MTX1
Manual
Serial Bridge
Serial Bridge
The serial bridge can connect the XMEGA to a host application (ie: terminal emulator) over
USB. The XMEGA simply uses one USART as it would with, for example, RS232. There is no need to
learn the USB protocol or use a USB library. On the host side, the MTX1 will appear as a virtual COM
port. Speeds of up to 2Mbps are supported.
Configuration
Before using the serial bridge, it must be configured to be compatible with the target. This
configuration is stored in EEPROM. There is no need to duplicate the settings on the host side, as
communication between the host and MT X1 will always be the maximum supported USB speed, and
the other parameters are ignored by the host. Only the connection between the USB AVR and the
XMEGA use these settings. Note that when configuring the speed to be manual, it is possible to set
the speed higher than 2MHz, but the maximum speed supported by the USB link is 2MHz. The serial
bridge is configured in configuration mode (jumper on, button not pressed).
Serial Bridge Configuration Options
Configuration Option
Possible Values
Speed
2M, 1M, 500K, 250K, 125K, 76.8K, 57.6K, 38.4K, 19.2K,
9600, 2400, manual
Baud Rate Register
0x0000 0x0FFF (if manual selected as speed)
Clock 2X
1X, 2X
Clock Mode
async, sync
Data Bits
5, 6, 7, 8, 9
When in synchronous mode, the USB AVR is the master, so the XCK pin is enabled as an
output. The XMEGA must enable its clock pin as an input and be configured as a slave. When using
9bit data frames, two bytes are sent or received for every frame. The first byte simply contains the 9th
bit, thus the first byte will always be 0 or 1. The second byte contains the rest of the 8 bits.
June 2, 2015
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