WT12 Breakout

New WT12 Breakout

Full access to all of the pins of the WT12 Class 2 Bluetooth module from Bluegiga, now part of Silicon Labs.

Breakout Features

  • 1.5 in x 0.9 in PCB dimensions
  • PCB layout in accordance with datasheet recommendations
  • All module pins broken out (multi-pin VDD and GND nets combined)
  • Standard 0.1" pin spacing, aligned for easy breadboard mounting
  • Convenient board-end 3.3v UART interface header
  • Module reset button
  • Green power LED (solder jumper to disable)
  • Blue active-high user LED to PIO5 (solder jumper to disable)
  • Preloaded with latest available standard iWRAP5.5 firmware build (open-source parser here)

Development Resources

The breakout board itself does not currently have separate documentation other than what you see on this page, due mainly to its simple design. However, the WT12 module has many resources available. Some of the most relevant and useful may be found in the list below. To get started quickly with the WT12, you should have the following:

  1. 3.3V UART interface, either to a microcontroller or (for quicker experimenting) a USB-to-UART bridge like this FTDI breakout from SparkFun
  2. Latest Bluetooth Smart Software Development Kit release from Bluegiga, found in the Software Releases section of Bluegiga's WT12 product page

These links should help you get started:

Also, for those of you looking to use this with an Arduino or similar prototyping environment, check out the iWRAP parser code library and examples for Arduino and other platforms:

Module Overview

Description from Bluegiga.com WT12 product page:

The WT12 is a fully integrated Bluetooth 2.1 + EDR, class 2 module combining antenna, Bluetooth radio, and an on-board iWRAP Bluetooth stack. Bluegiga's WT12 constitutes the ideal solution for developers that want to quickly integrate Bluetooth wireless technology into their design without investing several months in Bluetooth radio and stack development. It uses Bluegiga's iWRAP Bluetooth stack, which is an embedded Bluetooth stack implementing 13 different Bluetooth profiles and Apple iAP connectivity. The WT12 combined with iWRAP Bluetooth stack and Bluegiga's excellent technical support designers ensure quick time-to-market and low development costs and risks.

Preloaded Firmware

These modules come with the latest standard iWRAP5.5 firmware image flashed on them. All settings are factory defaults except for two modifications which improve the accessibility of the breakout design itself:

  • SET BT NAME WT12 Breakout to make the board more obvious in a Bluetooth discovery process
  • SET CONTROL CD 20 0 to cause the blue LED to illuminate when there is an active connection

iWRAP provides an AT-style command interface for configuration and connection management. For details, please refer to the iWRAP User Guide and any relevant profile-specific application notes, which you can download from the module's product page. The UART interface is configured for 115200 baud, 8/N/1 with RTS/CTS flow control enabled. If you do not have flow control support on a host microcontroller, you can effect a hardware bypass by pulling the module's CTS pin to GND and leaving RTS disconnected.

You will not be able to use any iPhone or iPad device to discover or connect to this module with its default settings, due to the fact that iOS intentionally does not support the Serial Port Profile (SPP). The module can be easily configured to support iOS-compatible profiles like HID or PBAP with simple commands. The Apple-specific iPod Accessory Profile (iAP) requires a firmware update, which itself requires and active MFi program membership. Please contact Bluegiga for more information about this.

Updating Firmware

Although you will most likely be able to do everything you need to with the preflashed standard iWRAP firmware image, the firmware may be upgraded over the UART interface using Bluegiga's SerialDFU application for Windows, or certain SPI-based updated tools from CSR (part of BlueFlash, which is also available from the WT12 downloads area). All available firmware images and update tools are included in the main iWRAP Firmware Release Archive which you can get from the downloads area. Firmware providing restricted functionality like the Apple's iAP profile must be requested directly from the Bluegiga support team.

Bare PCB Assembly

Building this by hand is not an easy task. If you are not comfortable with SMT modules and reflow/hot-air rework, you should probably get the assembled board instead of the PCB alone. However, with a solder stencil and a steady hand, it is not too difficult. Further, you can benefit from the breakout design even if you only mount the module itself on the board. All other components are not strictly required for core functionality.

To obtain a solder stencil, download the stencil Gerber file (*.tcream layer) and use the tool or service of your choice to create a stencil. OSH Stencils provides excellent value, for example. You can buy the WT12-A module from SemiconductorStore or Mouser for about $16. It is available through other distributors as well; be sure to compare sources to find the best price. The discrepancy is sometimes quite large between different distributors. You can choose any part variant as long as it starts with WT12-A. The part number suffix indicates the firmware configuration, which may be updated via UART as described above. It is not difficult to order an early firmware version and then upgrade after assembly.

A shared Mouser project with single-board quantities of all parts for the current version 3.0 of the breakout is also available to help you get started.

Bluetooth Compatibility

The WT12 is a Bluetooth 3.0 BR+EDR device, also known colloquially as Bluetooth classic. It is not compatible with new Bluetooth Low Energy (BLE) devices, although it can communicate with Bluetooth Smart Ready devices, which support both classic Bluetooth and BLE. With appropriate profiles configured within the iWRAP firmware, you can use this module to communicate with most PC/Mac/Linux computers, smartphones, tablets, and almost anything else supporting standard classic Bluetooth. Note that wireless iOS device communication with Apple's iAP profile is supported only with a custom firmware update from Bluegiga, and an additional component available through Apple's MFi store.

Technology Bluetooth Classic (3.0)
Output power +4 dBm maximum
Antenna On-module ceramic chip

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Tags: wt12, bluegiga, silabs, bluetooth, breakout