[TangerineSDR] PSWS System Specification preliminary Ver 0.1

[Scotty Cowling]

Hi Tom,

Here are my comments on your excellent document.

73,
Scotty WA2DFI

Notes on PSWS Specification V 0.1 5 May 2019

Section 3.0
Clock module will have 4 *programmable clock* outputs:
1. FPGA
2. RF Module #1
3. RF Module #2
4. High-speed Reference Clock

In addition, two more outputs:
5. 1 PPS timing
6. 10MHz fixed reference

Clock outputs should be differential LVDS. Single ended clocks will be 
too noisy, especially across a connector boundary.

The FPGA should not provide the ADC clocks, they should come directly 
from the clock module. The ADC may supply a source-synchronous data 
clock to the FPGA.

Section 4.0
Magnetometer interface can be I2C, SPI, serial UART or RS-485.

The magnetometer will almost certainly need to be remotely mounted. In 
this case, RS-485 is recommended. We can specify two-wires for 
communictions and two wires for power (typically 5V).

Section 5.0
It is not immediately clear that *each* RF Module has two synchronous 
channels.

Note that the *pluggable filter* can be bypassed with a jumper, making 
it optional. Maybe call it "optional pluggable filter".

Section 6.
The DE shall also be capable of sourcing or sinking UDP data streams 
to/from any IP address, under direction of the host processor.

The DE will have a three-port GbE switch, connecting the FPGA, host PC 
and external network. How do you want to explain this?

Section 7.0
Processing the stream from the DE is optional, since it may not be able 
to process this much data. The metadata tasks will fall to the DE in 
this case.

The host will not always transmit the data to the central server. The 
host may direct the DE to stream data directly to the central server if 
it cannot process the volume or rate of data.

Section 8.
I have been using "Command and Control Protocol" for the protocol used 
between the central server and the host PC. I have been using "Local SDR 
Protocol" for the protocol between the host PC and the DE.

We could use "Remote Command and Control", or "RCC" for the 
host<-->central server communications, and "Local Command and Control" 
or "LCC" for host<-->DE communications. Whatever we use, we should 
define it.

The Remote Command and Control section seems to be missing (although you 
refer to it once in section 10). Even though we don't know what the 
protocol    is, I think it should be mentioned (as defined an a separate 
document?)

I think we need to make a clear distinction between Remote C&C and Local 
SDR C&C. We will need security and maybe encryption on the Remote C&C, 
but not so much on the Local SDR protocol.