Recommendations for Raspberry Pi
This post is preliminary, I have not tested all the rPi4 permutations yet. My initial version of this post confused 3B and 3B+ 
This post summarizes how to connect multiple FUNcube dongles to Raspberry Piās. If you will deploy many FCDs a Pi3B is recommended over a Pi4B because it has a Multi-TT hub for its 4 ports while the Pi4B has a Single-TT hub (see previous post for details).
The bottom line: each FCD needs a TT (Transaction Translator, i.e., USB1.1->USB2 accelerator). A Single-TT hub can thus support one FCD, a Multi-TT hub can support one on each of its ports.
Recommendations
- the total number of FCDs probably shouldnāt exceed 4, at least itās untested territory
- rPi3B/3B+: connect 4x FCDs to all four ports (but then no ports are left for CTT radios, GPS, cell modem, etc)
- rPi3B/3B+: connect 3x FCDs to three ports and a hub to the 4th port
- rPi4B: connect one FCD to one of its ports, that will use the rPiās single TT
- if a Multi-TT hub is connected each of its ports can have an FCD, this the best especially for rPi4B, but Multi-TT hubs are not easy to find anymore
- if a 4-port Single-TT hub is connected then it can have one FCD (plus other devices)
- if a 7-port Single-TT hub is connected it most likely can have two FCDs (plus other devices) if the hub consists of two stacked 4-port hubs and the two FCDs are plugged one into the āupperā hub and the other into the ālowerā hub
- the USB ports on the rPi can support 1.2A total, 4x FCDs use ~700mA, 1x RTL-SDR appears to use ~200mA so a powered hub may be required depending on configuration
I have successfully plugged 4x FCDs + 1x RTL-SDR + 1x CTT radio into an rPi3B, including 2xFCDs + RTL-SDR + CTT radio into a 7-port Single-TT hub.
Tools
- the Sensorgnome V2 softwareās radio tab shows the sample rate: it needs to remain pegged to 48kHz for all FCDs & RTL-SDRs
- the port mapping pane shows the āport pathā where each level corresponds to a hub, so 1.2 is port 2 of the root hub (1), 1.5.3 is port 3 of a hub in port 5 of the root hub, and 1.5.4.2 means there are two stacked hubs (e.g. 7-port hub)