Notes on ITango Usage

Here we present a basic usage of FPGA methods from ITango shell.

Device Setup

Once ITango shell is open (e.g. from k9s console) we need to create a proxy device:

In [1]: dev = Device("low-cbf/processor/0.0.0")

Next, we’ll download a personality from the registry - either CAR (Nexus) for released personality versions - or GitLab for development versions. However as this download can take longer than the default ITango command timeout, we first extend the timeout value:

In [2]: dev.set_timeout_millis( 12_000 )

In [3]: dev.SelectPersonality('{ "personality": "cnic", "version":"0.1.2-dev.a9cbe", "source": "gitlab"}')

We bring the device online with:

In [4]: dev.adminMode=0

In [5]: dev.adminMode
Out[5]: <adminMode.ONLINE: 0>

Calling Methods

In general there are two kinds of methods we can call from ITango shell:

top level methods on the device itself
the methods on one of constituent ‘peripherals’

As Tango commands could only accept a single argument, we need to pack into it all the details of the called function - the function name, all function arguments (if any) and, optionally, the ‘peripheral’ name if applicable. All this information is stored in a JSON string with the structure along these lines:

{ 
  "peripheral" : "peripheral_name", 
  "method":    "method_name", 
  "arguments": 
  { 
    "arg1_name": value1,
    "arg2_name": value2,
    ...
  }
}

So in order to call dump_cap() method on hbm_pktcontroller peripheral, in ITango shell we would type:

In [6]: dev.CallMethod('{ "peripheral" : "hbm_pktcontroller", "method": "dump_pcap", "arguments": { "out_filename" : "zulu.pcap", "packet_size": 128}}')
Out[6]: [array([0], dtype=int32), ['OK']]

or to call the top level method (i.e. not bound to a peripheral) transmit_pcap()

In [7]: dev.CallMethod('{ "method": "transmit_pcap", "arguments": { "in_filename" : "spead-5a.pcap"}}')
Out[7]: [array([0], dtype=int32), ['OK']]

A More Realistic Scenario

The previous section was mostly focused on illustrating how to convert the function names and arguments into JSON format accepted by Tango infrastructure.

Here we present a possibly more useful example where in one ITango shell we start a packet receiver and in the other we initiate transmission of data packets stored in pcap format.

The reciever

dev = DeviceProxy("low-cbf/processor/0.0.0")
dev.CallMethod(‘{“method”: “receive_pcap”, “arguments”: {“out_filename”: "/test-data/outputfile.pcap"}}’)
while not dev.finished_receive:
    sleep(5)
print("Finished receiving pcap!")

A separate transmitter ITango shell:

dev = DeviceProxy("low-cbf/processor/0.0.0")
dev.CallMethod(‘{“method”: “transmit_pcap”, “arguments”: {“in_filename”: "/test-data/inputfile.pcap", "rate": 25}}’)