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Multiinterface Bluetooth Module
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Multiinterface Bluetooth Module
USB - RS232 - TTL

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Here is another recent project, which is not a stepper controller. It is a Bluetooth module with a decent number of connections available. The Class 1 module can be connected to an RS232 or USB interface. It's range is up to 100 meters. Besides the wireless connection via Bluetooth, it may also be used as a wired RS232 - USB converter. When using the module via USB, no additional power supply is necessary. Using the module in RS232 or TTL-mode requires a regulated power supply with a 5 V voltage, or a voltage range of 12-30 V. When using a 12 - 30 V power supply, a regulated 5V power supply is provided in addition by the module. The small footprint of 44*15 square millimeters allows for simple housing in conventional plug casings. The BTM-222 module from Rayson (www.rayson.com) provides the basic functionality. In addition, a simple Microsoft Windows compatible program for configuration is provided.


Soldering this module is no big issue, but one has to be aware that - given the actual size - SMD technology was used for print layout. However, all components are rather large besides the USB module. Given the intended application, not all components have to soldered to the print. Therefore I will try to give a description for building the Bluetooth module with respect to the intended application. Just stick to the description.

Click to enlarge

Click to enlarge

Components for the USB interface:

X2, IC2, R10, R11, C9, C6, C7, C8

Components for the RS232 interface:

X1, IC4, D2, C1, C2, C3, C4, C5

Components for the Bluetooth interface:

IC1, IC3, T1, T2, D1, LED1, R1, R2, R3, R4, R5, R6, R8, R9, C10, C11

Components for the 12 V power supply:

IC5, C12, C13

The power supply is to be soldered to plug X1. If plug X1 is not used, one may solder it directly to the pads. The two capacitors may be connected directly to the voltage regulation unit.

Click to enlarge

In dependence of the interface type chosen, some jumpers have to be connected by soldering. If the RS232 module is not required but the TTL supply is to be used, jumpers JP1 and JP2 have to be connected. If the 12 V power supply is to be realized, jumpers JP3 and JP4 have to be connected. If a 5 V power supply is necessary for the module chosen, or if you want to use the 5 V output in addition to the 12 V power supply, jumper JP5 is to be connected. If you have any questions, you may simply ask for support in the bulletin board Elektronik und Astronomie.

The Submini-D 9 plug was connected in such a manner that the module can be directly used with the LittleFoot Elegance Photo stepper controller. If all components are provided, a USB to RS232 converter for video processing and a Bluetooth interface to the stepper controller are available. Other uses of the module are, of course, feasible.

Wiring diagram of the Submini-D 9 plug:

1 RxIn (USB <-> RS232)
2 TxOut (Bluetooth)
3 RxIn (Bluetooth)
4 TxOut (USB <-> RS232)
6 +5V
7 +5V (voltage regulator)
8 GND (voltage regulator)
9 Vin (voltage regulator)


Depending on the hadware configuration of the module, it is to be connected to the RS232 or the USB interface of your PC. A small Microsoft Windows compatible program with a simple user interface is provided. After choosing the COM port, a connection is established and new parameters may be stored, or the given configration is read. In case of problems you may resort to our bulletin board: Forum.

Click to enlarge

Have fun

The published prints and instructions are free for personal use. Commercial use requires my written permission. Building the hardware is at your own risk. I cannot be held responsible for intended funtionality or any harm that may be caused by the electronic devices described here.
However, this stuff works in my case. However, I have no interest in being sued by clueless people who accidentially set their home on fire for some reason.

Copyright © 2009 by Anand Rajiva , E-Mail: anand@rajiva.de