[I hope I won't be thought too 'pushy' if I point out that there has been no acknowledgement or response to this query posted a week ago. I realise that everyone is a volunteer and already busy, but other queries raised at the same time were acknowledged - perhaps it got lost as noise, or to be done later... ]
May I propose a new candidate device for support by sigrok.
The 'pcbscope' available from picaxe.com. http://www.picaxe.com/Hardware/Add-on-Modules/PCB-scope/
The pcbscope is a bare-board device using smd manufacture, based on the
same developer's earlier DPScopeSE. Both are usb-connected, using HID
(not serial emulation) as the data transfer mechanism. The device has a
webpage here - http://www.pdamusician.com/dpscope/overview_se.html
The software needed to exploit dpscopese/pcbscope is available only
for Windows, but the developer has provided documentation on the API,
available here - http://www.pdamusician.com/dpscope/files/DPScope_SE_Interface_Description.pdf
I would be prepared to donate a pcbscope to the sigrok developers to encourage this development.
Regards - David Roberts