BLE/GATT bindings for Bluedroid

[ivmarkov]

There is already esp32-nimble which is a binding for the NimBLE stack in ESP IDF (a bit lighter-weight but BLE only), yet I thought it would be good to complete the existing Bluedroid bindings in esp-idf-svc (which are currently only exposing Classic BT) with the BLE/GAP/GATT functionality.

W.r.t. GATT, currently only GATT Server (peripheral) functionality is exposed, but adding support for GATT client (central) would not be hard at all.

Still needs to be tested (and documented a bit) hence in Draft status.

EDIT: Don't pay attention to the changes in Cargo.toml, sdkconfig.defaults and config.toml. These will be reverted later.

[Vollbrecht]

Cool that you are working on this. Did you try the api only on a esp32? Can i use it on a non esp32 by only enabling the BLE stuff in the sdkconfig? Can you add a quick and dirty example that spawn a BLE gatt server, i can test it out later if it works on my esp's

[ivmarkov]

Cool that you are working on this. Did you try the api only on a esp32? Can i use it on a non esp32 by only enabling the BLE stuff in the sdkconfig?
Yes, that should be possible.

Can you add a quick and dirty example that spawn a BLE gatt server, i can test it out later if it works on my esp's

Yes I'm working on that but it will take some time (hence why the PR is in a draft status).

Once the PR is in a final state, I'll ping you. For now, what is reviewable is the overall approach (which is not much different, if at all, from the Classic BT Bluedroid code path).

Also, FYI some renames would be coming. The names of the GATT server events are suboptimal. I copied them from somewhere but they suck. More human readable names coming, as well as more APIs.

[ivmarkov]

Cool that you are working on this. Did you try the api only on a esp32? Can i use it on a non esp32 by only enabling the BLE stuff in the sdkconfig?

Yes, the BLE part should work fine on other chips.

[Vollbrecht]

Do you plan on including a example in the examples dir with this PR or as a follow up?

[ivmarkov]

Do you plan on including a example in the examples dir with this PR or as a follow up?

I'll do as this PR. I just can't get there yet.

[Vollbrecht]

Do you plan on including a example in the examples dir with this PR or as a follow up?

I'll do as this PR. I just can't get there yet.

No pressure !

[Vollbrecht]

Thanks for pushing the example! i will try it out later. One thing we might want to directly provide in the example header is the specific set of sdkconfig settings so a user can copy paste them when trying to recreate it in a template.

[ivmarkov]

@Vollbrecht Will look into the CI failure tomorrow. The settings are copied verbatim from another project where they work, but here they fail. Only difference is that the other project uses wifi, which might link against the coex driver. While the BT example doesn't.

[ivmarkov]

In any case, the settings should work for anything except the esp32, i.e. you can test on the c3 and/or other riscv whenever you want.

[ivmarkov]

@Vollbrecht Will look into the CI failure tomorrow. The settings are copied verbatim from another project where they work, but here they fail. Only difference is that the other project uses wifi, which might link against the coex driver. While the BT example doesn't.

No I was wrong! The linking behavior is NEW for ESP IDF v5.2.0. With 5.1.X it works just fine!
I'll now check if we have the same error with version > 5.2.0. If not, I guess we can just skip this version. If yes, we need to figure out what is going on...

[Vollbrecht]

The link issue here is a bit different as to our general linking issue with idf 5.2 and no_std its not missing something out of the compiler provided library's but something from within esp-idf. Still out of curiosity, checking how it would pen out when you run it with "-C default-linker-libraries"

[ivmarkov]

The chance "-C default-linker-libraries" to fix it is likely 0. We are missing a symbol from the Wifi/BT coexist driver. "-C default-linker-libraries" kinda helps with symbols from libc & intrinsics, but that's pretty much all.

[Vollbrecht]

We are missing a symbol from the Wifi/BT coexist driver

interesting that it did work on riscv v5.2, Our other linker issues were always present on all platforms

[ivmarkov]

esp32 is the only chip which has classic BT.

[Vollbrecht]

ah i missed that btdm_rf_bb_reg_init is a BT classic thing, the rfcoxist.a should be present on all esp variants in some form thats why i had the wrong picture here.

[ivmarkov]

Short update on the (now fixed) build failure:

• Error was in the wifi example, not in bt_gatt_server which is introduced with this patch
• Error only with ESP IDF 5.2.0 (ESP IDF 5.2.1+ have this fixed) and esp32 MCU
• Error is this: d01571b , first found by @MartinBroers (thanks again Martin!). Workaround: either don't enable BT, or if enabling BT, also enable BT Classic

I've tested the example on both esp32 and esp32c3, so IMO this stuff is ready for merging now.