Pharma site, so I’m stuck with what’s validated: a Pi 3B running a Raspbian Stretch image our validation group signed off years ago. Upgrading the OS means re-validation, which means months.
New requirement: read eight BLE temperature tags in a cold room and forward them to Hermetry. Same Pi already reads a chiller over Modbus RTU on the serial header. Bluetooth simply isn’t there:
$ bluetoothctl
No default controller available
$ hciconfig
$ dmesg | grep -i blue
[ 6.112] Bluetooth: Core ver 2.22
[ 6.118] Bluetooth: HCI device and connection manager initializedNo hci0 at all. Am I missing a package or is this a hardware fault?
Have you tried a full power off, not just reboot? Fixed my Pi once.
Is pi-bluetooth installed? Some minimal images leave it out.
Power cycled, yes. pi-bluetooth is installed. systemctl status hciuart says failed, „Failed to start Configure Bluetooth Modems connected by UART“.
hciuart failing on a Pi 3 that also does Modbus on the serial header: I’d bet whoever set up the Modbus put dtoverlay=pi3-disable-bt in /boot/config.txt to get the good UART on GPIO14/15. That overlay switches the BT chip off completely, so hciuart has nothing to talk to.
You can have both. On Stretch use the other overlay, which gives BT the mini UART and keeps the PL011 on the header:
# /boot/config.txt
#dtoverlay=pi3-disable-bt
dtoverlay=pi3-miniuart-bt
core_freq=250core_freq=250 keeps the mini UART’s clock stable, BT gets flaky without it. Also make sure console=serial0,115200 is not in cmdline.txt. Reboot, then sudo systemctl restart hciuart and hciconfig should show hci0.
Your Modbus side keeps /dev/ttyAMA0, so the chiller code shouldn’t notice.
Exactly that, pi3-disable-bt was there with a comment „for chiller“ from 2019. Swapped to pi3-miniuart-bt + core_freq=250, hci0 is up, all eight tags show in a scan and the chiller polling didn’t miss a beat. Config change only, so validation treats it as a minor change.
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