Digi XBee 3 Cellular LTE-M, User Manual, Page: 106 / 331

Hardware XBee header connector requirements
Digi XBee® 3 Cellular LTE-M/NB-IoT Global Smart Modem User Guide 106
Pin Name Direction Default Description
17
AD3 / DIO3 / SPI_
SS / CTS2
Either Disabled
Analog Input 3 / Digital I/O 3 / SPI low
enabled select line / Clear to Send (CTS2)
Input
See the
secondary UART note below for more
information.
18 AD2 / DIO2 / SPI_
CLK / RTS2 Either Disabled
Analog Input 2 or Digital I/O 2, SPI Clock line /
Ready to Receive (RTS2) Output
See the
secondary UART note below for more
information.
19
AD1 / DIO1 / SPI_
ATTN / I2C_SCL
Either Disabled
Analog Input 1 or Digital I/O 1, SPI Attention
line output / I2C SCL
See the
I2C note below for more information
20 AD0 / DIO0 Either Input Analog Input 0, Digital I/O 0
Note Secondary UART : TX2, RX2, RTS2, and CTS2 (pins 4, 11, 18, and 17) may optionally be configured
as a secondary UART serial port using MicroPython. See Class UART in the Digi MicroPython
Programming Guide and for details.
Note Class I2C : For more information, see Class I2C in the Digi MicroPython Programming Guide .
Pin connection recommendations
To ensure compatibility with future updates, make USB D+ and D- (pin 7 and pin 8) available in your
design.
The recommended minimum pin connections are VCC, GND, DIN, DOUT, RTS, DTR and RESET.
Firmware updates require access to these pins.
XBee header connector requirements
The XBee header connectors require the following attributes:
n
female
n
2 mm pitch
n
10 positions
n
single row
RSSI PWM
The XBee Smart Modem features an RSSI/PWM pin (pin 6) that, if enabled, adjusts the PWM output to
indicate the signal strength of the cellular connection. Use
P0 (DIO10/PWM0 Configuration) to enable
the RSSI pulse width modulation (PWM) output on the pin. If P0 is set to 1, the RSSI/PWM pin outputs a
PWM signal where the frequency is adjusted based on the received signal strength of the cellular
connection.
The RSSI/PWM output is enabled continuously unlike other XBee products where the output is enabled
for a short period of time after each received transmission. If running on the XBIB development board,
DIO10 is connected to the RSSI LEDs, which may be interpreted as follows: