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Bluetooth ATB-BTM-222

The module ATB-BTM-222 version 2.0 – double-voltage - ( +3,3V / +5V ) in our offer is an excellent support for many projects with which you are going to face every day. Because the module works in Class 1 standard, it has up to 100 m range what is a big advantage in this case. Anyone who used Class2 standard modules just once (range only to 10m , e.g. BTM112) will never use it again because of their limitations. ATB-BTM-222 is based on a popular module BTM-222 from Rayson company. Because it is hard to solder it to own system in an amateur conditions we decided to prepared a specially dedicated small PCB board, and the board project was carefully thought out. As it often happens the power lies in a simplicity. So our module is designed to work with microprocessor systems powered by +5V. Also proper conversion is assured of TTL signals to +3,3,V because the BTM-222 can only be powered by +3,3V. On the PCB board we will fin LDO stabilizer, LM1117-3,3 symbol, with very fast power supply filtration. It is so underappreciated by the beginners that just start to use the modules that it cause many misunderstanding and irregularities on operation. Incorrectly designed power supply to this module may cause its hang up during transmission. That is way in competitive products you will find a RESET pin outside the module and a annotation that it can be used in case of module hang up during operation. It sound like this hanging up would be a normal thing predicted by a manufacturer. How abstruse this explanation are. In our module there is no pin RESET from the BTM-222 module because it is absolutely unnecessary to use it during normal operation. We guarantee that firmly with the possibility for you to turn the module back and we refund your purchase costs if something like this would happened. Voltage conversion in our module is assured by 74LVC125 integrated circuit. It ensures trouble-free transmissions UART to a max. values provided in a catalogue note of the BTM-222 module. Another often unappreciated advantage of our module is absolutely simple but thought out a connection interface. These are only four pins.

Selection of operation voltage +5V/+3.3V using a jumper


We used here a key (space) between them and such signal allocation which ensures that in case of accidental and incorrect connection the module will not be damaged what unfortunately happens in competitive products as we know from our customers’ information. Very often new customers before they buy our module they ask a question like: 

"Why you modules doesn’t have signals RTS, CTS and RESET pins from the BTM-222 module although the circuit is equipped in them and other, competitive products have these signals pins on edge connectors."

According to the RESET signal - I already wrote above and now few words about RS232 lines as: RTS and CTS. In fact the BTM-222 module has not only these signal pins but also many more as e.g. outputs for adudip PCM transfer, USN input (D+ and D-) and also some others what can be seen in the PDF catalogue note. Unfortunately a sad information is that each one of them - I stress – each one is not for use in this module version that is on the market sold by Rayson company. Why is that and what's behind all this? Namely – there are such a possibilities in these modules but on potentially because the company reserves that their use is possible only when a customer will additionally buy from the Rayson company a SDK developer kit, that lets you to write your own application for a microcontroller from inside the modules and which have by default only basic Bluetooth stack programmed limited to the SPP interface (Serial Port Programming). Another bad news is the SDK kit costs about 4000$. These are official information got from the Rayson company. Unfortunately, competitive BTM-222 modules manufacturers are not aware of many aspects that were described above and hence such interesting details in constructions which customers will never be able to use.


But there is also good news. For most purposes these additional signals are not necessary and despite it if we have only Rx and Tx signals regarding RS232 we are able to fins hundreds of interesting applications for these modules. It is also worth to know how to start configuration using AT commands and it was described widely in our book: "AVR microcontrollers, C language, Basics of Programming”. Thanks to the information included in the book you will find out how to configure the BTM-222 module fast and easy so it will be able to replace common RS232. Our modules are equipped with two basic LEDs. The blue one informs us up to date about Bluetooth connection state. The second red or green one informs us about proper power supply voltage for the module. The blue LED is especially important as its permanent light means that the Bluetooth connection is correct. It is particularly important when we meet the modules for the first time. Below I present several basic and the most important rules you should follow starting work with these modules, and also what you should not do.  

PDF application note - BTM-222 module




  1.  The BTM-222 modules in 99% of cases we use in applications in a SLAVE mode and not Master!
  2. The module configuration so e.g. baud rate speed setting, module name in BT environment, pin determining to devices pairing etc, we perform ONLY at the beginning using physical RS232 interface (Rx and Tx pins) and using a terminal (Windows/Linux).
  3. Do not ever do this configuration from the microcontroller level to which you are connecting the module and particularly at every restart because you can damage EEPROM memory in the module.
  4. To improve the communication maximally and to change practically in 100% the Bluetooth radio connection into equivalent common RS232 cable you should:
  • Turn echo off ( ATE0 )
  • Turn off AT answers from the module ( ATQ1 )



That is all. You can for that use any USB/RS232 adapter in TTL standard e.g. the one built-in every ATB start-up kit. After configuration the module stores the settings in its memory EEPROM permanently and we do not need to refresh every time we start the microcontroller. From now you can use radio connection as a common RS232 cable with any speed and making full use of two-way data exchange if necessary.




Examples of ATB-BTM-222 modules use are very wide so I will present only a few of them, the most important ones which I hope will inspire everyone to follow own ideas.



  1. An ability to remotely (via radio) charge a batch to microcontroller using the Bootloader. It probably the most commonly used option by me but not only by me. We do not have to open any housing of the device which sometimes is hard to get in or is under high voltage or is mobile. This option works unmistakably with our software "MkBootloader". You can test everything in a demo version of the program.
  2. Testing and debugging own project remotely using common terminal and at the same time without using RS232.
  3. Communication of any device/controller with a PC. Thanks to it you can not only present data processed by the controller but also make advanced configuration.
  4. Remote control from mobile devices such as tablets, mobile phones or PCs.



The possibilities mentioned above and many more provide a very high potential of possible use of the BTM modules and taking into account a standard of implementation by our company, we are dealing with a really reliable solutions that we can use even in industrial environments.

Dimension of the module: 41,65 mm x 25,24 mm x 6,46 mm ( length x wide x high)



The ATB-BTM-222 module, its connector you can find in a Eagle software library which we prepared especially for our customers. External connector in a raster 2,54 mm (5 pins):





ATB-BTM-222 modules available in our ONLINE STORE

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