🛠 Réveiller le Bluetooth de l'AP6212 : hci_uart et firmware BCM

Objectives

On the BPI-M2 Zero, the Bluetooth of the AP6212 combo is not a USB controller: it is a serial HCI interface on UART1 (node brcm,bcm43438-bt in the device tree, 1,500,000 baud, RTS/CTS on PG11-PG13). Depending on the kernel version, loading the firmware and attaching the hci_uart discipline do not happen automatically — user feedback documents a "no BT controller found" error requiring manual loading of hci_uart and attaching the serial port by hand. You will bring the controller up to bluetoothctl and perform a BLE scan.

Hardware

• BPI-M2 Zero running Armbian (kernel 6.x) with console access
• BCM43xxx firmware package present (linux-firmware non-free/brcm depending on the image)
• A smartphone or BLE sensor to detect
• U.FL antenna screwed in (BT shares the module's antenna)

Complete code

sudo apt update && sudo apt install -y bluez

# 1) Le noyau a-t-il déjà créé le contrôleur ?
bluetoothctl list
dmesg | grep -i -e bluetooth -e hci -e 4343

# 2) Sinon, apport manuel : firmware + discipline hci_uart + attach UART1
sudo apt install -y psmisc
sudo rfkill unblock bluetooth 2>/dev/null
sudo modprobe hci_uart
# Attacher le port série de l'UART1 au discipline HCI (BCM)
sudo sh -c 'echo "bcm43xxx 0" > /sys/bus/serial/device_add' 2>/dev/null || \
sudo btattach -n -B -s 1500000 /dev/ttyS1
sleep 3
hciconfig -a          # hci0 doit être apparu

# 3) Scanner
bluetoothctl
#   power on
#   agent on
#   scan on        # les périphériques BLE défilent
#   quit

# 4) Rendre le réveil permanent si nécessaire
echo hci_uart | sudo tee /etc/modules-load.d/bt.conf

Expected verification

After attachment, hciconfig -a displays hci0 with a MAC address; bluetoothctl scan on scrolls through devices (watches, phones, sensors) within a few meters; the link remains stable after power on/off. Wi-Fi and BT coexist on the same antenna.

Common errors

• Targeting ttyS0: this is the console (UART0); the AP6212's BT is on UART1 (ttyS1, pinout PG11-PG13).
• Running btattach at 9600 or 115200: the module expects 1,500,000 baud, otherwise the first firmware exchange times out.
• Forgetting the RTS/CTS lines: without hardware flow control at 1.5 Mbaud, firmware loading fails due to overflow.
• Missing brcm/ firmware in the minimal image: hci_uart loads but the controller never responds — install the appropriate firmware package.
• Blaming the hardware when a kernel regression is the cause: the Armbian forum documents versions where the BT of this family no longer initializes automatically — hence the manual procedure.