Microchip Technology AVR-BLE Hardware User's Manual page 9

3.1.2.1 Overview
The on-board debugger implements a composite USB device that includes a standard Communications Device Class
(CDC) interface, which appears on the host as a virtual serial port. The CDC can be used to stream arbitrary data in
both directions between the host computer and the target: All characters sent through the virtual serial port on the
host computer will be transmitted as UART on the debugger's CDC TX pin, and UART characters captured on the
debugger's CDC RX pin will be returned to the host computer through the virtual serial port.
Figure 3-1. CDC Connection
PC
Terminal
Software
Info: As shown in
for receiving characters from the host computer. Similarly, the debugger's CDC RX pin is connected to a
UART TX pin on the target for transmitting characters to the host computer.
3.1.2.2 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.
Info: On older Windows systems, a USB driver is required for CDC. This driver is included in installations
of Atmel Studio/Microchip MPLAB
On Linux machines, the CDC will enumerate and appear as /dev/ttyACM#.
Info: tty* devices belong to the "dialout" group in Linux, so it may be 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#.
Info: For all operating systems: Be sure to use a terminal emulator that supports DTR signaling. See
Section 3.1.2.4 "Signaling".
3.1.2.3 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.
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2020 Microchip Technology Inc.
Debugger
Terminal
Send
CDC TX
USB
CDC RX
Terminal
Receive
Figure 3-1, the debugger's CDC TX pin is connected to a UART RX pin on the target
®
X IDE.
User Guide
Hardware User Guide
Target MCU
Target
Receive
UART RX
UART TX
Target
Send
DS50002956A-page 9