Add HelixPico keyboard

[MakotoKurauchi]

I added a new HelixPico keyboard

[drashna]

Thanks!

[drashna]

Also, don't know if you saw it, but a "split common" feature was added recently. Where all of the split code is maintained as part of the core code.

https://docs.qmk.fm/#/config_options?id=feature-options

[MakotoKurauchi]

I did not know that option. Thank you.

[mtei]

Hi,
There was a bug in serial.c of let's split and serial.c of helix before commitID 1038bbe.
Therefore, quantum/split_common/serial.c also has a bug.

In Helix keyboard(include HelixPico, I think), left and right hand communication was unstable when long cable was used.
The reason is that sync_send () and sync_recv () are improperly used when sending data from master to slave and can not be synchronized.

I think that you can be convinced by looking at the image of the third piece of this tweet.
https://twitter.com/mtei/status/1010807503024619520

Helix keyboard is transmitting 5 bytes from master to slave, so the effect of this bug was significant.

[mtei]

Previously, I fixed a bug in helix serial.c and contributed it to Makoto Kurauchi.
( 1038bbe )

And now I am sending a new pull-request to Makoto Kurauchi.
( MakotoKurauchi#14 )

I hope that this latest serial.c will be used on other keyboards as well.