Roving Networks RN-374 Manual do Utilizador descarregar pdf (Página 20)

Advanced User Manual

www.rovingnetworks.com

rn-bluetooth-um Version 4.77 11/21/2009

809 University Avenue • Los Gatos, CA 95032 • Tel (408) 395-6539 • info@RovingNetworks.com

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Design Concerns

7.1 Hardware Signals

1. RESET circuit. RN-41 contains a 1k pullup to VCC, the polarity of reset on the RN41 is ACTIVE LOW.

RN21/22 contain a 1k pulldown, and the reset polarity is ACTIVE HIGH.

A power on reset circuit with delay is OPTIONAL on the reset pin of the module. It should only be required

if the input power supply has a very slow ramp, or tends to bounce or have instability on power up. Often a

microcontroller or embedded CPU IO is available to generate reset once power is stable. If not, there are

many low cost power supervisor chips available, such as MCP810T, MCP102/121, and Torex XC61F.

2. Factory reset PIO4. It is a good idea to connect this pin to a switch, or jumper, or resistor, so it can be

accessed. This pin can be used to reset the module to FACTORY DEFAULTS and is often critical in

situations where the module has been mis-configured.

3. CONNECTION status. PIO5 is available to drive an LED, and blinks at various speeds to indicate status.

PIO2 is an output which directly reflects the connection state, it goes HIGH when connected, and LOW

otherwise.

4. Using SPI bus for flash upgrade. While not required, this bus is very useful for configuring advanced

parameters of the Bluetooth modules, and is required for upgrading the firmware on modules. The suggested

ref-design shows a 6pin header which can be implemented to gain access to this bus. A minimum-mode

version could just use the SPI signals (4pins) and pickup ground and VCC from elsewhere on the design.

7.2 Hardware Connections and Power

Placing 3.3Vdc into the PIO’s while they are set as outputs will permanently damage the radio

modules. The failure mode is short across GND and VCC. Use a 10KΩ resistor in series or a 10KΩ

pull up resistor for input and output PIO’s respectively.

• Make sure to connect a common ground when using the external TX, RX inputs 0 – 3.3Vdc.

• For a 3 wire DB-9 interface (tx, rx, gnd only) connect/short CTS to RTS, Factory default is hardware

flow control enabled CTS and RTS connected.

• When using a 5.0Vdc Input, PIO’s require a voltage divider. A good choice is 10K ohm series with

20K to Ground. PIO’s are 0-3.3Vdc not 5 volt tolerant.

Hardware Communications Connections for Modules and Eval Board

Radio TX 



 RX of the application Micro Controller Unit (MCU)

Radio RX 



 TX of the application Micro Controller Unit (MCU)

Radio RTS 



 CTS of the application Micro Controller Unit (MCU)

Radio CTS 



 RTS of the application Micro Controller Unit (MCU)

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