ThingMagic M5e-Compact - Manual (Page 49)

Serial Port
Functionality of the Embedded Modules 49
Serial Port
The modules communicate to a host processor via the TTL logic level UART serial port,
accessed on the 12-pin digital connector for M5e/M5e-Compact. See
M5e/M5e-Compact
Digital Connectors .
UART TTL Level TX
V-Low: Max 0.4 VDC
V-High: 2.9 to 3.3 VDC
8 mA max
UART TTL Level RX
V-Low: -0.3 to 0.8 VDC
V-High: 2 to 5.5 VDC
(Tied to 3.3 V through a pull-up resistor. Not harmful, but not recommended to drive
the input above 3.3 V because then the input will be sourcing current to the 3.3 V
supply.)
A level converter could be necessary to interface to other devices that use standard 12V
RS-232. Only three pins are required for serial communication (TX, RX, and GND).
Hardware handshaking is not supported. The serial port has an interrupt-driven FIFO that
empties into a circular buffer.
The developer is responsible for ensuring that the host processor’s receiver has the
capability to receive up to 256 bytes of data at a time without overflowing.
General Purpose Inputs/Outputs (GPIO)
The Mercury Embedded modules have four TTL level signals, two input lines and two
output lines, available on the 12-pin (M5e/M5e-Compact) digital connector. These can be
controlled via the Get User GPIO Inputs and Set User GPIO Outputs commands.
Note
If you are Using a Multiplexer the available GPIO Outputs will be reduced to 1
or 0 depending on whether one or both are used as control lines as specified
by
Set Reader Configuration(9Ah) .
For further information, see Get User GPIO Inputs (66h) and Set User GPIO Outputs (96h) .