Maybe Bluetooth device implementation flaws cause failures in pairing(org.bluez.Error.AuthenticationCanceled)?

[hyx0329]

Recently I'm playing around with an SBC with RTL8723DS(wifi+bt combo chip) and found it cannot pair with my ZMK keyboard. Initially I thought it's a bug in linux/bluez or ZMK, however tests showed that maybe the chip is the one to blame.

I tried to pair with the keyboard using bluetoothctl(with bluez 5.76, 5.74, 5.68), but got:

[bluetooth]# pair F5:E6:96:XX:XX:XX
Attempting to pair with F5:E6:96:XX:XX:XX
[CHG] Device F5:E6:96:XX:XX:XX Connected: yes
[CHG] Device F5:E6:96:XX:XX:XX Connected: no
[bluetooth]# Failed to pair: org.bluez.Error.AuthenticationCanceled

However on Intel AC8265(BT4.2) and RTL8761B(BT5.0), everything works fine.

Here's a picture of btmon log comparison:

The datasheets for realtek chips(collected from internet):

• RTL8723DS.pdf
• RTL8761B.pdf

ZMK's doc states that it can only connect to BT4.2 or newer devices due to the link encryption method.

So final question is: Is RTL8723DS the one to blame? Maybe it's a chip with partial 4.2 implementation?

I can provide the btmon captures if necessary.

[hyx0329]

Okay I'm 99% confident that RTL8723DS is a bluetooth 4.0 chip but advertised to be "compatible" with 4.2 standard and labeled to be a 4.2 chip.