Datasheet
2014 Microchip Technology Inc. DS70005171A-page 9
RN171
2.0 CIRCUIT DESCRIPTION
(HARDWARE INTERFACE)
The following sections describe the module’s hardware
interface.
2.1 UART Interface
The UART interface supports 2-wire (RX, TX) and 4-
wire configurations with hardware flow control (RX, TX,
CTS, and RTS). The logic levels are CMOS voltage
levels (not RS-232 voltage levels). The UART interface
supports baud rates of 2,400; 4,800; 9,600; 19,200;
38,400; 115,200; and 230,400 bits per second. Refer to
the “WiFly Command Reference, Advanced Features
and Applications User's Guide” (DS50002230) for
UART configuration information.
2.2 SPI Master Interface
The RN171 module contains a master SPI interface
(SPI_CS, SPI_CLK, SPI_MISO, and SPI_MOSI) that is
connected to an internal Flash memory. Do not connect
these pins on the host PCB.
2.3 SDIO Client Interface
The RN171 modules contain an SDIO client with SD-
SPI mode and interface (SD_CLK/SCLK, SD_D3/SS,
SD-D2, SD_D1/INT, SD_D0/MISO, and SD_CMD/
MOSI). This interface is not currently implemented in
the WiFly command reference.
2.4 In-System Programming (ISP)
The ISP_TX, ISP_RX, and other pins allow in-system
programming of the module. The module’s firmware
can be upgraded via ISP using a *.bin file.
Though it is optional, it is recommended to place the
ISP header on the host PCB to facilitate firmware
upgrades during development and manufacturing. The
header is two row by 8-pin with 0.050 inch space and
pitch (Samtech P/N FTSH-108-01-F-DV-K). Refer to
Figure 3-3 for information about connecting to the mod-
ule for ISP. The RN-ISP in-system programming inter-
face connects to the module for ISP. Refer to the RN-
ISP product page on the Microchip web site for more
information.
2.5 Analog Sensor Interface
Sensors (0-3) can be used to wake the module. The
sensor pins are 1.2V tolerant. When sensor pins are
used as sensor inputs, they accept input voltages up to
1.2V but saturate at 400 mV.
The 14-bit ADC requires a 35 ms conversion time with
0.01% linearity.
Additionally, the module has a low-power interface for
interfacing sensors such as push buttons, accelerome-
ters, security seals, and motion sensors.
2.6 Sensor Interface
The sensor can interface to:
• Four switch sensors
• A motion sensor for use with external ball-in-tube
• A pulsed comparator
• A Sample Measurement Unit (SMU) ADC
• A current generator for measurement
The switch sensors, motion sensors, and pulsed com-
parator are available when the module is awake or
asleep. The SMU ADC is only available when the mod-
ule is awake. The sensor elements share the module’s
eight sensor pins.
When the module is asleep, the sensor interface can
be used to detect events such as a switch opening or
closing, motion, or an analog voltage moving outside of
a preset window. When the module is awake, the SMU
can digitize the analog signals and make high-precision
analog measurements.
2.7 General Purpose Input/Output
(GPIO) Pins
The RN171 has 14 GPIO (GPIO1 through GPIO14)
pins that can be commanded by ASCII commands.
GPIO10 through GPIO14 pins have secondary func-
tions for the UART (TX, RX, CTS, and RTS), while oth-
ers can control connection modes, LEDs, etc.
Refer to the “WiFly Command Reference, Advanced
Features and Applications User's Guide”
(DS50002230) for information on configuring and con-
trolling the module.
Note: Use hardware flow control for baud rates
of 115,200 and higher.
Note: The over-the-air FTP update image file
(*.img) is not compatible with the ISP.
WARNING
DO NOT apply voltages greater than 1.2V on any
of the sensor pins.