The KRC-86B V4.0 is a CSR8630-based Bluetooth module that is useful as an A2DP-only audio receiver (no headset or hands-free profile, paired phones will not send voice calls to the module) and available from eBay/AliExpress for ~$6.50USD/shipped – this page describes how to access and configure the CSR8630 to change a few common settings (Bluetooth name, codecs, audio tones, etc).

As shipped, the module has the following configuration:

• Bluetooth discoverable name: KRC-86B V4.0
• Codecs: SBC
• Audio tones: tone at minimum volume, tone at maximum volume
• Discoverable: automatically discoverable while Bluetooth is disconnected
• Multipoint: disabled
• Analog line-in: automatic switching between line-in and Bluetooth

These and other options (other than the line-in switching) can be configured on the CSR8630 over SPI using an FTDI FT232R-based USB-serial module (~$2USD/shipped – likely counterfeit FT232R chips but work fine), CSR BlueSuite software (register for a free account, Windows-only but works in a virtual machine), and the csr-spi-ftdi driver. Fortunately, the necessary CSR8630 SPI pins are exposed as pads on the module for easy access (labeled NC):

• INL: analog line-in, left channel
• INR: analog line-in, right channel
• AGND: analog ground
• NC: SPI MISO
• OUTL: analog line-out, left channel
• OUTR: analog line-out, right channel
• AGND: analog ground
• NC: SPI SS
• NC: SPI SCLK
• NC: SPI MOSI
• LED-
• LED+
• NC: SPI/PCM mode selection
• GND
• VCC: +5vdc

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