RN52 datasheet(14/26 Pages) MICROCHIP

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RN52

DS70005120A-page 14

 2015 Microchip Technology Inc.

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 0.5V. In this case, the pad can be thought of

as a resistor, RON. The resistance, together with the

external series resistor, sets the current, ILED, 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. Table 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

firmware. Implementing the DFU feature is highly rec-

ommended because firmware updates offer new fea-

tures 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 AND

GPIO3 SCHEMATIC

2.4

Restore Factory Defaults with

GPIO4

The GPIO4 pin should be connected to a switch,

jumper or resistor so it can be accessed. This pin is

used to reset the module to its factory default settings,

which is critical in situations where the module has

been misconfigured. 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.

2.5

Power Control and Regulation

The VDD pin controls the power to the RN52 module.

The VDD pin should be used to turn the RN52 module

on and off, if the hardware power cycle feature is

desired.

The PWREN pin provides the power enable functional-

ity. This pin is internally connected as an enable pin to

the voltage regulator and can only be used to turn on

the voltage regulator after VDD power is provided to the

RN52 module. The PWREN pin cannot be used to turn

the voltage regulator off.

On later versions of the firmware, the RN52 also pro-

vides a module reset GPIO pin, which resets the RN52

module when asserted high, and also provides a con-

sole command which can be used to perform a module

reset.

TABLE 2-1:

STATUS LED FUNCTIONS

Blue LED Red LED

Description

Flashing

Flashing The RN52 module is

discoverable.

Off

Flashing The module is connected.

Flashing

Off

The module is connectable.

Note:

A 47 K

 pull-down resistor (R2 in

Figure 2-4) is required on GPIO3 even if

you do not use the USB for DFU.

VDD

LED Forward

Voltage, V

Resistor Voltage

Drop, V

Pad Voltage, V

PAD

LED

LED0 or

LED1

ON = 20 Ω

GND

D+

D-

VBUS

MTAB

VBUS

(3.3V)

USBD-

USBD+

47k

22k

GPIO3

MBR120

10nF

USB Mini B Connector

(JAE DX2R005HN2E700)

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