Siglent extension

doc/configuration.rst

@@ -247,8 +247,12 @@ Currently available are:
   for details.
 
 ``siglent``
-  Controls *Siglent SPD3000X* series modules via the `vxi11 Python module
-  <https://pypi.org/project/python-vxi11/>`_.
+  Controls *Siglent SPD3000X* series modules via the `PyVISA Python module
+  <https://pypi.org/project/PyVISA/>`_ (with the ``pyvisa-py`` backend).
+  In addition to switching the output on and off, this backend supports
+  reading and configuring the per-channel voltage and current limits and
+  reading the measured voltage, current and power (see the ``show`` and
+  ``config`` actions of ``labgrid-client power``).
 
 ``simplerest``
   This is a generic backend for PDU implementations which can be controlled via
@@ -2418,6 +2422,13 @@ Implements:
 Arguments:
   - delay (float, default=2.0): delay in seconds between off and on
 
+Some programmable power supplies (currently the ``siglent`` backend) additionally
+implement :any:`ProgrammablePowerProtocol`, which allows reading the measured
+voltage, current and power and configuring the voltage and current limits. These
+are exposed via the ``show`` and ``config`` actions of ``labgrid-client power``
+(see :ref:`usage-power` for details). Backends that do not implement this
+protocol simply do not provide those actions.
+
 PDUDaemonDriver
 ~~~~~~~~~~~~~~~
 A :any:`PDUDaemonDriver` controls a `PDUDaemonPort`_, allowing control of the

doc/development.rst

@@ -160,6 +160,24 @@ The minimum requirement is a call to :code:`super().__attrs_post_init__()`.
 All that's left now is to implement the functionality described by the used
 protocol, by using the API of the bound drivers and resources.
 
+Programmable Power Supplies
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Simple power drivers only implement :any:`PowerProtocol` (``on``, ``off``,
+``cycle`` and ``get``). Power supplies that can additionally report and
+configure their output implement :any:`ProgrammablePowerProtocol`, which
+extends :any:`PowerProtocol` with three methods:
+
+- ``show()`` returns a dict with the measured ``voltage``, ``amps`` and
+  ``watts`` as well as the configured ``v_limit`` and ``a_limit``.
+- ``voltage(value)`` sets the output voltage.
+- ``amps(value)`` sets the output current limit.
+
+For the :any:`NetworkPowerDriver`, these are dispatched to the configured
+backend module, which has to provide matching ``power_show``,
+``power_voltage`` and ``power_amps`` functions (see
+``labgrid/driver/power/siglent.py`` for a reference implementation).
+
 Writing a Resource
 -------------------
 

doc/usage.rst

@@ -166,6 +166,44 @@ allocated before returning.
 A reservation will time out after a short time, if it is neither refreshed nor
 used by locked places.
 
+.. _usage-power:
+
+Controlling Power
+~~~~~~~~~~~~~~~~~
+
+The ``labgrid-client power`` command (short alias ``pw``) switches a place's
+power on and off:
+
+.. code-block:: bash
+
+  $ labgrid-client -p my-place power on
+  $ labgrid-client -p my-place power off
+  $ labgrid-client -p my-place power cycle
+  $ labgrid-client -p my-place power get
+
+For programmable power supplies (currently the ``siglent`` backend of
+:any:`NetworkPowerPort`), two additional actions are available.
+
+``power config`` sets the voltage and/or current limit:
+
+.. code-block:: bash
+
+  $ labgrid-client -p my-place power config --voltage 5.0 --amps 1.5
+  set voltage to 5.0V
+  set amps to 1.5A
+
+``power show`` reads back the measured voltage, current and power together with
+the configured limits (shown in square brackets):
+
+.. code-block:: bash
+
+  $ labgrid-client -p my-place power show
+  Voltage: 5.001V [5.0V], Current: 0.209A [1.5A], Power: 1.045W
+
+The power value is read directly from the device rather than being computed from
+voltage times current, so it stays accurate even though those two values are
+sampled at slightly different times.
+
 Library
 -------
 labgrid can be used directly as a Python library, without the infrastructure

labgrid/driver/power/siglent.py

@@ -38,15 +38,30 @@ def power_show(host, port, index):
     with _get_psu(host) as psu:
         v_measured = psu.query(f"MEAS:VOLT? CH{index}")
         a_measured = psu.query(f"MEAS:CURR? CH{index}")
+        w_measured = psu.query(f"MEAS:POWE? CH{index}")
         v_set = psu.query(f"CH{index}:VOLT?")
         a_set = psu.query(f"CH{index}:CURR?")
     return {
         "voltage": float(v_measured),
         "amps": float(a_measured),
+        "watts": float(w_measured),
         "v_limit": float(v_set),
         "a_limit": float(a_set)
     }
 
+def power_watts(host, port, index):
+    """Read the power (in watts) measured by the device on the given channel.
+
+    The PSU reports true power directly, so this avoids errors from
+    multiplying voltage and current sampled at slightly different times.
+    """
+    assert port is None
+    index = int(index)
+    assert 1 <= index <= 2
+    with _get_psu(host) as psu:
+        w_measured = psu.query(f"MEAS:POWE? CH{index}")
+    return float(w_measured)
+
 def power_voltage(host, port, index, voltage):
     assert port is None
     index = int(index)

labgrid/remote/client.py

@@ -941,7 +941,6 @@ def power(self):
         from ..resource.power import NetworkPowerPort, PDUDaemonPort
         from ..resource.remote import NetworkUSBPowerPort, NetworkSiSPMPowerPort, NetworkSysfsGPIO
         from ..resource import TasmotaPowerPort, NetworkYKUSHPowerPort
-        from ..protocol import ProgrammablePowerProtocol
 
         drv = None
         try:
@@ -989,8 +988,11 @@ def power(self):
         if action == "get":
             print(f"power{' ' + name if name else ''} for place {place.name} is {'on' if res else 'off'}")
         elif action == "show":
-            res = drv.show()
-            print(f"Voltage: {res['voltage']}V [{res['v_limit']}V], Current: {res['amps']}A [{res['a_limit']}A]")
+            print(
+                f"Voltage: {res['voltage']}V [{res['v_limit']}V], "
+                f"Current: {res['amps']}A [{res['a_limit']}A], "
+                f"Power: {res['watts']}W"
+            )
 
 
     def digital_io(self):

man/labgrid-client.1

@@ -556,7 +556,8 @@ change (or get) a place\(aqs power status
 .INDENT 3.5
 .sp
 .EX
-usage: labgrid\-client power|pw [\-t DELAY] [\-\-name NAME] {on,off,cycle,get}
+usage: labgrid\-client power|pw [\-t DELAY] [\-v VOLTAGE] [\-a AMPS] [\-\-name NAME]
+                               {on,off,cycle,get,show,config}
 .EE
 .UNINDENT
 .UNINDENT
@@ -571,6 +572,16 @@ wait time in seconds between off and on during cycle
 .UNINDENT
 .INDENT 0.0
 .TP
+.B \-v <voltage>, \-\-voltage <voltage>
+voltage value to be configured
+.UNINDENT
+.INDENT 0.0
+.TP
+.B \-a <amps>, \-\-amps <amps>
+amps value to be configured
+.UNINDENT
+.INDENT 0.0
+.TP
 .B \-\-name <name>, \-n <name>
 optional resource name
 .UNINDENT

tests/test_powerdriver.py

@@ -310,13 +310,85 @@ def test_import_backend_tplink(self):
         import labgrid.driver.power.tplink
 
     def test_import_backend_siglent(self):
-        pytest.importorskip("vxi11")
+        pytest.importorskip("pyvisa")
         import labgrid.driver.power.siglent
 
     def test_import_backend_poe_mib(self):
         pytest.importorskip("pysnmp")
         import labgrid.driver.power.poe_mib
 
+    def _mock_siglent_psu(self, mocker, responses=None):
+        rm = mocker.patch("pyvisa.ResourceManager")
+        psu = rm.return_value.open_resource.return_value
+        # `with _get_psu(...) as psu` must yield the same mock we configure
+        psu.__enter__.return_value = psu
+        if responses is not None:
+            psu.query.side_effect = lambda cmd: responses[cmd]
+        return psu
+
+    def _activate_siglent_driver(self, target):
+        NetworkPowerPort(target, "power", model="siglent", host="192.0.2.1", index="1")
+        d = NetworkPowerDriver(target, "power")
+        target.activate(d)
+        return d
+
+    def test_siglent_on_off_get(self, target, mocker):
+        pytest.importorskip("pyvisa")
+
+        # CH1 output state is reported in bit 4 of the hex SYSTEM:STATUS? value
+        psu = self._mock_siglent_psu(mocker, {"SYSTEM:STATUS?": "0x0010"})
+        d = self._activate_siglent_driver(target)
+
+        d.on()
+        psu.write.assert_called_with("OUTPUT CH1,ON")
+        d.off()
+        psu.write.assert_called_with("OUTPUT CH1,OFF")
+
+        assert d.get() is True
+        psu.query.side_effect = lambda cmd: {"SYSTEM:STATUS?": "0x0000"}[cmd]
+        assert d.get() is False
+
+    def test_siglent_show(self, target, mocker):
+        pytest.importorskip("pyvisa")
+
+        self._mock_siglent_psu(mocker, {
+            "MEAS:VOLT? CH1": "5.001",
+            "MEAS:CURR? CH1": "0.209",
+            "MEAS:POWE? CH1": "1.045",
+            "CH1:VOLT?": "5.0",
+            "CH1:CURR?": "1.5",
+        })
+        d = self._activate_siglent_driver(target)
+
+        assert d.show() == {
+            "voltage": 5.001,
+            "amps": 0.209,
+            "watts": 1.045,
+            "v_limit": 5.0,
+            "a_limit": 1.5,
+        }
+
+    def test_siglent_voltage_amps(self, target, mocker):
+        pytest.importorskip("pyvisa")
+
+        psu = self._mock_siglent_psu(mocker)
+        d = self._activate_siglent_driver(target)
+
+        d.voltage(5.0)
+        psu.write.assert_called_with("CH1:VOLT 5.0")
+        d.amps(1.5)
+        psu.write.assert_called_with("CH1:CURR 1.5")
+
+    def test_siglent_power_watts(self, mocker):
+        pytest.importorskip("pyvisa")
+        from labgrid.driver.power import siglent
+
+        psu = self._mock_siglent_psu(mocker, {"MEAS:POWE? CH2": "2.5"})
+
+        # power is read from the device, not derived from voltage * current
+        assert siglent.power_watts("192.0.2.1", None, 2) == 2.5
+        psu.query.assert_called_once_with("MEAS:POWE? CH2")
+
 class TestYKUSHPowerDriver:
     YKUSH_FAKE_SERIAL = "YK12345"
     YKUSH_LIST_OUTPUT = f"Attached YKUSH Boards:\n1. Board found with serial number: {YKUSH_FAKE_SERIAL}".encode(