DDS COMB PROTOCOLS FOR THE HOST
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********** HOST IP DESCRIPTION **********
- IP is DHCP and UDP on port 37829
- After cold boot, first host to connect is the only one the unit will accept commands from, until reboot
- Host sends commands as listed below, unit asynchronously responds if required
- Every second or so, host sends a heartbeat and the unit echoes it, harmless if not sent
- All command parameters are numeric ASCII, integers, no commas or signs, space delimited
- invalid commands are ignored (e.g. wrong command length, outside range, etc)


********** HOST COMMANDS **********
===================================
CMD Size Description
-----------------------------------
 H   1      Heartbeat, echoed by unit so both know still connected
 V   1      Request Rabbit version code
 R   1      Reset channels' absolute phases now*
 F   7-13   Set the fixed Frequency, in Hz, 0.03-175MHz
              byte #1: "F"
                   #2: "A", "B", "C" or "D", the channel
                   #3: [space]
                   1-9: frequency in Hz
                   #last: [space]
              Example: "FC 123456789 " is set ch-C to 123.456789MHz
 A   5-7    Set the Amplitude, 0-100%
              byte #1: "A"
                   #2: "A", "B", "C" or "D", the channel
                   #3: [space]
                   1-3: normalized amplitude in percent
                   #last: [space]
              Example: "AB 50 " is set ch-A to half amplitude
 P   5-7    Set the Phase lead, 0-359° relative to itself
              byte #1: "P"
                   #2: "A", "B", "C" or "D", the channel
                   #3: [space]
                   1-3: phase in degrees
                   #last: [space]
              Example: "PA 10 " is set ch-A ahead by 10°
 S   25-39  Sweep The Frequency
              byte #1: "R"
                   #2: "A", "B", "C" or "D", the channel
                   #3: [space]
                   1-9: High freq, in Hz, 10-175MHz, must be higher than low f
                   1: [space]
                   1-9: Low freq, in Hz, 10-175MHz, must be lower than high f
                   1: [space]
                   1-9: Step size, in Hz, 1Hz-175MHz
                   1: [space]
                   1-5: Step time, in nS, 4-65000nS, rounded to 4nS increments
                   #last: [space]
              Example: "SD 123400000 101000000 15000 2000 " means sweep ch-D between 123.4MHz and 101MHz, stepping 15KHz every 2uS.
 U   5-7    Ramp the output amplitude up and down, 0-255uS (0=no ramp)
              byte #1: "U"
                   #2: "A", "B", "C" or "D", the channel
                   #3: [space]
                   1-3: ramp time in uS
                   #last: [space]
              Example: "AU 123 " is ramp ch-A amplitude up and down in 126uS, using the CH-A TTL input.

*NOTE ON "R": Each channel's phase is relative to itself, the R command will reset phase differences between channels,
              however this only works for identical frequencies and is exclusive of the set phase offset.



********** UNIT RESPONSES **********
====================================
RES Size Description
-----------------------------------
 H   1   Heartbeat
 I   37  IP address of a unit without a host
           byte #1: "I"
                #2: Type identifier (e.g. "C" for DDS Comb)
                #3-22: Unit name
                #23-37: Unit's IP address
 V   >2  Version (in ASCII)
           byte #1: "V"
                #2-21: Rabbit version string

********** UNIT RESPONSE EXAMPLES **********
"H" = heartbeat, unit is alive and well and living in Toronto
"V1.2.3" means Rabbit version is 1.2.3
"ICDDS Comb #1         192.168.1.101  " means 'DDS Comb #1' on 192.168.1.101 is looking for a host