Connecting bluetooth audio module spk 8635 b. Bluetooth module for audio transmission

Today I’ll tell you about the XS3868 audio module assembled on Bluetooth chip OVC3860 working with profiles A2DP v1.2 (audi transmission) and AVRCP v1.4 (control any bluetooth device such as mobiletelephone, bluetooth adapter etc).

Technical parameters of XS3868

Supply voltage: DC 3.6v - 4.2v
Maximum working current: 55mA (standby 10mA)
Bluetooth version: 2.0
Frequency: 2.402 - 2.480 GHz
Maximum transmitter power: Class 2, 4 dBm
Receiver sensitivity: -82 dBm
Range: Approximately 10m
Data transfer rate: up to 3 Mbps
Built-in headphone amplifier: 40mW
Power saving mode transition time: 5 minutes
UART connection speed: 115200 baud
Built-in stereo DAC: 20 bit
Built-in mono ADC: 16 bit
Built-in battery charge controller: Li-ion, Li-Pol
Battery charging current: up to 150 mA
Connection password: 0000
Dimensions: 30 x 17 x 4mm

General information

The XS3868 module is designed for soldering on a printed circuit board, the contact pitch is 1.3 mm (by the way, the module has small dimensions of only 30 mm by 17 mm), assembled on the OVC3860 chip, which is Bluetooth transceiver with low power consumption, only 55 mA in playback mode and 10 mA in standby mode. The chip operates at a frequency of 2.4 GHz, and Bluetooth v2 + EDR (improved bluetooth version v2, increased data transfer rate), which allows you to transmit good sound (20 bits), you can also use the module to control the volume, stop tracks and switch them, and of course, make calls.

The module has a green mask and all electronic components are located on the same side of the PCB. On the upper part there is an antenna with a place for soldering an external antenna, in the center there is an OVC3860 Bluetooth chip with a minimum electronic piping (capacitors and resistors, quartz). On the left is a 4XK6 LDO regulator in a SOT23-5 package, and to the right is another 4XY6 regulator (XC9235E26DM) assembled in exactly the same SOT23-5 package. A T24C08A memory chip is provided to store the configuration. On the reverse side printed circuit board, there are no components. The location and assignment of the pins is shown in the figure below.

Pin assignment:
1 (AOM) - audio output "GND"
2 (AOL) - audio output "Left"
3 (AOR) - audio output "Right"
4 (MIC+) - microphones (+)
5 (MICBIAS) - microphone (-)
6 (LED1) - LED connection
7 (LED2) - LED connection
8 (VCC) - 5V power supply (for battery charging)
9 (GND) - power GND
10 (VBUSK)
11 (VBAT) - battery (+)
12 (1V8) - output 1.8V
13 (RESET) - reset
14 (ONKEY) - PLAY / PAUSE button
15 (VOL +) - volume up button
16 (VOL-) - volume down button
17 (MFB1)
18 (UART_TX) - UART interface
19 (UART_RX) - UART interface
20 (MODE)
21 (NEXT) - NEXT button
22 (PREV) - PREV button
23 (MUTE) - silence button

The easiest way to connect XS3868, this will use a special adapter, which already has built-in buttons, indicator lights and a battery for battery life, but there are also disadvantages, the cost increases. There is a second way to turn on, with a minimum connection of wires. To do this, you need to connect power, a 4.7 kOhm - 10 kOhm resistor between the 1.8V OUT and RST terminals and an audio connector (if you connect passive speakers, without an amplifier, you need to add an amplifier to the circuit). We assemble the schematic diagram, which is shown in the figure.

In the example, I am finalizing the Logitech Z240 speakers. On the back wall there is a transformer with a variable output voltage of 9V, the voltage is rectified on the board (by the way, I have active speakers with a built-in amplifier). Since the board uses a voltage of 9V, it is necessary to use an LM2596 voltage converter (there is little interference) with a voltage set to 3.7. We connect the input of the LM2596 module to the volume control so that when the amplifier is turned off, the XS3868 (because after 5 minutes the audio module will turn off) and the LM2576 output is connected to the XS3868 audio module, according to the diagram above.

Note: In general, it all depends on the circuitry, you can find a built-in stabilizer (a multimeter to help) or not find them at all (if a passive speaker), there is also a little interference (noise and crackling), this is due to the general power supply of the amplifier and Bluetooth, to get rid of it, you need to use an isolated dc-dc converter, as well as use ferrite cores, as they come, I will finalize it.

Now, when the speaker is turned on, a melodious melody will play, the volume will automatically be at maximum (of course, if the XS3868 is without an adapter). Next, we look for a new Bluetooth device on the phone with the name POR 1007BT, the password for connection is 0000. If the module is not used for 5 minutes, it goes into power saving mode (turns off), to return to working mode, you need to reset the power.

Audio module XS3868 based on OVC3860 (Bluetooth 2.0)
Adapter for XS3868

As an UMZCH, I used a stereo ULF of 20 watts per channel, which costs $ 20 on ebay. You need to disassemble it and inspect the inside of the case in order to understand where to get power from the module and where, in fact, to place it. When everything is unscrewed, the amplifier looks like this.

Now about the bluetooth audio transmitter. It is bought ready-made.

All together - adapter and stabilizer, costs less than 8 dollars.

The disassembled Bluetooth audio receiver is shown in the photo. Connect 3 wires to the audio jack.

Now solder the wires from the USB cigarette lighter - charger.

They are both designed for power supply from 12 V. If the amplifier works even from 24 V, it is still suitable. But if the amplifier is powered by a higher voltage or is powered directly from a 220 V network, you will have to take usb charger separately, or look for a reduced stabilized power supply on the board of the UMZCH itself. In general, deal with this yourself.

Now connect it to the bluetooth receiver according to the power on the board - this is 5 volts. Both modules are attached to an aluminum heatsink as the most massive element of the circuit.

The input wires are directly soldered to the line audio out of the amplifier, but if you want to add active subwoofer or connect something else like that, you need to drill a separate 3.5 mm output in the rear panel. Secure the bluetooth receiver itself with hot glue to a suitable place.

The other day came from the online store GearBest Bluetooth audio modules XS-3868 Ver.3.0 based on OVC3860. The modules are a device to which you can connect via Bluetooth and transmit the audio stream "over the air". The cost is approximately $3.5. The small size and power supply of the module, fully adapted to work from 3.7 volt Li-Ion batteries, allow, in my opinion, to integrate these modules into a huge number of their devices: this and homemade bluetooth headsets, and wireless and portable speakers, and a wireless interface for speakers and players, and some intercoms(unless, of course, the operating range suits), and everything else that a radio amateur's fantasy can reproduce.

Specifications of Bluetooth audio module XS-3868 based on OVC3860:

• Frequency 2.402 ~ 2.480 GHz
• Transmitter power 4 dBm (PCB antenna), Class2
• Receiver sensitivity -82 dBm
• Module size 30 x 17 x 3.4 mm
• Bluetooth: Version 2.0
• Range approx. 10 m
• Data transfer rate up to 3 Mbps
• Possibility to connect an external antenna via SMT platform
• Ability to connect a mono microphone
• Audio flow and volume control (buttons)
• Module operation indication by two LEDs
• Stereo audio output (Designed to connect headphones with 32 ohm speaker impedance - built-in 40mW headphone amplifier)
• Supply voltage 3.6 - 4.2 Volts
• Current consumption up to 55 mA in audio playback mode
• Current consumption in sleep mode is less than 10 mA (actually less than 1 mA)
• Time to enter power saving mode 5 min (when nothing is playing)
• Profiles: A2DP V1.2–Sink Only, AVRCP V1.4–Controller Only, HSP V1.2, HFP V1.5
• UART connection speed 115200 baud (used mainly for debugging)
• Built-in 20 bit stereo DAC
• Built-in 16 bit mono ADC
• Integrated charge controller Li-ion batteries, Li-Pol, charging current up to 150 mA
• Connection password 0000

The characteristics of the module copy the characteristics of the Bluetooth controller OVC3860.

The module has the following pinout:

Module pin assignment:

• 16, 17, 19 – stereo audio output (for headphones, not every audio system will pull, so when connected to some acoustic systems you will have to solder the preamplifier, unlike headphones, the 5.1 microlab system refused to work normally with this module when connected directly)
• 22, 23 - contacts for connecting a microphone (Bluetooth headset after all)
• 24, 26 - contacts for connecting LEDs
• 25 - 5 volt power input for battery charging
• 31 - earth
• 29 - battery plus
• 33 - output 1.8 volts
• 35 - contact reset
• 36, 37 - contacts of volume control buttons
• 43, 44 - UART interface
• 52, 54, 55 - contacts of audio stream control buttons

To start Bluetooth usage device does not need to do any complicated actions, you just need to connect the power (battery), a 4.7 kOhm - 10 kOhm resistor between the 1.8v out and rst pins and a headphone jack. By default, the module is visible to others Bluetooth devices like POR 1007BT. Connect, enter the password when prompted. The module is defined as a headset, and when connected, the sound will be transmitted already “over the air”. If you connect only power and headphones without module buttons, then the volume will automatically be at maximum. It all depends on the device to which the module is connected. So when adjusting the sound level on the tablet, the sound is also adjusted on this Bluetooth module, and when connected to a phone ( Philips xenium x130) the volume level simply remains at maximum or simply turns off no matter how you adjust the volume of the audio file.

Here the simplest circuit enabling the module:

Using a few more outputs of the Bluetooth module, you can make a slightly more functional device with buttons and LED operation indication, diagram:

And then, simply by adding a microphone, connecting it to the corresponding outputs of the Bluetooth module, using the appropriate microphone switching circuit, you can use the device as a full-fledged Bluetooth headset for talking on the phone, for example. By the way, you can estimate the dimensions of the parts and see that the dimensions of the device are no larger than many factory copies.

Although the module has the ability to charge a small battery, using this function here is not very beneficial: 1) nothing is played in the charging mode, 2) a small charging current, which means that only small batteries can be used, 3) switching to sound playback mode after charging requires additional action - either disconnect and connect the headphones, or press the reset button, which will have to be done, or simply distort the power. In my opinion, it would be better to additionally use a charging circuit for the battery, for example, based on TP4056:

The dimensions of such ready-made modules are small and they are smaller than the batteries themselves, even of a small capacity. So I think it's a little the best way than the built-in Bluetooth function of the module.

If you use such a module, you must observe two nuances: 1) you cannot turn on the charging module connected to the Bluetooth module without a battery, since the voltage without a battery at the output of the charging module can exceed 4.2 volts; 2) set the charging current for the used battery. The charging current is regulated by a resistor connected to the second pin of the TP4056 chip. By default, a 1.2 kΩ resistor is usually installed on charging modules, which corresponds to 1 A of charging current. 1.5 kOhm - 780 mA, 3 kOhm - 400 mA, 10 kOhm - 120 mA, 20 kOhm - 70 mA.

If you do not want to use the Bluetooth module as portable device with a battery, then instead of the battery it is necessary to make a power source of 3.7 - 4.2 volts, add capacitors to the power nodes in the circuit and use it as a stationary device.

Thus, for a small cost, you can get a DIY (do it yourself or do it yourself) kit for wireless audio transmission via Bluetooth.

Below you can download some documentation on the Bluetooth module. I hope this short review will be useful in finding solutions for amateur radio purposes.

I think many managed to grab at a discount bluetooth transmitter ORICO BTA-403, so it's time to talk about the receiver with support for this very aptX.
This module was originally purchased to replace the module in the car radio. But it was not possible to replace him. The money has already been paid, so you need to this module dispose of it in some other way.
The module is assembled on a CSR8645 chip. The chip is not the coolest in the line, but it has very good characteristics.

The module is really tiny 26 * 13 mm and almost weightless, it arrived without a track immediately in mailbox, I found a picture with a pinout on the Internet and hastily made just such a handkerchief.

This is the first, test sample, I was in a hurry and made a mistake when connecting the buttons. (They still did not work, except for the power button, so in the final version the board will be without buttons).
The device is defined as F-3188, pairing without a password, after turning it off and on, it does not automatically connect.
The pitch of the side contacts is 1.1 mm, in principle, a thin soldering iron can be soldered directly.
The amplifier has a balanced output and is designed to connect headphones (for example, QCY QY7 are assembled on the same chip) and has 4 pins R + R- and L + L- This somewhat complicates the connection to the amplifier, which often has three wires (the Chinese solve this problem simply - R - and L- are connected to the "ground" through a capacitor. This will not work with this module. With this connection, a background appears. I connected it to an amplifier on the pam8610, after some manipulations it has a balanced input, so they will play in a pair in the kitchen )
Insignificant current consumption allows you to power the module from a linear regulator 1117 at 3.3 volts without any tricks.
In standby mode, it was not possible to measure the current consumption - it is so insignificant
(once the device showed 3 microamps, then it just shows 0).
Connected

In playback mode.


The sound quality was tested by connecting the module to the analog input of the Pioneer VSX-524-K receiver and the Pioneer S-ES21TB acoustic kit.
The repertoire was played from usb, using the receiver's own DAC and through the module with Galaxy smartphone S5.
According to subjective sensations, the amount of high and low frequencies is reduced via Bluetooth, the sound becomes flatter, but overall it remains quite pleasant.
The output volume when connected to the receiver is not enough, you have to increase it.
Perhaps it could be added, but the buttons do not work.
When you turn off the sound or when you just pause the module, the module turns off and a low-frequency background appears.
It was possible to reduce it a little by installing a variable resistor.
It was not possible to establish the range of action, but I freely moved around the apartment with the phone, there were no sound fading and no disconnections.
In general, I liked the module, the sound is incomparable with cheaper modules, the downsides are broken buttons and the lack of intelligible documentation.