BTM-222 Bluetooth Module. Overview, Schematics, PCB

1. BTM-222 main features

Btm-222 is a product of Rayson Technology Co. It is class1 module. This module was designed to replace the wire UART connection between two dev ices. It allows to organize wireless data receiving and transmition in a distance up to 100m (depends on connected antenna). Btm-222 is ready to use with the factory settings of UART which are as follows:

• Baud rate: 19200 bps
• Data bit: 8
• Parity: none
  
• Stop bit: 1

To organize the data exchange at least 2 devices are needed, one of these devices will function as Master and others as Slave. By defaults the role of module is set as Slave. It can be changed using AT commands. So, two the same BTM-222 modules can be used in pair Master-Slave. When two modules are in the signal area, the connection between them appears automatically (in case they have the same PIN, which can be changed using AT commands). If two modules are connected, the data sent to the UART interface of 1^st module will appear on the UART interface of another module.

Fig.1.1. Bluetooth module top view (uncovered/covered)

Short list of features:

• Bluetooth Ver. 2.0+EDR certification
• Transmit Power up to +18dBm(class1)
• Low current consumption: Hold, Sniff, Park, Deep sleep mode
• 3.0V to 3.6V operation
• Full Bluetooth Data rate over UART and USB
• § Support up to 7 ACL links and 3 SCO links
• Enhanced Data Rate(EDR) compliant for both 2Mbps and 3Mbps modulation modes
• Interface: USB, UART&PCM(for voice codec)
• SPP firmware with AT commands
• RoHS Compliant
  
• Small outline: 28.2 X 15.0 X 2.8 mm

2. AT Commands. Terminal

To send AT commands or data to the module a simple terminal can be used – standart windows terminal or, for example, “Terminal v 1.9 by Bray” (see Fig.2.1). All AT commands are described in the BTM-222 datasheet. You can change PIN, name of your device, baud rate , etc.

Fig.2.1. Terminal v.1.9b by Bray 

3. Schematics
Fig.3.1. BTM-222 schematics (connection to uC)

Fig.3.1 illustrates typical schematics of connection BTM-222 bluetooth module to microcontroller. As we know from BTM-222 datasheet, its operating voltage is 3.0V-3.6V. Most of microcontrollers need +5V to operate, this is why logic level converters (from 5V to 3.3V for BTM-222 and from 3.3V to 5V for uC) are used . If you use, for example, Atmega8L which can be supplied from 2.7V-5.5V then you can connect RX and TX directly.

4. PCB

DOWNLOAD PCB PRINT

On Fig.4.1 is demonstrated finished bluetooth module BTM-222 PCB. It was designed by me and I have to tell that it could be done much better, but it's tested and 100% working, so you can use PCB PRINT posted here to make one for yourself. The bill of materials is on Fig.4.2.

Download BILL of Materials

Fig.4.1. PCB top viewFig.4. Bill of materials

TO BE CONTINUED...