9.4.1. Serial Port Usage
9.4.1.1. Primary Port Usage
TX: NMEA message output.
RX: NMEA proprietary commands, RTCM SC-104 (DGPS) input, EPO data.
TX/RX: Re-flash the module (SL869-V2 and SL869L-V2 only).
9.4.1.2. Secondary Port Usage
TX1/SDA: NMEA message output.
RX1/SCL: This port accepts DGPS input using the RTCM SC-104 protocol or NMEA
commands. Input is selected via the $PMTK250 command.
9.4.2. 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 the interface lines is logic high.
The input and output levels are LVTTL compatible. Please refer to Table 27: Logic Levels:
TX and 1PPS and Table 26: Input Logic Levels.
Note: RX pins have a maximum input voltage of 3.4 V (which is lower
than the maximum for Vcc or Vbatt).
Note: Care must be used to prevent backdriving the RX line(s) when
the module is powered down or in a low-power state.
9.4.3. I2C Port Operation (SL869L-V2 only)
The SL869-V2, SL869-V2S and SL869L-V2S do not support I
2
C interface.
The I2C_Clock and I2C_Data lines require external pullups (example value: 10 KΩ).
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