User's Manual

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Advanced Information
RN52-DS
2.2 LED Interface
The RN52 includes two pads dedicated to driving the
LED indicators. The firmware can control both termi-
nals, and the battery charger can set LED0. The termi-
nals are open-drain outputs; therefore, the LED must
be connected from a positive supply rail to the pad in
series with a current limiting resistor. You should oper-
ate the LED pad (LED0 or LED1 pins) with a pad volt-
age below 0.5 V. In this case, the pad can be thought of
as a resistor, RON. The resistance—together with the
external series resistor—sets the current, I
LED
, in the
LED. The current is also dependent on the external
voltage, VDD, as shown in Figure 2-3.
FIGURE 2-3: LED INTERFACE
The LEDs can be used to indicate the module’s con-
nection status. Ta b l e 2 - 1 describes the LED functions.
2.3 Device Firmware Updates
The module has a device firmware update (DFU) mode
in which you use the USB interface to update the firm-
ware. ImplementingImplementing the DFU feature is
recommended highly because firmware updates offer
new features and enhance the module’s functionality.
Follow the reference design shown in Figure 2-7 to
support this mode.
FIGURE 2-4: USB DFU PORT & GPIO3
SCHEMATIC
2.4 Restore Factory Defaults with
GPIO4
You should connect the GPIO4 pin to a switch, jumper,
or resistor so it can be accessed. You can use this pin
to reset the module to its factory default settings, which
is critical in situations where the module has been mis-
configured. To reset the module to the factory defaults,
GPIO4 should be high on power-up and then toggle
low, high, low, high with a 1 second wait between the
transitions.
TABLE 2-1: STATUS LED FUNCTIONS
Blue LED Red LED Description
Flashing Flashing The RN52 module is discover-
able.
Off Flashing The module is connected.
Flashing Off The module is connectable.
VDD
LED Forward
Voltage, V
F
Resistor Voltage
Drop, V
R
Pad Voltage, V
PAD
R
LED
|
LED
LED0 or
LED1
R
ON
= 20 Ω
Note: A 47 KΩ pull-down resistor (R2 in
Figure 2-4) is required on GPIO3 even if
you do not use the USB for DFU.
GND
5
D+
3
D-
2
VBUS
1
MTAB
6
J2
VBUS
(3.3V)
USBD-
USBD+
47k
R2
22k
R1
GPIO3
MBR120
D1
10nF
C4
USB Mini B Connector
(JAE DX2R005HN2E700)