Analog I/O

The AnalogIO API provides two types of analog functionality:

Monitoring of on-board sensors, e.g. for voltages, currents, and temperatures;
Control of voltage (power) supplies, on Digilent Waveforms devices that support it.

The AnalogIO functionality, despite its name, does not overlap with the functionality of the AnalogIn and AnalogOut instruments. It cannot be used to control the analog signal outputs or to monitor the analog signal inputs.

An exception is that the AnalogOut instrument on an Analog Discovery 2 device (and perhaps some others) can be made to control the voltage sources of the device as if they were regular, low bandwidth analog output channels, by selecting an appropriate device configuration when opening the device. This feature can be useful in rare cases when a non-constant supply voltage is needed for testing. However, in most cases by far, only a static (constant) voltage is needed, and the easiest way to accomplish that is via the AnalogIO API.

Using the Analog I/O functionality

To use the AnalogIO functionality you first need to initialize a DwfLibrary instance. Next, you open a specific device. The device’s AnalogIO API can now be accessed via its analogIO attribute, which is an instance of the AnalogIO class:

from pydwf import DwfLibrary
from pydwf.utilities import openDwfDevice

dwf = DwfLibrary()

with openDwfDevice(dwf) as device:

    # Get a reference to the device's AnalogIO functionality.
    analogIO = device.analogIO

    # Use the AnalogIO functionality.
    analogIO.reset()

AnalogIO channels and nodes

The quantities that can be monitored and controlled by the AnalogIO functionality are organized in channels. Each channel can have one or more nodes.

A typical example is the USB Monitor channel of the Analog Discovery 2 device. It has 3 nodes: Voltage, Current, and Temperature, that can be used to report on these three quantities.

The USB Monitor channel is fully passive; its nodes can only be monitored. Other channels have nodes that can also be controlled, for example the Positive Supply and Negative Supply channels of the Analog Discovery 2. Those channels have two nodes each that can be controlled (Enabled and Voltage), and one node that can only be monitored (Current).

The AnalogIO.py example program enumerates the AnalogIO channels and nodes of any Digilent Waveforms device; it is recommended to study that program to understand how to use the AnalogIO functionality.

Below, by way of example, we show the channels and nodes of three Digilent Waveforms devices: the Analog Discovery 2, the Digital Discovery, and the Analog Discovery Pro.

*AnalogIO* channels and nodes of the Analog Discovery 2 device
channel	channel name	ch. label	node	node name	unit	node type
0	Positive Supply	V+	0	Enable	n/a	`Enable`
			1	Voltage	V	`Voltage`
			2	Current	A	`Current`
1	Negative Supply	V-	0	Enable	n/a	`Enable`
			1	Voltage	V	`Voltage`
			2	Current	A	`Current`
2	USB Monitor	USB	0	Voltage	V	`Voltage`
			1	Current	A	`Current`
			2	Temperature	C	`Temperature`
3	Auxiliary Monitor	Aux	0	Voltage	V	`Voltage`
3	Auxiliary Monitor	Aux	1	Current	A	`Current`
4	Power Supply	V+-	0	Limit	n/a	`Enable`

*AnalogIO* channels and nodes of the Digital Discovery device
channel	channel name	ch. label	node	node name	unit	node type
0	Digital Voltage	VDD	0	Voltage	V	`Voltage`
			1	DINPP	n/a	`Enable`
			2	DIOPE	n/a	`Enable`
			3	DIOPP	n/a	`Enable`
			4	Drive	n/a	`Current`
			5	Slew	n/a	`Enable`
			6	Clock	Hz	`Frequency`
1	Voltage Output	VIO	0	Voltage	V	`Voltage`
1	Voltage Output	VIO	1	Current	A	`Current`
2	USB Monitor	USB	0	Voltage	V	`Voltage`
2	USB Monitor	USB	1	Current	A	`Current`

*AnalogIO* channels and nodes of the Analog Discovery Pro (ADP3450) device
channel	channel name	ch. label	node	node name	unit	node type
0	Digital Voltage	DVCC	0	Voltage		`Voltage`
			1	DIOPE	n/a	`Enable`
			2	DIOPP	n/a	`Enable`
1	Zynq	Zynq	0	Temperature	C	`Temperature`
			1	VccInt	V	`Voltage`
			2	VccAux	V	`Voltage`
			3	VccBRam	V	`Voltage`
			4	VccPInt	V	`Voltage`
			5	VccPAux	V	`Voltage`
			6	VccDDR	V	`Voltage`
2	ZynqMin	ZynqMin	0	Temperature	C	`Temperature`
			1	VccInt	V	`Voltage`
			2	VccAux	V	`Voltage`
			3	VccBRam	V	`Voltage`
			4	VccPInt	V	`Voltage`
			5	VccPAux	V	`Voltage`
			6	VccDDR	V	`Voltage`
3	ZynqMax	ZynqMax	0	Temperature	C	`Temperature`
			1	VccInt	V	`Voltage`
			2	VccAux	V	`Voltage`
			3	VccBRam	V	`Voltage`
			4	VccPInt	V	`Voltage`
			5	VccPAux	V	`Voltage`
			6	VccDDR	V	`Voltage`

Note

Channel 2 (ZynqMin), node 5 of the Analog Discovery Pro device was reported incorrectly in version 3.16.3 of the DWF library. This has been corrected in version 3.17.1.

AnalogIO reference

class AnalogIO

The AnalogIO class provides access to the analog I/O functionality of a DwfDevice.

The AnalogIO methods are used to control the power supplies, reference voltage supplies, voltmeters, ammeters, thermometers, and any other sensors on the device. These are organized into channels which contain a number of nodes. For instance, a power supply channel might have three nodes: an ‘enable’ setting, a voltage level setting/reading, and current limitation setting/reading.

Attention

Users of pydwf should not create instances of this class directly.

It is instantiated during initialization of a DwfDevice and subsequently assigned to its public analogIO attribute for access by the user.

reset() → None

Reset and configure all AnalogIO settings to default values.

If autoconfiguration is enabled, the changes take effect immediately.

Raises:: DwfLibraryError – An error occurred while executing the reset operation.

configure() → None

Configure the AnalogIO functionality.

This method transfers the settings to the Digilent Waveforms device. It is not needed if autoconfiguration is enabled.

Raises:: DwfLibraryError – An error occurred while executing the configure operation.

status() → None

Read the status of the device and stores it internally.

The status inquiry methods that follow will return the information that was read from the device when this method was last called.

Note that the AnalogIO functionality is not managed by a state machine, so this method does not return a value.

Raises:: DwfLibraryError – An error occurred while executing the status operation.

enableInfo() → Tuple[bool, bool]

Verify if Master Enable and/or Master Enable Status are supported.

The Master Enable is a software switch that enable the AnalogIO voltage sources.

If supported, the current value of this Master Enable switch (Enabled/Disabled) can be set by the enableSet() method and queried by the enableGet() method.

The Master Enable Status that can be queried by the enableStatus() method may be different from the Master Enable value if e.g. an over-current protection circuit has been triggered.

Returns:: The tuple elements indicate whether Master Enable Set and Master Enable Status, respectively, are supported by the AnalogIO device.
Return type:: Tuple[bool, bool]
Raises:: DwfLibraryError – An error occurred while executing the operation.

enableSet(master_enable: bool) → None

Set value of the Master Enable setting.

Parameters:: master_enable (bool) – The new value of the Master Enable setting.
Raises:: DwfLibraryError – An error occurred while executing the operation.

enableGet() → bool

Return the current value of the Master Enable setting.

Returns:: The value of the Master Enable setting.
Raises:: DwfLibraryError – An error occurred while executing the operation.

enableStatus() → bool

Return the actual Master Enable Status value (if the device supports it).

The Master Enable Status value may be different from the Master Enable setting if e.g. an over-current protection circuit has been triggered.

Returns:: the current status of the Master Enable circuit.
Return type:: bool
Raises:: DwfLibraryError – An error occurred while executing the operation.

channelCount() → int

Return the number of AnalogIO channels available on the device.

Returns:: The number of AnalogIO channels.
Return type:: int
Raises:: DwfLibraryError – An error occurred while executing the operation.

channelName(channel_index: int) → Tuple[str, str]

Return the name (long text) and label (short text, printed on the device) for the specified AnalogIO channel.

Parameters:: channel_index (int) – The channel for which we want to get the name and label.
Returns:: The name and label of the channel.
Return type:: Tuple[str, str]
Raises:: DwfLibraryError – An error occurred while executing the operation.

channelInfo(channel_index: int) → int

Return the number of nodes associated with the specified AnalogIO channel.

Parameters:: channel_index (int) – The channel for which we want to get the number of associated nodes.
Returns:: The number of nodes associated to the channel.
Return type:: int
Raises:: DwfLibraryError – An error occurred while executing the operation.

channelNodeName(channel_index: int, node_index: int) → Tuple[str, str]

Return the node name (“Voltage”, “Current”, …) and units (“V”, “A”, …) for the specified AnalogIO node.

Parameters:

channel_index (int) – The channel for which we want to get the name and unit.
node_index (int) – The node for which we want to get the name and unit.

Returns:

The name and unit of the quantity associated with the node.

Return type:

Tuple[str, str]

Raises:

DwfLibraryError – An error occurred while executing the operation.

channelNodeInfo(channel_index: int, node_index: int) → DwfAnalogIO

Return the type of physical quantity (e.g., voltage, current, or temperature) represented by the specified AnalogIO channel node.

Parameters:

channel_index (int) – The channel for which we want to get the type of physical quantity.
node_index (int) – The node for which we want to get the type of physical quantity.

Returns:

The type of physical quantity represented by the node.

Return type:

DwfAnalogIO

Raises:

DwfLibraryError – An error occurred while executing the operation.

channelNodeSetInfo(channel_index: int, node_index: int) → Tuple[float, float, int]

Return the limits of the value that can be assigned to the specified AnalogIO channel node.

Since a node can represent many things (power supply, temperature sensor, etc.), the minimum, maximum, and steps parameters also represent different types of values.

The channelNodeInfo() method returns the type of values to expect and the channelNodeName() method returns the units of these values.

Parameters:

channel_index (int) – The channel for which we want to get the currently configured value.
node_index (int) – The node for which we want to get the currently configured value.

Returns:

The minimum and maximum values for the specified node’s value, and the number of resolution steps.

Return type:

Tuple[float, float, int]

Raises:

DwfLibraryError – An error occurred while executing the operation.

channelNodeSet(channel_index: int, node_index: int, node_value: float) → None

Set the node value for the specified AnalogIO channel node.

Parameters:

channel_index (int) – The channel for which we want to set the value.
node_index (int) – The node for which we want to set the value.
node_value (float) – The value we want to set the node to.

Raises:

DwfLibraryError – An error occurred while executing the operation.

channelNodeGet(channel_index: int, node_index: int) → float

Return the current value of the specified AnalogIO channel node.

Parameters:

channel_index (int) – The channel for which we want to get the current value.
node_index (int) – The node for which we want to get the current value.

Raises:

DwfLibraryError – An error occurred while executing the operation.

channelNodeStatusInfo(channel_index: int, node_index: int) → Tuple[float, float, int]

Return the range of status values for the specified AnalogIO channel node.

Parameters:

channel_index (int) – The channel for which we want to get status information.
node_index (int) – The node for which we want to get status information.

Returns:

The minimum and maximum status values for the specified node, and the number of resolution steps.

Return type:

Tuple[float, float, int]

Raises:

DwfLibraryError – An error occurred while executing the operation.

channelNodeStatus(channel_index: int, node_index: int) → float

Return the most recent status value reading of the specified AnalogIO channel node.

To fetch updated values for all AnalogIO nodes, use the status() method.

Returns:: The most recent value read for this channel node.
Return type:: float
Raises:: DwfLibraryError – An error occurred while executing the operation.

property device

Return the DwfDevice instance of which we are an attribute.

This is useful if we have a variable that contains a reference to a DwfDevice attribute, but we need the DwfDevice itself.

Returns:: The DwfDevice instance that this attribute belongs to.
Return type:: DwfDevice