Hasu USB to USB Converter Questions

I’ve been mulling over picking one up for a while now, but was curious as to it’s limitations. For those of you who have used / are using one, I call upon your collective wisdom. I know internal keycodes that don’t make it out of the native controller are a no-go such as function keys. I’m more concerned with having the same programmability as my other QMK PCBs. For instance, can you use advanced features like OSL and SpaceCadet Shift? I typically use my caps lock as Ctrl when held, caps lock when tapped – would this feature be possible on the Hasu Converter? Thanks in advance for your input.

1 Like

I’ve used one with a Realforce 87U and CoolerMaster MasterKeys Pro S. As you noted, keycodes that are handled on the board (like Fn lighting controls on the MasterKeys) won’t be passed through the Hasu converter, and so they can’t be reprogrammed, since the Hasu controller will never see the keycode. Otherwise, I’ve found them to be just as programmable as any other QMK-supported PCB. While I don’t use the specific features you mentioned, I do mod-tap mappings on the Alt keys for all of my boards, as well as a few SEND_STRING macros on a different layer - and those all work on the Hasu controller.

The one limitation I’ve run into is that it doesn’t support NKRO boards (for example, the Realforce R2 PFU limited edition). As I understand it, the issue is that NKRO is not standardized across boards/manufacturers, so in order for the USB conversion to happen, there has to be a translation from the specific keyboard’s NKRO keycodes to the 6KRO keycode that the Hasu controller will send to the host PC. I think Hasu indicated that it’s theoretically possible to do this by writing a HID report parser for your specific keyboard, but that’s beyond my TMK/QMK skill level at the moment.


Correct only 6 key roll over is supported, and obviously keys which do not trigger a keycode on the USB port cannot be reprogrammed.
I used a Arduino Leonardo based TMK (no soldering required!) usb2usb controller for a while and it’s really a great way to get into fully programmable keyboards.


Maybe you got this answer already but

Yes, I use the caps lock as layer function key when held, caps lock when tapped with the usb2usb and my novatouch :+1:
I use space in a similar way with another layer, and have used custom shifted keys, you can do a lot with it actually, a lot of the QMK functionality comes from TMK. Not sure about OSL or SpaceCadet Shift, I haven’t used those