pico w Bluetooth USB adapter

just trying to get my head around it!

The problem is that Bluetooth, like networking, is a general purpose service. It supports keyboards, nice, serial ports, headphones, speakers, zipping files between devices, and other stuff.

Therefore, it is, like networking, based upon a stack architecture.

Which means that one doesn’t just write a little program or module to “do Bluetooth”. There’s the hardware driver, there’s the device enumeration, there’s various types of authentication, there’s drivers for each sort of device (which may include all manner of protocol negotiation – there are different ways to send data to headphones for example (aptX, aptX HD, SBC…) and note that audio devices take audio data (probably PCM) and translate it on the fly to whatever format the device wants, plus sending in such a way that it can run in real-time for hours without stuttering).
Oh, and there’s also a back channel these days for sending up the stream information on what’s currently playing. Though, only a few things actually support this.
Oh, and more advanced things may support multiple concurrent audio devices along with trickery like “only play the left audio channel to this one”.

That’s just music. One of the many possibilities of Bluetooth hardware.

So, yeah, “it’s complicated”.

Also seems to work through USB with Bookworm64 on Pi4 and Samsung Galaxy phone.
Just a thought, could it be modified to use some of the I/O on the Pico to add hardwired keys for those that are useful on RISC OS, but are sadly lacking on compact keyboards?

It’s possible – it’s also possible to do it in the usb keyboard driver – I’ll add it to the list of things to look at.

Anyone like to try this uf2 file for the raspberry pi pico bt_usb_kbd-0_02.

This version should work with bluetooth LE and classic keyboards and mice.

I can connect both my bluetooth classic keyboard and bluetooth LE mouse to it simultaneously. Instructions are in the README file. works plugged into Pi4 and Armx6

2) plug the pico w into a riscos machine with the button on the pico held down.
3) A Fat32 disc drive appears for the pico open it and drop bt_usb_kbd/uf2 into the filer window just like you are saving a file.

This sounds ingenious. Do I understand correctly that the Pico W with the button held down behaves like a USB mass storage device, which RISC OS (and any other OS) can access? And that it programs itself with whatever you dump onto the device?

What a very neat interface, and nice to be able to do it from RISC OS!

Yes, that’s the way it works. I’ve got a Pico based LED clock, and have improved the Chinese C software on it (a 3rd level of dimming so we can sleep at night, and made the 4 & 7 digits look less horrible), but it was a pain having to take it apart in order to press the button to load new software. I solved this by careful measuring and drilling a hole directly over the reset button, so I can reprogram it without taking a dozen screws out of it. The clocks going back has reminded me I still haven’t got around to putting in automatic adjustment for daylight savings time.

If you have the default serial usb interface on the pico you can put the pico into programming mode by setting the baud rate to 1200 – The XHCI driver doesn’t like it but it works. There’s also a usb reset interface but I’ve not tried that.

The bluetooth software I wrote doesn’t do this as I had to add my own serial interface.