SE868Kx-Ax Family Product User Guide
1VV0301201 Rev. 5
Page 51 of 83
2021-07-15
Not Subject to NDA
Serial I/O Ports
Port 0:
All modules include a primary UART serial port (TX0 / RX0).
Port 1:
The secondary port on
MT3333-based
modules is I
2
C by default, but can be changed to
UART (TX1/RX1) or SPI via command. The module will reset when the interface is
changed.
The secondary port on
MT3337-based
modules is UART (TX1 / RX1) and cannot be
changed.
Port Usage
9.7.1.
Primary (Port 0) Usage
TX0: NMEA message output
RX0: NMEA proprietary commands, RTCM SC-104 input and EPO data
TX0 / RX0 is also used to re-flash the module (
MT3333
-based modules only).
9.7.2.
Secondary (Port 1) Usage
TX1: NMEA message output.
RX1: DGPS input using the RTCM SC-104 protocol and NMEA commands.
I2C and SPI support the same data streams as UART.
The interface is selected via the $PMTK258 command.
Note that the module will reset when the interface is changed.
9.7.3.
UART Port Operation
UART ports are full-duplex and support configurable baud rates.
Frame is 8 bits, no parity bit, and 1 stop bit.
The default rate of 9600 bps can be changed via the following commands -
Primary port: $PMTK251
Secondary port: $PMTK250
The idle state of UART interface lines is logic high.
