access the CDC.
On MAC machines, the CDC will enumerate and appear as /dev/tty.usbmodem#. Depending on which terminal
program is used, it will appear in the available list of modems as usbmodem#.
Important: For all operating systems, ensure to use a terminal emulator that supports DTR signaling.
Refer to the
4.1.2.3 Limitations
Not all UART features are implemented in the on-board debugger CDC. The constraints are outlined here:
• Baud rate: Must be in the range of 1200 bps to 500 kbps. Any baud rate outside this range will be set to the
closest limit, without warning. Baud rate can be changed on-the-fly.
• Character format: Only 8-bit characters are supported.
• Parity: Can be odd, even, or none.
• Hardware flow control: Not supported.
• Stop bits: One or two bits are supported.
4.1.2.4 Signaling
During USB enumeration, the Host OS will start both communication and data pipes of the CDC interface. At this
point, it is possible to set and read back the baud rate and other UART parameters of the CDC, but data sending and
receiving will not be enabled.
When a terminal connects on the Host, it must assert the DTR signal. As this is a virtual control signal implemented
on the USB interface, it is not physically present on the board. Asserting the DTR signal from the Host will indicate to
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User Guide
SAM-IoT Wx v2
Hardware User Guide
DS70005506A-page 9