TTL Bluetooth adaptor

Yes, I use those extensively. Extremely useful for outdoor mounted devices for example: https://openwrt.org/toh/zyxel/nr7101#serial

I have been using "jdy-31" modules without any carrier board. They are running a slave only firmware which makes the configuration impler. And dropping the unnecessary carrier board avoids the regulator voltage drop. So far I have been using these as BR devices, but the last batch I got had a firmware with BLE support as well. Which I guess can be useful in some settings.

Personally I simply use rfcomm on a console server with a bluetooth dongle to manage these. The simplest one I got is a Unifi UAP AC Pro running OpenWrt with conserver :slight_smile:

The Bluetooth modules are configured by AT commands on their UART port. This management interface is active as long as there is no active Bluetooth connection. Definitely easiest to preconfigure before installation using a USB TTL adapter. But it is possible to configured them after mounting too, as long as you can access the attached device through some other channel to send commands out on the console port. Mostly useful for simple reconfiguration of device name etc.

The only issue I've had so far after installing these all over the place was a Netgear GS108Tv3 switch where the 3.3V terminal wasn't connected. Other than that, I've had great success with assorted routers, switches and APs.

I bought a new batch from this seller just a couple of months ago: https://www.ebay.com/itm/385916963172
Can definitely recommend both modules and seller.

EDIT: Example permanent (soldered!) connection to my brand new U6+. This has been nicely hidden inside the case on the now wall mounted AP, without anything visible on the outside:

EDIT2:

I've never tried this, but the jdy-31 or similar without any additional regulator might work on 1.8V. Provided that you have a 1.8V supply. The spec I got is a little sketchy, but it claims

Operating voltage: 1.8-3.6V (3.3V recommended)

I assume the IO voltages will be slightly below Vcc . You should probably veryfy this with a multimeter before frying anything.

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