Embedded Systems Architecture Class Project

USB 2.0 Function ControllerDecember 12, 2008

Brandon Wolfe, Ben Marrou, Daniel Chan

Contents

• Project Objectives

• USB Overview

• Hardware Implementation

• Software Driver Implementation

Project Objectives

• Configure USB 2.0 Function Controller from opencores.org to use on lab FPGA board.

• Develop a low-level driver to initialize USB 2.0 Function Controller registers.

• Implement driver functions to allow basic communication with a USB host.

USB Overview

• USB Version 1.0– Low Speed (1.5 Mb/s)– Full Speed (12 Mb/s)

• USB Version 2.0– High Speed (480 Mb/s)

• USB Version 3.0– Super Speed (5 Gb/s)

Transfer Data Types• Control

– Configure, Get information, Status.– Small data transfers.– Endpoint 0.

• Interrupt– Small data, fixed rate.– For devices needing guaranteed response time.– Ex: Mice, Keyboard.

• Bulk– Large amounts of data, up to bus bandwidth.– Guaranteed data delivery, but not speed.– Ex: Scanners, Storage, Network devices.

• Isochronous– Large amounts of data.– Guaranteed speed, but not data delivery.– Ex: Audio, Video.

USB Descriptors

• Device – Includes USB revision, product and vendor IDs examples: fax/scanner/printer device

• Configuration – The state of the device examples: active, sleep

• Interface – Performs a feature of the device examples: scan function, print function

• Endpoint – Specifies the type of data transfer (pipes) examples: control, bulk

USB Descriptor Example

Fax/Scanner/Printer

Active Sleep

Scan Print

Control Bulk Control Bulk

Device:

Configuration:

Interface:

Endpoint:

(0) (0)(1) (1)

USB Connectors

• Series “A”– plug (upstream)– receptacle (downstream)

• Series “B”– plug (downstream)– receptacle (upstream)

• Series “mini-B”– plug (downstream)– receptacle (upstream)

USB Block Diagram

• USB Function Controller - management of data/control message flow

• PHY - link between digital logic and analog bus

Driver

Microcontroller

USB 2.0FunctionController

(peripheral)

USB PHY “mini-B”ULPI

D+

D-

Major hardware Components:• As implemented in RTL from USB Opencore

• Additional implemented RTL • Register R/W• Memory R/W• ULPI-to-UTMI Wrapper

Hardware Implementation

RTL from USB Opencore• Clock Domain 1 : 60Mhz• Clock Domain 2 : 100Mhz

Hardware Implementation cont.

Reference: opencores.org

Register R/W

Registers

Memory R/W

Memory

Reference: opencores.org

Memory R/W

Memory cont.

ULPI-to-UTMI Wrapper

# -------------------------------------------------------------------------# USB# -------------------------------------------------------------------------# NET USB_IO0 LOC = E22;# NET USB_IO1 LOC = D22;# NET USB_IO2 LOC = C22;# NET USB_IO3 LOC = D21;# NET USB_IO4 LOC = C21;# NET USB_IO5 LOC = D20;# NET USB_IO6 LOC = D19;# NET USB_IO7 LOC = C19;NET "PHY_CLK" LOC = "D18";NET "PHY_STP" LOC = "C18";NET "PHY_DIR" LOC = "D17";NET "PHY_NXT" LOC = "C17";NET "PHY_RESET" LOC = "E17";

PHY Interface

ULPI-to-UTMI Wrapper

PHY Interface cont.

Reference: SMSC

ULPI-to-UTMI Wrapper

PHY Interface cont.

Reference: SMSC

ULPI-to-UTMI Wrapper

PHY Interface cont.

Reference: USB in a NutShell

Revised Intentions for Software

1. Develop low-level driver to initialize USB Function Controller registers.

2. Implement driver functions to register USB driver with Linux USB core.

3. Understand (and implement) additional USB driver structures and functions.

USB Function Controller Driver

• Register Initialization

• USB Driver Registration

• USB Driver Communication

• USB Driver Deregistration

Significant Registers

ENDPOINT REGISTERS

Name Offset Width Access Description

EP0_CSR 40 32 RW Endpoint 0: CSR

EP0_IMS 44 32 RW Endpoint 0: Interrupt Mask Register

EP0_BUF0 48 32 RW Endpoint 0: Buffer Register 0

EP0_BUF1 4c 32 RW Endpoint 0: Buffer Register 1

EPx Registers Exist for each Endpoint (0 – 16)

GLOBAL REGISTERSName Offset Width Access Description

CSR 0 8 RW Control/Status Register FA 4 8 RW Function Address INT_MSK 8 32 RW Interrupt Mask for Endpoint Independent Sources INT_SRC C 32 ROC Interrupt Source Register FRM_NAT 10 32 RO Frame Number and Time (SOF)

Reference: opencores.org

Core Register Descriptions

• CSR– Primary configuration and status register for USB

core.

• Function Address (FA)– Set by exchanging control and status information

with host.

• INT_MSK – Interrupt mask register controls function of interrupt

pins.

• FRM_NAT – Frame number and time register, tracks frame

number/time received from SOF.

Endpoint Register Descriptions

• EPx_CSR – Endpoint control and status register, specify its

operation mode.

• EPx_IMS – Endpoint interrupt mask (i.e. how endpoint responds

to generated interrupts).

• EPx_BUF – Hold buffer pointers for each endpoint. Two for

each endpoint (BUF0, BUF1).

Register Breakdown

CSR (core)

EP0_CSR

Bit 7 6 5 4 3 2 1 0 Description RESERVED UTMI STS SPD SUS Value RO RO RO RO RO RO RO RO

Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16

Description BSEL UC_DPD EP_TYPE TR_TYPE EP_DIS EP_NO LG SM

Value 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 1

Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Description DMA RO OTS TR_FR MAX_PL_SZ

Value 0 0 0 0 1 0 1 1 1 1 1 0 1 0 0 0

Status0: Unattached1: Attached

Speed0: Full1: High

Endpoint Type00: Control01: IN10: OUT11: RSVD

Transfer Type00: Interrupt01: Isochronous10: Bulk11: RSVD

Register Initialization

• USB Function Controller is memory mapped to address 0xCC000000.

• Assignments to / from offsets of this address will access the function controller registers.

• Write: – Register Read

– Bit AND / OR

– Register Write

RE

AD

RE

AD

/

W

RIT

E

USB Declaration & Registration

• Device Driver must declare itself with OS (Linux) USB core.

• Struct USB_Driver serves this purpose, by providing basic function information.

• Additional functionality supported via Struct File_Operations.

USB Driver Registration

Struct usb_device_id

Actual Registration

insmod usbf.ko

• Loading the driver on the lab FPGA…

Set EP0_CSR

Registration with usbcore

Probe() Function

• Called by Linux USB core when a device, matching the information provided in the id_table variable, is seen.– Check if driver will manage the specific device interface.

• Work typically done in this function:– Initializing local structures and buffers.– Detect endpoint addresses.– usb_set_intfdata(), usb_get_intfdata().

• Return 0 (Accept) or Negative (Reject).

Reference: linuxjournal.com

USB Driver Communication

• The driver is loaded and the device is initialized and registered with USB core. It’s time to use it!

• Two methods:– URBs (USB Request Block).– Non-URB alternatives.

What is an URB?

• Structures used by the driver to asynchronously send or receive data to or from a specific USB endpoint.– Similar to packets in networking.

• Formal methods and structures to creating, submitting, executing, and completing URBs.

• Notion of “Pipes”: Control, Bulk, Interrupt, and Isochronous.

Lifecycle of an URB

Reference: Free-Electrons.com

Alternatives to URBs

• Basic functions exist within USB core to allow data transfer without URBs.– usb_bulk_msg()– usb_control_msg()

• Caters to ease of use, however, affords less control over the transfer.– Requests cannot be cancelled.– Synchronously performed, put code to sleep.

Disconnect() Function

• Called by Linux USB core when a device, matching the information provided in the id_table variable, is removed.

• Work typically done in this function:– Clean up any private data during its operation.– Close out pending transfers or URBs.

Reference: linuxjournal.com

USB Deregistration

• Lastly, when the driver is unloaded or device is removed, the module deregisters.

Deregistration

THE END

Questions?

BACKUP

Original Intentions for Software

1. Develop low-level driver to initialize USB Function Controller registers.

2. Implement driver functions to allow very basic communication with a USB host.

Software Challenges

• New to Driver (and USB) development.– New concepts: Descriptors, URBs, Linux USB core and

handshaking.

• Understanding USB Function Controller.– Some function controllers can operate as a host

controller, which alters the driver’s role.

• Limited knowledge of USB Specification.

Assumptions

• USB Function Controller is used for a peripheral (slave) device.

• Controller uses only 3 of 16 available endpoints.– 0: Control– 1: IN– 2: OUT

USB Cable

• 4 Wires (Data+/-, Vbus, Gnd)

• Data Signals are Twisted Pair

Reference: www.usb.org