Ghpsdr3 protocols

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server HPSDR hardware server

The HPSDR server handles communications with the HPSDR hardware and is designed to work with multiple receivers either on a single Mercury card or multiple Mercury cards. It demultiplexes the I/Q samples into separate streams for each receiver. The hardware server listens on port 11000 for TCP connections from clients. The client (dspserver) makes a connection request through port 11000, and sets up a TCP socket on on port 12000+rx, on which it sends commands to the server. IQ data is sent over UDP.

Commands to server

The server recognizes a number of commands, shown below. It sends a response to the client after parsing each command. The possible responses are also shown.

    • attach rx
    attach client to receiver rx
    The receiver number rx is an integer from 0 to 3
    example: attach 0
    response:
    "Error: Client is already attached to receiver" (Receiver rx is already attached.)
    "Error: Invalid Receiver" (rx is higher than number of receivers specified on the command line.)
    "Error: Receiver in use"
    "OK" <sample Rate>
    • detach rx
    detach client from receiver rx
    example: detach 0
    response:
    "Error: Client is not attached to receiver"
    "Error: Invalid Receiver" (rx is higher than number of receivers specified on the command line.)
    "Error: Not owner of receiver"
    • frequency f
    Set attached receiver frequency to the integer frequency f (Hz)
    example: frequency 7056000
    response:
    "Error: Client is not attached to receiver"
    "Error: Invalid Receiver" (rx is higher than number of receivers specified on the command line.)
    "OK"
    • start iq port
    start sending I & Q samples for the attached receiver to the UDP port specified
    example: start iq 13000
    response:
    "Error: Invalid Command"
    "OK"
    • start bandscope port
    start sending bandscope samples to the UDP port specified
    example start bandscope 12500
    response:
    "Error: Invalid Command"
    "OK"
    • stop iq
    stop sending I & Q data to the attached receiver
    response:
    "Error: Invalid Command"
    "OK"
    • stop bandscope
    stop sending bandscope data
    response:
    "Error: Invalid Command"
    "OK"

A typical exchange would be:

ClientServer
attach 0OK 96000
set frequency 7056000OK
start iq 13000OK
set frequency 7056100OK
stop iqOK
detach 0OK

Note that there are currently no commands to control setting the number of receivers, preamp, dither, random, samplerate or clock sources. As this was developed to support multiple receivers, I decided to not allow clients to change these as they would be changed for all receivers. They are all controlled by command line arguments when running the server.

I / Q data stream

The I/Q samples are accumulated in the server until there are 1024 I/Q samples to send. The samples are sent in 512 byte UDP packets, to the port specified in the 'start iq' message, with 12 byte header and up to 500 bytes of I/Q samples.

The UDP packet header contains:

  • 8 byte sequence number
  • 2 byte offset within this set of samples
  • 2 byte length of samples

Following the header, the I and Q samples are sent, first 1024 float I samples, followed by 1024 float Q samples.

server command line options (default value)

  • --receivers <1..4>
  • --samplerate [48000|96000|192000]
  • --dither [off|on]
  • --random [off|on]
  • --preamp [off|on]
  • --10mhzsource [atlas|penelope|mercury]
  • --122.88mhzsource [penelope|mercury]
  • --micsource [janus|penelope]
  • --class [E|other]

Example:

./server --receivers 4 --samplerate 96000 --dither on --10mhzsource atlas

Note: As an experiment, there is also a softrockserver that supports the same protocol with the restriction that there is only one receiver and it uses the USB/si570 interface to control the frequency. The I/Q samples are taken from an Audio device specified on the command line.

dspserver

dspserver is a client to the hardware server. In turn, it is the server for another client, typically a GUI, such as jmonitor. It provides a dsp processing service using DttSP. Typically one dspserver is started for each receiver. The dspserver listens for client TCP connections on port 8000+rx. i.e. rx0 listens on 8000, rx1 listens on 8001, etc. The client sends commands to the dspserver and dspserver sends data packets to its client on this same port. The first byte of each packet sent to the client identifies the type of data in the packet.

  • 0 spectrum data
  • 1 audio data

Commands to dspserver

    • getSpectrum points
    Request points of spectrum data. The value sent for each point is an 8 bit unsigned integer. If the calculated spectrum contains more points than the client requests, adjacent points are combined, and the highest value in the group is sent.
    Example: getSpectrum 480
    • setFrequency f
    Set the receiver frequency to f, in Hz
    example: setFrequency 7056000
    • setMode mode
    mode is an integer specifying the type of demodulation
      • 0 - LSB
      • 1 – USB
      • 2 – DSB
      • 3 – CWL
      • 4 – CWH
      • 5 – FM
      • 6 – AM
      • 7 - DIGU
      • 8 - SPEC
      • 9 - DIGL
      • 10 - SAM
      • 11 – DRM
    example: setMode 0
    • setFilter low high
    Set filter cutoff frequencies
    For LSB, both frequencies are negative
    For USB, both frequencies are positive
    For AM or DSP, typically low is negative and high is positive
    example: setFilter 150 3450
    • setAGC n
    Select AGC time
      • 1 - LONG
      • 2 - SLOW
      • 3 - MEDIUM
      • 4 - FAST
    example: setAGC 3
    • setNR n
    Set noise reduction
      • 0 - off
      • 1 - on
    • setNB n
    Set noise blanker
      • 0 - off
      • 1 - on
    • setANF n
    Set automatic noise filter
      • 0 - off
      • 1 - on
    • setRXOutputGain gain
    Set receiver audio output level to the value gain
    The value is a floating point number in the range 0 to 1.
    example: setRXOutputGain 0.5
    • startAudioStream buffer size
    start sending audio data.
    buffer size is optional, and is an integer, typically 480.
    If omitted, a value of 480 is used.
    • stopAudioStream
    stop sending the audio data.

data packet format Each packet has a 48 byte header.

Byte Function
0 Packet type: 0=spectrum data; 1=audio data
1-31 Reserved
32-39 Sample rate
40-47 Meter reading
48-end spectrum or audio data

Sample rate and Meter reading numbers are in ASCII characters.

Audio data is sent as one channel of 8-bit aLaw samples at 8000 samples per second.


dspserver command line options (default value)

  • --soundcard SANTA_CRUZ, AUDIGY_2_ZS, MP3_PLUS, EXTIGY,
    DELTA_44, FIREBOX, EDIROL_FA_66, HPSDR
  • --receiver 0, 1, 2, or 3
  • --server IP address 127.0.0.1 (this is "localhost")
  • --offset ???

summary of port usage

sender type port purpose
dspserver TCP 11000 connection request to server
dspserver TCP 12000 + 2*rx commands to server
server TCP 12000 + 2*rx responses to commands
server UDP 13000 + 2*rx I & Q data to dspserver
dspserver UDP 15000 + 2*rx demodulated audio to server for Mercury headphone/speaker output
dspserver TCP 8000 + rx spectrum & alaw-encoded audio to monitor
monitor TCP 8000 + rx commands to dspserver
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