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Bluetooth Breakout board Part 1

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Introduction

I recently purchased a RN42 bluetooth module from Sparkfun Electronics, this compact module measuring 14x25mm is designed for SMD assembly into a larger board, since I wanted to easily attach a 10 way connector to the board I developed this design which connects all relevant pins to a single 10W connector. It also has a 4×2 header strip to allow placement of the four jumpers to configure the module.

Jumper settings are

Default -> Place jumper to force the module to enter the manufacturers default configuration.

Auto -> Set the module to automatically discover any bluetooth devices within range (less than 10m) from the unit

Baud -> Fix Baud rate at 9600bps, the alternative is user configurable baud rate settings.

MSTR -> Set the module to master bluetooth mode.

Use of the module

 I used my Acer A500 Android tablet to connect to the module, I initially found it difficult to get the module to connect as by default the RN42 will not automatically pair with other bluetooth devices.

I have found that the S2 BT Terminal application works very well from the Google Play store.

I would suggest start by testing the module for basic comms this can be done using a loop back configuration. In this mode the TXD&RXD pins and RTS&CTS pins are shorted together. For the power supply I used the STK500 development board from Atmel but you can you any regulated DC power supply. Refer to the schematic in the downloads selection for help.

Once the module is configured for loop back configure the tablet/PC using what ever terminal emulation software you choose to use to use to connect to the module.

Assuming you are using the S2 BT terminal application

1. Apply power to the board, place no jumpers. The onboard LED should start flashing at approximately 1Hz rate. After a while the flash speed will show down to approx 0.5Hz once the module has undergone it’s internal power up sequence.

2. Start S2 BT terminal select settings from the toolbar at the bottom then connect device.

3. Select the RN42 from the list and connect to it, the LED should stop flashing and change to a soild lit.

4. Type some random text into the input box the same text should echo back once you press ASCII send.

Assuming the above stages work without any problems, you are now ready to connect a micrcontroller or PC via a MAX232 level shifter or similar. In a latter post I will explain how to write Android applications to write directly to the serial port.

 Figure 1: Top view of the module note the header for connection to a 5×2 way IDC connector and the 4×2 header for jumpers to configure the module. The LED is continuously lit once a connection has been established.

 

Figure 2: Bottom of PCB, bluetooth module has plating down the side of the PCB making surface mount soldering reasonably straight forward.

Downloads

PCB top overlay

PCB top copper

PCB bottom copper

Connection schematic


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