Datasheet

MT-X1S Manual
routed to a header, to be used for other purposes. External pull resistors are installed to keep the
peripheral pins at a defined state during boot or when the peripheral is disconnected. They pull chip
select lines to the deselected state to minimize power consumption. Most solder jumpers are
connected by default. To disconnect for the first time, a small trace connecting the two jumper pads
must be cut. To reconnect, create a solder bridge across the pads. Jumper J1 can be soldered to
connect the USB shield to ground. The USB specification calls for the USB shield to be connected to
ground on the host side only. However, it may be desired to ground this on the device side. An 0603
SMT component may be soldered on the solder jumper pads as well.
USB Serial Bridge
The USB Serial bridge allows the XMEGA to communicate with a computer over USB by
simply using a USART. There is no need to learn the USB protocol or utilize a USB library. All USB
functionality is handled by the USB AVR (AT90USB162). It simply relays bytes between the XMEGA
and the host. The MT-X1S uses two pins on USART F (RX and TX) in asynchronous mode and three
pins (adding XCK) in synchronous mode. Optionally, a USB ready signal is available on the XCK pin.
To minimize power consumption. TX should be tristated before entering sleep. This is due to the
sharing of PDI_DATA and TX. PDI_DATA has a pulldown active, which will consume current when TX
is set to output high. All three pins can be disconnected from the USB AVR using the solder jumpers.
MicroSD Card
The MicroSD card slot has a spring-loaded mechanism that locks the card in place when
inserted (push-in, push-out). The contacts are gold-plated. It is connected to SPI E using four pins. All
pins have external 47Kohm pullups installed. All four pins can be disconnected from the MicroSD card
slot using the solder jumpers. Note that when in the deepest sleep modes and a card is installed, it will
likely consume the most current. Since the minimum load required by the regulator is 100uA, and the
rest of the onboard components may consume less than 75uA, having a card installed may allow
disconnection of the minimum load resistor (solder jumper), which itself consumes 100uA.
32KB SPI SRAM
The 32KB SPI SRAM is the 23K256-I/SN from Microchip. It has a very simple protocol, and
can be quite fast operating at 16MHz with sequential access (ie: data capture). It is less suitable for
storage that requires random access. It is connected to SPI D using four pins, all of which have
47Kohm external pull resistors. All four pins can be disconnected using the solder jumpers. A simple
driver is provided in the ASF template. More more information, consult the datasheet.
RS-232 / RS-485
The MT-X1S comes with either an RS-232 or RS-485 interface IC installed. There are two
different PCB footprints, but the screw terminals and I/O lines are shared. Therefore, only one can be
installed on the PCB at a time. The RS-232 IC is the MAX3221IPWR from Texas Instruments. The
RS-485 IC is the ISL3175EIUZ from Intersil. The IC is connected to USART E via four pins. They are
RX, TX, RX enable, and TX enable. There are three 47Kohm pull resistors installed, a pullup on TX,
and pull resistors on the enable lines that keep both disabled by default. All four pins can be
January 29, 2015 12 http://www.mattairtech.com/