User's Manual

Hardware Interfaces
A DIVISION OF TRIMBLE
Hardware Overview 27
TTL Level UART Interface
A level converter is necessary to interface to other devices that use standard 12V RS232.
Only three pins are required for serial communication (TX, RX, and GND). Hardware
handshaking is not supported.
The connected host processor’s receiver must have the capability to receive up to 256
bytes of data at a time without overflowing.
Baud rates supported:
– 9600
– 19200
– 38400
– 115200
– 230400
– 460800
– 921600
Note
Upon initial power up, the default baud rate of 115200 will be used. If that
baud rate is changed and saved in the application mode, the new saved
baud rate will be used the next time the module is powered up.
General Purpose Input/Output (GPIO)
The four GPIO connections, provided through the ThingMagic Nano Digital Connector
Signal Definition, may be configured as inputs or outputs using the MercuryAPI. The GPIO
pins should connect through 1 kOhm resistors to the module to ensure the input Voltage
limits are maintained even if the module is shut off.
Module power consumption can be adversely affected by incorrect GPIO configuration.
Similarly, the power consumption of external equipment connected to the GPIOs can also
be adversely affected. The following instructions will yield specification compliant
operation.
On power up, the ThingMagic Nano module configures its GPIOs as inputs to avoid
contention from user equipment that may be driving those lines. The input configuration is
a 3.3 volt logic CMOS input and is internally pulled down with a resistance value of
between 20 and 60 kOhms (40 kOhms nominal).
GPIOs may be reconfigured individually after power up to become outputs. Lines
configured as outputs consume no excess power if the output is left open.