FSC-FAQ

[中文]

Software Related

General

Why am I not receiving a response or error message from the module?

1. Check if the module is started normally, i.e., whether the mobile phone can search for the module and whether the LED pin of the module has an output signal. (The assignment of LED pins can be found in the datasheet)

2. Check if the UART configuration of the module is correct, such as the COM port number and baud rate of UART. Ensure that the AT command you send ends with “rn”.

3. Check if the module is connected to the mobile phone. In transparent transmission mode, the module is connected to the mobile phone, and data received from the host through UART will not be parsed as AT commands but will be directly sent to the mobile phone.

4. If the above measures still do not solve the problem, please use a logic analyzer or oscilloscope to capture UART Tx/Rx waveform data, or save the serial port logs on Feasycom serial Port.exe (check “Echo” before debugging), and send the serial port logs or waveform data logs to the Feasycom FAE team for analysis.

5. (Note: It is recommended to use Feasycom Serial Assistant.exe for debugging)

Where can I get the Bluetooth APP for testing?

1. Search for “FeasyBlue” in Google Play Store or iOS App Store to get the application. In addition, Feasycom can also provide FeasyBlue SDK for secondary development.

2. For more software and tools, please visit [FSC-APP] .

Why can’t I use FeasyBlue on my Android phone?

1. Turn on the Bluetooth of the phone

2. Grant all required permissions to FeasyBlue (Bluetooth and location access)

3. Enable high-precision location mode (Settings -> Privacy Protection -> Location Information -> Location Access)

Where can I find the test APP?

The latest Feasycom APPs and SDKs can be obtained at [FSC-APP] .

How to upgrade the firmware?

Currently, Feasycom modules mainly have three firmware upgrade methods operable by users:

UART upgrade, USB upgrade, over-the-air upgrade.

Modules supporting UART upgrade: FSC-BT802, FSC-BT816S, FSC-BT821, FSC-BT826, FSC-BT836, FSC-BT906, FSC-BT909, etc.

Modules supporting USB upgrade: FSC-BT802 (optional)

Modules supporting over-the-air upgrade: FSC-BT616, FSC-BT630, FSC-BT671, FSC-BT681, FSC-BT826, FSC-BT836, FSC-BT906, FSC-BT909, FSC-BT1026, etc.

(Note: If the module does not support over-the-air DFU, it is recommended to reserve upgrade pins during layout)

How to achieve reliable high-speed transmission?

Use a high UART baud rate,

Enable UART hardware flow control (RTS/CTS).

Use data checksum and retransmission mechanism.

What is transparent transmission mode?

In transparent transmission mode (TPMODE=1), the module enters the AT command state when disconnected and enters the transparent transmission state when connected.

After the module completes power-on initialization, it will automatically enter the AT command state, waiting for the host MCU to send AT commands. When the module establishes a connection with another Bluetooth device, it will automatically switch to the transparent transmission state. In this state, AT commands will be disabled, and every byte received by the module from the host MCU will be transmitted intact to the remote Bluetooth device.

How to send and receive Bluetooth data in AT command mode?

In AT command mode, different modules may adopt different methods to send and receive Bluetooth data. For detailed information, please refer to the relevant command manual of the module.

How to switch between transparent transmission and AT command modes?

Many Feasycom Bluetooth data transmission modules (e.g., BT826, BT836B, BT909, BT616, etc.) support both transparent transmission and AT command modes.

a. When the module is not connected to any Bluetooth device: 1. Send AT+TPMODE=0 to enable AT command mode 2. Send AT+TPMODE=1 to enable transparent transmission mode b. When the module is connected to a remote Bluetooth device (this function needs to be enabled with the AT+PIOCFG=1,0 command): 1. Set the specified pin (such as Pin9 of BT826, BT836B, BT909, etc.) to high level to enable AT command mode 2. Set the specified pin (such as Pin9 of BT826, BT836B, BT909, etc.) to low level to enable transparent transmission mode

Does the module support iBeacon and Eddystone?

Yes, but customization may be required. Please contact Feasycom for details.

Why can’t I connect to the module through the built-in settings app on my phone?

Bluetooth peripheral devices can be connected via the built-in settings app of the phone, such as Bluetooth speakers, Bluetooth headsets, Bluetooth keyboards, Bluetooth mice, etc. When a Bluetooth peripheral device cannot be connected via the settings app (for example, the Bluetooth module only supports SPP/GATT protocols), a specific mobile app such as Feasyblue is generally required to connect to such modules.

Can connection be established without pairing?

Yes. For SPP/BLE connections, the module can be configured to bypass the pairing process to achieve fast connection. When other services such as Bluetooth audio and HID are enabled, only the simple pairing method can be used to simplify the pairing process, and it cannot be bypassed.

How to receive messages and emails via Bluetooth?

If the target phone is an iOS device, the module can obtain them directly.

If the target phone is an Android device, an app is required to realize this function.

Why can’t I connect to the BLE module?

Some applications only support connecting to BLE modules with specific UUID groups. Different suppliers may use different UUIDs, and only when the application and the BLE module support the same group of UUIDs can they connect to each other. For most Feasycom modules, the default BLE UUIDs are:

Service UUID: FFF0

Notify UUID: FFF1

Write or Write without Response UUID: FFF2

Can BLE UUIDs be modified or customized?

Yes, but it may be necessary to replace the module’s firmware. For details, please contact Feasycom.

How to change the device icon displayed for a Bluetooth device on a phone or PC?

You can use AT+COD to set the device type (COD) of the module, and then the displayed icon will change. For example, use

AT+COD=001F00 to set it to the Bluetooth icon. The commonly used COD table is as follows.

COD	Icon
001F00	Bluetooth
40680	Printer
240404	Headset

For more configuration references: [COD]

Why doesn’t the Bluetooth device name update after I change it?

The new device name will take effect after restarting the module.

If using an iOS device, it is recommended to use the device name in advertisementData when updating the name on the app, instead of using the original API for name update.

What does “supporting Bluetooth master-slave synchronization” mean? What does “supporting both Bluetooth master and slave modes” mean?

It means that the module can not only act as a master device to search for and connect to nearby slave devices, but also act as a slave device to be scanned and connected by master devices.

How many connections can Bluetooth support?

Some Feasycom modules can support up to 17 Bluetooth connections, i.e., 7 classic Bluetooth connections and 10 Bluetooth BLE connections.

Is this module a standalone module?

RF modules are not standalone modules, while SoC modules are standalone modules. The definitions of RF modules and SoC modules are as follows.

RF module and SoC module

Category	Description	Remarks
RF Module	RF modules do not have an on-board MCU to run the Bluetooth protocol stack and must have an external host MCU	FSC-BT825B, FSC-BT805B, FSC-BW101, FSC-BW121, etc. are RF modules
SoC Module	SoC modules have an on-board MCU to run the Bluetooth protocol stack and do not require an external host MCU	In Feasycom products, all BLE modules, most Bluetooth dual-mode modules and audio modules are SoC modules

Can Bluetooth modules be debugged wirelessly?

Most of Feasycom’s Bluetooth modules support over-the-air debugging. The operation steps are as follows:

1. Install Feasycom’s Android (recommended) or iOS app FeasyBlue

2. Open the app, enter the settings page, and click Parameter Modification

3. Enter the password 20138888, then you can configure the module as needed

4. Bluetooth name, PIN code, and baud rate support quick settings; other settings require entering relevant AT commands. Fill in parameters or commands in the input box, then check the box on the right and click Start

5. Select the device to be configured and wait for completion

How to improve data transmission speed and stability?

1. Increase the serial port baud rate and enable serial port hardware flow control (RTS, CTS).

2. When high data reliability is required, it is recommended that the sending and receiving ends enable handshake and verification mechanisms.

3. The data packet sent by the host computer to the module each time should not exceed the module buffer size. Depending on different models, it is usually 1/2/4Kbytes. You can confirm the specific buffer value with Feasycom technical support.

How to send AT commands in transparent transmission mode?

1. When the module is in transparent transmission mode, you can switch to command mode by pulling up the specified I/O port. After the command is sent, you can pull down this IO to switch back to transparent transmission mode.

2. The module is in command mode by default when not connected, and in transparent transmission mode by default after successful connection.

How to connect two modules via SPP

Some modules (such as BT836, BT909, etc.) support both SPP master and slave modes. The following operations can be used to connect two modules via SPP: 1) Send the AT+SCAN=1 command to search for nearby Bluetooth devices; 2) Send AT+SPPCONN=<MAC address> to connect to the SPP slave module.

Bluetooth Low Energy Module

[BT630] How to test high-speed BLE transmission (65kB/s)?

1. Use an iPhone 8 or newer model with iOS 13 or later

2. Send AT+BAUD=921600 to the module to set the baud rate to 921600.

3. Install the FeasyBlue app and use it to establish a connection with the Bluetooth module.

4. After the connection is established, set the sending interval of the FeasyBlue app to 0ms

5. Select to send a file, choose 2MB, and wait for completion.

[BT630] Does this module support transparent transmission mode?

Transparent transmission version firmware supports it (e.g., V2.0.8),

multi-connection firmware (e.g., V5.1.7) only supports sending/receiving data via AT commands and data indication.

[BT630] How to test the multi-connection function of BT630?

The BT630 module has multi-connection firmware (e.g., V5.1.7). The following steps demonstrate how to test its multi-connection function:

1. Send AT+SCAN=1 to scan nearby BLE devices.

2. Send AT+LECCONN to connect to a specific BLE device.

3. Repeat steps 1-2 to establish multiple connections

4. Use AT+LESEND to send data to a specific BLE peripheral

[BT630] Can the transmit power be modified? How to modify it?

Firmware version 5.0.6 (or later) supports modifying the transmit power. The adjustable power table is:

Tx power (dBm) 0 4 8 -12 -16 -20 -40

For example: Send AT+TXPOWER=0 to set the transmit power to 0dBm.

Which Bluetooth modules support Bluetooth 4.0 low energy function?

1. The three modules FSC-BT616, FSC-BT625, and FSC-BT626 support Bluetooth 4.0 low energy function, and their standby power consumption can be within 50 microamps;

2. The two modules FSC-BT816S and FSC-BT803 support classic Bluetooth low energy mode, and their standby power consumption can be within 1mA.

Bluetooth Dual-mode Module

Why does the module have two device names?

When you search with an Android phone, you may sometimes find that the module has two names, which indicates that you are using a Bluetooth dual-mode module, one is the classic Bluetooth name, and the other is the BLE Bluetooth name.

[BT826B] How to enable low power mode?

1. Send AT+LPM=1 to enable low power mode

2. Restart the module, and the module will automatically enter low power mode

[BT826E] Does it support low power mode?

Currently, BT826E does not support low power consumption. If you need a module that supports low power mode, FSC-BT826B is recommended, and the power consumption in its low power mode is as follows:

Not connected: 2.2 mA

BR/EDR connected: 1.5 mA

BLE connected: 2 mA

[BT836] How to send HID data?

Method of sending HID data under default configuration (HID transparent transmission):

1. Use an HID host (such as a smartphone) to connect to the BT836 module

2. Send HID codes (ASCII characters) directly from the MCU to BT836 via UART.

If you want to send with key values:

1. Send AT+HIDMODE=0 to enable HID key value mode

2. Send AT+TPMODE=0 to enable AT command mode

3. Use an HID host (such as a smartphone) to connect to the module

4. Use AT+HIDSEND to send HID data. Each group of data consists of a modifier and a key value, so the data length is always a multiple of 2, and the HID data payload should be in binary format.

The bitmap of modifiers is as follows:

Bit	Key
0	LEFT CTRL
1	LEFT SHIFT
2	LEFT ALT
3	LEFT GUI
4	RIGHT CTRL
5	RIGHT SHIFT
6	RIGHT ALT
7	RIGHT GUI

[BT836B] How to wake up the module when low power mode is enabled?

When the module enters low power mode, the LED pin (Pin32) will turn to low level. This does not mean that the module has lost the connection with the remote Bluetooth.

When the module enters low power mode, the first data packet sent to the module via UART is only used to wake up the Bluetooth and will be discarded. Therefore, before normal communication, a dummy data packet needs to be sent first.

Sending timing: Send a fake packet, wait for 100ms, then communicate normally.

The first data packet from the remote Bluetooth device can also wake up the module, and the first data packet will be correctly sent to the MCU without being discarded.

[BT836B] How to switch to high-speed transmission mode?

For modules that support multi-connection, you can send AT+HSM=Param to the module to switch back and forth between multi-connection mode and high-speed transmission mode.

1. Send AT+HSM=1 to switch to high-speed transmission mode

2. Send AT+HSM=0 to switch to multi-connection mode

[BT836B] How to test high-speed SPP transmission (85kB/s)?

The SPP data rate varies by phone. 85kB/s is the maximum speed tested on several specific phones. The method to test the maximum SPP data rate with your phone is as follows:

1. Send AT+BAUD=921600 to the module.

2. Install the FeasyBlue application and use it to establish a connection with the Bluetooth module.

3. After the connection is established, set the sending interval of the FeasyBlue app to 0ms

4. Select to send a file, choose 2MB, and wait for completion.

Bluetooth Audio Module

[BT80X] What codecs are supported and how to configure them for A2DP source applications?

The BT80X series includes FSC-BT802, FSC-BT803, FSC-BT806A and FSC-BT806B

The codecs supported by FSC-BT802, FSC-BT803, FSC-BT806A include SBC, aptX, aptX LL. AAC codec is not supported.

The codecs supported by FSC-BT806B include SBC and aptX. AAC and aptX LL codecs are not supported.

1. If the remote Bluetooth device also supports aptX, the aptX codec will be automatically selected; otherwise, the SBC codec will be applied.

2. If the module supports the aptX LL codec and the peer Bluetooth device has aptX LL enabled, send AT+APTXCFG=1 to start aptX LL, so that aptX LL can be used to debug audio.

[BT80X] Why is aptX not displayed on the phone?

If the module is connected to two devices at the same time, aptX is not available. aptX only works in one-to-one scenarios.

[BT80X] Can disconnection and connection ringtones be added?

Yes, Feasycom can set the module with the ringtone files provided by the customer.

[BT909] How to establish an A2DP source connection?

1. Send AT+PROFILE=83 to switch to transmitter mode.

2. Send AT+SCAN=1 to scan for nearby Bluetooth devices.

3. Send AT+A2DPCONN=MAC to connect to the target BT device.

4. Send AT+A2DPAUDIO=1 to activate A2DP.

5. When +A2DPSTAT=3 is received, it indicates that the A2DP connection is established.

[BT909] How to create an HFP source connection?

1. Send AT+PROFILE=83 to switch to transmitter mode.

2. Send AT+SCAN=1 to scan for nearby Bluetooth devices.

3. Send AT+HFPCONN=MAC to connect to the target BT device.

4. Send AT+HFPAUDIO=1 to activate HFP audio routing.

5. When +HFPSTAT=3 is received, it indicates that the HFP connection is established.

[BT909] Does the module support noise reduction processing?

No, but some other Feasycom modules support noise reduction processing, such as BT802, BT806B, etc.

[BT100X] What is the difference between BT1006A and BT1006C?

BT1006A does not support aptX. BT1006C supports aptX, and the license is also included.

[BT100X] Can wireless Bluetooth headsets use aptX?

No, aptX, aptX LL and aptX HD cannot be used in Bluetooth headsets.

[BT100X] Does the module support iPhone Siri?

Yes, it can support Siri.

[BT1006C] Can AGC be debugged?

Tools for debugging AGC can be provided.

Hardware Related

General

How to build a minimum Bluetooth data transmission system?

A minimum system requires four pins: VDD_3V3, GND, UART_TXD, UART_RXD. For pin assignment, please refer to the module specification.

Are there development boards for the modules?

Yes, you can visit [Development Board Overview] to learn about development board product information

What is the minimum input current of the Bluetooth module?

Different Bluetooth modules have different peak currents, usually between 40 and 70 mA, so 100 ~ 150 mA is the recommended minimum input current. If the module’s current supply is insufficient, it will affect the operation of the module.

What is the logic level of the module’s UART?

The module’s UART uses 3.3V TTL logic level by default and can be connected to the UART of a 3.3V MCU. If other logic levels are required, please contact Feasycom FAE for more information.

Can the I/O pins of the module support 5V voltage?

No, a level conversion circuit must be used.

How to use a module without an onboard antenna?

In the verification and testing phase, the simplest method is to solder a 30mm wire to the antenna output pin, which can be used as a temporary antenna.

What principles should be followed when designing a high-performance PCB antenna?

1. It is recommended to design the antenna as a component package according to its size, which facilitates placement and subsequent project design, and can avoid size changes caused by repeated dragging and modification.

2. The antenna is connected to the ground wire. No components or wiring should be placed around the effective part of the antenna and its lower layer (i.e., the back), and no copper foil should be laid, otherwise, it will affect the transmission and reception of signals, and may even fail to work normally.

3. The antenna ground point needs a large area of grounding and more vias.

4. The antenna should be designed at the edge of the PCB, facing the front panel as much as possible, and it is required to avoid ferrous structural parts around it.

5. The distance between the antenna and surrounding components should be at least 5mm. For specific descriptions, please refer to the specification of the corresponding module model, which contains detailed placement diagrams.

Can the SPI/I2C interface of the module be used for data transmission?

Yes, but customization may be required. Please contact Feasycom for more information.

How to avoid audio noise floor in Bluetooth audio modules?

1. The ground wire should be as thick as possible, and the ground plane should be complete without segmentation. For example, the upper and lower layers of ground copper wires are connected only through a few vias, which seems to be a path, but in fact, the ground plane has been segmented.

2. The ground wires are divided into digital ground and analog ground, and they should follow their own lines without mixing.

3. Module 3.3V power supply: independent power supply, connected to the module power pin after the filter capacitor.

4. Audio wiring needs to be grounded and should not cross or be parallel to data communication lines (if crossing is necessary, cross at a 90-degree angle).

Do Bluetooth audio modules support I2S/PCM output?

Yes, I2S/PCM for audio transmission can be enabled and configured via AT commands.

Does the module support MCLK for I2S output?

No, the module supports 4-wire I2S (BLCK/WS/SDIN/SDOUT). It is recommended to use a codec that does not require MCLK.

[BT802] How to charge a lithium-ion battery?

Please refer to the application schematic in the data sheet. The maximum charging current is 200mA. If a higher charging current is required, please use an independent charging chip.

The charging circuit is very simple. If the VBAT_IN pin is connected to the positive pole of the battery and the VCC_CHG pin is connected to the positive pole of the 5V power supply, charging will start when the battery voltage drops to a certain level.

The charging circuit is not implemented on the FSC-DB103 development board, but you should be able to implement it easily.

Other

General

What is Bluetooth 4.0?

Bluetooth 4.0 consists of Bluetooth BR/EDR (also known as classic Bluetooth) and Low Energy (LE, first introduced in Bluetooth 4.0). Bluetooth 4.0 is backward compatible with Bluetooth 3.0/2.1/2.0. It defines many profiles for data and audio communication, such as SPP/GATT/HID for data communication, and HFP/A2DP/AVRCP for audio communication.

What is Bluetooth dual-mode?

Bluetooth dual-mode supports both classic Bluetooth and BLE simultaneously.

What are the advantages of Bluetooth dual-mode modules?

There are two main smartphone platforms: iOS and Android.

iOS devices can communicate with Bluetooth peripherals via GATT or SPP (requires MFi certification). Since MFi coprocessors are expensive and MFi certification is not easy to obtain, most customers prefer to use GATT for communication with iOS devices.

The Android system has supported BLE since Android v4.3, but due to severe system fragmentation, many Android phones on the market support BLE with poor compatibility. Therefore, it is recommended to use the traditional Bluetooth SPP profile for data communication.

To sum up: When a product needs to support both iOS and Android devices, Bluetooth dual-mode products are the mainstream choice in the market currently.

What is Bluetooth BLE?

Devices that only support the Low Energy part of Bluetooth 4.0 are called Bluetooth BLE devices.

What is MFi certification, and when is MFi certification required?

Apple MFi (Made for iPhone/iPod/iPad) certification is a license for authorized manufacturers to produce accessories for iOS devices. Each accessory requires an MFi coprocessor chip.

When you find that the data rate of BLE GATT cannot meet your needs, you may need to obtain MFi certification to use the SPP protocol on iOS devices.

What is the typical transmission range of Bluetooth modules?

Most Bluetooth devices are Class 2 with a range of 10 meters, but some Bluetooth modules are Class 1 with a range of 100 meters or more. For example,

Feasycom’s FSC-BT909 can reach a range of 300 meters.

What are the maximum data rates of SPP and GATT?

Different modules may have different maximum data rates. Taking BT836B as an example, when the module operates in high-speed mode under optimal conditions (distance between Bluetooth devices is less than 1m, no obstacles between Bluetooth devices, and the remote Bluetooth device has excellent performance) with a UART baud rate of 921600 bps, its maximum SPP transmission speed can reach 82 kB/s, and its maximum reliable BLE transmission speed can reach 62 kB/s.

Can the module support iBeacon, WeChat connection, and WeChat Shake function?

Yes, it requires specific program support. For details, please consult Feasycom engineers or refer to relevant technical documents.

Why do Chinese characters sent from the mobile phone display as garbled characters on the serial port?

Please confirm whether the currently used serial port tool supports Chinese character sets. If it does, please confirm that the received Chinese characters correspond to it (such as UCS2, UTF8, etc.).

Or contact Feasycom engineers to obtain a serial port tool that supports Chinese characters.

Appendix

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