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Comedi

Prerequisites​

This node-type requires comedilib (>= 0.11.0).

Implementation​

The source code of the node-type is available here: https://github.com/VILLASframework/node/blob/master/lib/nodes/comedi.cpp

Configuration​

subdevice
integer
bufsize
integer
Default: 16
required
Array of objects (comedi_signal)
rate
required
integer
object (Input configuration (received by VILLASnode))
vectorize
integer
Default: 1

This setting allows to send multiple samples in a single message to the destination nodes.

The value of this setting determines how many samples will be combined into one packet.

Array of Hook Object (object) or Hook Name (string) (hook_list)
builtin
boolean (Builtin hook functions)
Default: true

By default, each node and paths has a couple of default hooks attached to them. With this setting the attachment of built-in hooks can be disabled.

object (Output configuration (sent out by VILLASnode))
{
  • "subdevice": 0,
  • "bufsize": 16,
  • "signals": [
    ],
  • "rate": 0,
  • "in": {
    },
  • "vectorize": 1,
  • "hooks": [
    ],
  • "builtin": true,
  • "out": {
    }
}

Example​

node/etc/examples/nodes/comedi.conf
nodes = {
    pcie6259 = {
        type = "comedi"

        device = "/dev/comedi0"
        in = {
            subdevice = 0
            rate = 1000

            signals = (
                # Note: order in this array defines order in villas sample
                { channel = 0, range = 0, aref = 0, name = "temperature_int" },
                { channel = 1, range = 0, aref = 0, name = "loopback_ao0" },
                { channel = 2, range = 0, aref = 0, name = "loopback_ao1" },
                { channel = 3, range = 0, aref = 0, name = "bnc_ext" }
            )
        }
        out = {
            subdevice = 1
            # Note: buffer size and rate shouldn't be changed at the moment
            # output sample rate
            rate = 40000
            # Comedi write buffer in kilobytes
            bufsize = 24

            signals = (
                # Note: order in this array corresponds to order in villas sample
                { name = "ao0", channel = 0, range = 0, aref = 0 },
                { name = "ao1", channel = 1, range = 0, aref = 0 },
                { name = "ao2", channel = 2, range = 0, aref = 0 },
                { name = "ao3", channel = 3, range = 0, aref = 0 }
            )
        }
    }

    remote = {
        type = "socket"
        layer = "udp"
        format = "protobuf"

        in = {
            address = "*:12000"
        }

        out = {
            address = "134.130.169.32:12000"
        }
    }

    sine1 = {
        type = "signal"

        signal = "sine"
        values = 1
        frequency = 50
        rate = 10000
    }

    sine2 = {
        type = "signal"

        signal = "sine"
        values = 1
        frequency = 100
        rate = 10000
    }
}

paths = (
    # 2-ch sine
    # {
    #   in = [ "sine1.data[0]", "sine2.data[0]" ]
    #   out = "pcie6259"
    #   rate = 10000
    #   mask = ()
    # }

    # Remote data via UDP
    {
        in = "remote.data[0-3]"
        out = "pcie6259"
        rate = 40000
        mask = ()
    }
)

Further reading​

Linux Control and measurement device interface​

The Comedi project develops open-source drivers, tools, and libraries for data acquisition.