User's Guide

ThingMagic M3e User Guide
11
www.JADAKtech.com
supported. This is a TTL interface; a level converter is necessary to connect to devices that use a 12V
RS232 interface.
The RX line is a 3.3-volt logic CMOS input and is internally pulled up with a resistance value of between 20
and 60 kΩ (40 kΩ nominal). It must be low before the module is turned off and low before the module is
turned on. This can be ensured if interface drivers are used that are powered by the module itself, as
shown in the interface board example.
The connected host processor’s receiver must have the capability to receive up to 256 bytes of data at a
time without overflowing.
These are the baud rates supported on the interface (bits per second):
• 9600
• 19200
• 38400
• 115200
• 230400
• 460800
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. (Check the firmware release notes to confirm that saving of settings is
supported.)
Recommended maximum receiver baud-rate errors for various character sizes are shown in the table
below.
Recommended Maximum Receiver Baud Rate Errors
Baud rate
Recommended max Rx error
Min (-2%)
Max (+2%)
9600
9412
9796
19200
18823
19592
38400 37647 39184
57600
56470
58775
115200 112941 117551
230400 225882 235102
460800
451765
470204
General Purpose Input/Output (GPIO)
M3e has 4 bi-directional GPIO Pins.
The four GPIO connections, provided through the ThingMagic M3e Digital Connector Signal Definition
,
may be configured as inputs or outputs using the MercuryAPI. The GPIO pins should connect through 1
kΩ resistors to the module to ensure the input Voltage limits are maintained even if the module is shut
off.
Module power consumption can be increased by incorrect GPIO configuration. Similarly, the power
consumption of external equipment connected to the GPIOs can also be adversely affected.