Karl-Heinz Schweikert found commands to control the board via USB serial port.
I copy his post here:
Here the secret of USB serial control:
Baud:115200, Data:8, Stop:1, Parity:none, Type:Hex, Send on Enter:none
Point: send 11 bytes B0..B10
with B0:ad; B1:01=ADF4350,02=ADF4351; B2:01=point; B3:01=0dB,02=-3dB,03=-6dB,04=-9dB
B4-6:fRef (03 d0 90 = 25.0000 MHz); B7-9:fPoint (03 0d 40 = 200.000 MHz); B10:sum(B0..9) & 255
Stop: send 3 bytes B0..B2
with B0:ad; B1:ff; B2=ac
Sweep: send 18 bytes B0..B17, with B2:02=sweep; (others same as Point)
B7-9:Start; B10-12:Stop; B13-15:Step; B16:01=kHz,02=MHz; B17:sum(B0..16) & 255
Return on success: ad 66 13
Example:
ad 02 01 01 03 d0 90 00 88 b8 54 = ADF4350,Point,0dB,fRef=25.0000,f=35.000
ad ff ac = Stop
ad 02 02 01 03 d0 90 0a ae 60 0c 35 00 00 13 88 02 0b = ADF4351,Sweep,0dB,fRef=25.0000,f=700.000..800.000MHz, Step 5.000MHz
Nice to use a small Python script to set a defined frequency, and e.g. read a filter response with logarithmic RF detector+Arduino, before switching to next frequency. Mixed operation with remote und manual works fine.