Bluetooth

Some wireless variants of the ConnectCore 6 system-on-module assemble Atheros chip AR6233, which is Bluetooth capable. These modules are built with coexistence in mind and handle the Bluetooth coexistence internally.

The Bluetooth interface is connected to the i.MX6 via the UART2 port and GPIOs for some AR6233-specific pins.

Features

Atheros chip AR6233 supports the following Bluetooth features:

• Classic Bluetooth:
  • GAP: Generic Access Profile; discovery and pairing
  • HDP: Health Device Profile
  • SPP: Serial Port Profile
  • PAN: Personal Area Networking
  • HSP: Headset
  • HFP: Hands-Free Profile, specifically for cars
  • FTP (OBEX): File Transfer Profile
  • OPP (OBEX): Object Push Profile
  • HID: Human Interface Device (mouse, keyboard, joystick)
  • A2DP: Advanced Audio Distribution Profile
  • AVRCP: Audio/Video Remote Control Profile
  • Bluetooth Low Energy (BLE)
  • GAP: Generic Access Profile
• The following profiles have been validated in Digi Embedded Yocto:
  • Classic Bluetooth:
  • GAP: Generic Access Profile; discovery and pairing
  • HDP: Health Device Profile
  • Bluetooth Low Energy (BLE)
  • GAP: Generic Access Profile

The following profiles have been validated in Digi Embedded Yocto:

• Classic Bluetooth:
  • GAP: Generic Access Profile; discovery and pairing
  • HDP: Health Device Profile
• Bluetooth Low Energy (BLE)
  • GAP: Generic Access Profile

Kernel configuration

You can manage the Bluetooth driver support through the kernel configuration option:

• Atheros AR300x serial support (CONFIG_BT_HCIUART_ATH3K)

This option is enabled as built-in on the default ConnectCore 6 SBC kernel configuration file.

Platform driver mapping

The Atheros AR300x Bluetooth driver is located at drivers/bluetooth/hci_ath.c.

Device tree bindings and customization

Although there are no generic device tree bindings for the Bluetooth driver itself, there is a bluetooth node on the ConnectCore 6 device tree file that contains the following properties:

• digi,pwrdown-gpios: a GPIO connected to the PWD_L pin of the AR6233 chip. When driven low, it turns off all the core voltages of the Bluetooth block and all state information is lost.
• digi,disable-gpios: a GPIO connected to the BT_DISABLE pin of the AR6233 chip. When active, it disables the Bluetooth block (the radio and the UART interface) and places it into sleep state.

This node is also used as a placeholder for containing Digi's MAC address for the Bluetooth chip.

ConnectCore 6 SoC variant specific device tree

bluetooth {
        digi,pwrdown-gpios = <&gpio_extender 4 0>;
        digi,disable-gpios = <&gpio1 9 GPIO_ACTIVE_HIGH>;
        /* U-Boot will fill in the MAC address here */
};

MAC address

The MAC address of the ConnectCore 6 Bluetooth interface is stored in the ConnectCore 6 eMMC as part of the U-Boot bootloader environment (variable btaddr).

Before launching the operating system, U-Boot writes the MAC address into the device tree bluetooth node as property local-mac-address.

Known issues and limitations

• Using Bluetooth in parallel with wireless (coexistence mode) can affect your Bluetooth performance.
• The driver only supports up to 10 simultaneous BLE connections.