usb module#

USB Protocol#

This package contains the definitions for the Universal Serial Bus protocol.

`https://en.wikipedia.org/wiki/USB`_ `https://www.usb.org/`_

Transport vs Connector Bundles#

The USB protocol contains many different layers from physical to logical. The bundles in this package are organized to support two levels in the application:

Transport - This is the set of signals that convey the information in the bus. These signals typically traverse many components from the connector to the processor endpoint.

These signals typically have SI constraints attached to them.

Connector - This is the physical layer where the USB cable meets the board. This interface may have power, shield, and other accessory pins in addition to the transport layer signals. These additional connections may or may not make there way to the processor endpoint.

In the code below, the “transport” bundles are what you would typically use when connecting up the different modules of your circuit. The “connector” bundles are typically used to define the ports on a physical connector component or module that contains the physical connector component.

Symmetry in Transport Bundles#

If you look closely at the bundles defined below, you will notice some symmetry in the definitions of the transport bundles.

The USBData bundle defines the USB2.0 interface with port data. This same interface gets reused in USBSuperSpeed and USB_C later on.

Similarly, we use lane to define an array of LanePair` bundles (RX + TX differential pairs). This same pattern gets used in USB_C.

This is not by accident. The reason we structure the bundles this way is:

They can easily used in provide/require pin assignment statements.

We can simplify the implementation of the connect, constrain, and routing structure application functions.

Matching Lanes#

For most of the constraint functions in this package, the bundle types themselves are not checked for equality. Instead - we check for matching lane configurations. This allows a USBSuperSpeed and USB_C transport bundle to connect to each other if they have the correct number of lanes defined.

class USB2[source]#

Bases: Port

Transport Bundle for the USB 2.0 Interface

data = DiffPair()#: Differential pair for USB data

class USB2Connector[source]#

Bases: Port

Connector Bundle for the USB 2.0 Interface

vbus = Power()#: Power bundle for USB connector interface

bus = USB2()#: USB2 bundle (differential pair)

id = Port()#: ID signal

class USBSuperSpeed(lane_count=2)[source]#

Bases: USB2

Transport Bundle for Superspeed USB

This bundle supports USB 3/4 transport signals. These are the signals that are typically connected with SI constraints from the connector to the MCU or other components.

This bundle type is usually used to construct the ports on MCUs, ESD devices, Muxes, etc in the USB 3/4 applications.

Parameters:: lane_count – Number of superspeed lanes in this bundle.

lane: Sequence[LanePair]#: A configurable number of lane-pairs for data transfer

class USBSuperSpeedConnector[source]#

Bases: Port

Connector Bundle for USB Type A SuperSpeed™ Connectors

vbus = Power()#: Power bundle for USB connector interface

bus = USBSuperSpeed()#: USBSuperSpeed bundle for high speed data transfer

shield = Port()#: Pin for connection to cable shield

class USB_C(lane_count=2)[source]#

Bases: USBSuperSpeed

Transport Bundle for USB3/4

Parameters:: lane_count – Number of superspeed lanes in this bundle.

cc = (Port(), Port())#: CC pins for capability identification

sbu = (Port(), Port())#: SBU pins for side band utility

class USB_C_Connector[source]#

Bases: Port

Connector Bundle - USB Type C Connector

This bundle is typically applied to a physical connector component in a board design.

vbus = Power()#: Power bundle for USB connector interface

bus = USB_C()#: USB_C bundle for high speed data transfer

shield = Port()#: Pin for connection to cable shield

class USBStandard(skew, impedance)[source]#

Parameters:

skew (Toleranced)
impedance (Toleranced)

skew: Toleranced#

impedance: Toleranced#

loss = 12.0#

Constraint(structure: DifferentialRoutingStructure | None = None)[source]#

Construct a SignalConstraint applicable to USB topologies of this standard.

Parameters:

std (USBStandard)
structure (DifferentialRoutingStructure | None)

class USB(skew, impedance)[source]#

Bases: USBStandard, Enum

v2 = USBStandard(skew=Toleranced(0, 3.75e-12, 3.75e-12), impedance=Toleranced(90, 13.5, 13.5))#

v3 = USBStandard(skew=Toleranced(0, 1e-12, 1e-12), impedance=Toleranced(90, 13.5, 13.5))#

v4 = USBStandard(skew=Toleranced(0, 1e-12, 1e-12), impedance=Toleranced(85, 9, 9))#