We tested the HFP distance of BT909 module. Here is the report:
Sunny; No obstacles around; Straight road; Product is 1.5m above the ground.
1. Prepare two BT909 modules, firmware version: VER=FSC-BT909, V3.2.6, 20181105.
2. Solder the two BT909s to the daughter board and prepare two sets of FSC-TL001 development boards with Codec.
3. Install two BT909s on the FSC-TL001 development board and power them separately with two computers.
4. Send AT command to change the mode of two BT909 modules:
Master mode command: AT+PROFILE=19
Slave mode command: AT+PROFILE=1707
1. Use the serial port tool to query the MAC address code of the slave module.
2. Master module connect to the slave module via the serial port tool.
XXXXXXXXXXXX represents the twelve-bit slave MAC address.
AT command of connecting to the slave module: AT+HFPCONN=XXXXXXXXXXXX
3. After successful connection, master module send audio command to slave module via serial port tool.
1. Plug the headphone or speaker into the SPK2 interface of the two development boards FSC-TL001.
2. Sound can be heard from headphone or speaker of the master FSC-TL001 development board when speaking at MIC of slave FSC-TL001 development board.
3. Sound can be heard from headphone or speaker of the slave FSC-TL001 development board when speaking at MIC of master FSC-TL001 development board.
4. Fix one of the two devices, move another, keep talking, ensure the sound quality is clear, no noise, the farthest distance without transposition
The longest distance is 90m, if out of the range, the sound will be noise, trembling, intermittent and other issues.