Introduction to USB Agenda Introduction to USB LPC23xx Block - - PowerPoint PPT Presentation

Introduction to USB

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Agenda

Introduction to USB LPC23xx Block diagram MCB2300 demo

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Introduction to USB

Plugging the USB cable

Communication flow Lets talk about USB applications

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USB- A Brief History

USB 1.1 USB 2.0 OTG

Approved on 11/23/99 by the USB Core team 12 Mbps bus Full-speed (12 Mbps) Low-speed (1.5 Mbps) Standard A connector and standard B connector Interrupt (OUT) Transfer was added Original USB 2.0 specification released

• n April 27, 2000

480 Mbps bus High-speed (480 Mbps) Full-speed (12 Mbps) Low-speed (1.5 Mbps) Backward compatible with USB 1.1 New mini-B connector Supplements the 2.0 specification Connects peripherals directly to each

• ther (peer to peer)

New mini-A connector and mini- AB receptacle

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Plugging the USB Cable

Bus enumeration

– The process of identifying and configuring USB devices

During enumeration:

– Assigning an address – Reading “Descriptors” from device – Assigning and loading a device driver

Host software responsibility

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Descriptors

Data Structure with a defined format that enables a host to learn about a device and its capabilities. Device Descriptor Configuration Descriptor Interface Descriptor Interface Descriptor

Endpoint Descriptor Endpoint Descriptor Endpoint Descriptor Endpoint Descriptor

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Introduction to USB

Plugging the USB cable

Communication flow

Lets talk about USB applications

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IN and OUT Transactions

Data flows IN and OUT with respect to the host “IN Transaction” “OUT Transaction”

IN OUT HOST

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Endpoint Explained

An endpoint is a buffer used to transmit or receive data Each endpoint has a direction and an address Up to 32 (16 pairs) endpoints can reside within a device Although a host has buffers, it does not have endpoints

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Introduction to USB

Plugging the USB cable Communication flow

Lets talk about USB applications

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USB Applications

Control Transfer (Bus Enumeration) Interrupt Transfer Bulk Transfer Isochronous Transfer

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Interrupt Transfer (1)

Device never interrupts the host. Host polls the device Only way low speed devices can transfer data Also used by the host to send data to the device on a scheduled basis Maximum packet size: 1-64

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Interrupt Transfer (2)

DATA STAGE

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Bulk Transfer (1)

Used for large amount of data Only full and high-speed devices Host controller ensures that bulk transfer are eventually completed but it does not guarantee bandwidth Fastest transfer type on an otherwise idle bus Maximum packet size: 8,16,32,64,512

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Bulk Transfer (2)

DATA STAGE

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Isochronous Transfer (1)

Fixed number of bytes per frame. Bandwidth is guaranteed No error correction – No ACK field Used for continuous communication of time- relevant information (streaming data) Full and high-speed devices only Maximum Packet size: 1-1023

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Isochronous Transfer (2)

DATA STAGE No ACK field

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Control Transfer (1)

Enables the host to read information about the device (enumeration) All devices must support Control Transfers at Endpoint 0 Control transfers require both an IN and OUT Endpoint Talks to the device through Address 0 while enumeration Maximum Packet Size: 8,16,32,64

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Control Transfer (2)

SETUP STAGE DATA STAGE STATUS STAGE

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USB Communication Blocks (1)

Transfer

Transfer Types

• Control
• Interrupt
• Bulk
• Isochronous

Handshake Packet Data Packet Token Packet

Transaction Types

• OUT
• IN
• SOF (Start of Frame)
• SETUP

Transaction Transaction

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USB Communication Blocks (2)

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LPC23xx

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LPC2300 Family

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LPC2378 (1)

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LPC2378 (2)

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Dual AHB

Concurrent operations become possible:

– Ethernet packet reception and transfer to SRAM – CPU Instruction Fetch – USB packet reception and transfer to SRAM – GP DMA

Dedicating AHB Bus to Ethernet is required to guarantee 100 Mbits/sec Ethernet throughput without contention with other peripherals

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USB 2.0

Fully Compliant with USB 2.0 Spec Supports Control, Bulk, Interrupt and Isochronous endpoints Scalable realization of Endpoints at Run time Double buffering supported for Bulk and Isochronous Endpoints Supports DMA transfer on all non-control endpoints

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Available USB Device Stacks for LPC2300/2400/214x

(list does not claim to be complete…) Keil RL-USB:

– http://www.keil.com/arm/rl-arm/rl-usb.asp

Micrium µC/USB Device

– http://www.micrium.com/products/usb/usb-device/overview.html

Micro Digital smxUSBD

– http://www.smxrtos.com/rtos/usb/smxusbd.htm

HCC Embedded USB (EUSB) Device Stack

– http://www.hcc-embedded.com/site.php?mid=120

CMX-USB

– http://www.cmx.com/cmx_usb.pdf

Express Logic USBX

– http://www.rtos.com/page/product.php?id=6

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Available USB Host Stacks for LPC2400/ LPC3180

(list does not claim to be complete…)

Micrium µC/USB Host

– http://www.micrium.com/products/usb/usb-host/usb-host.html

Micro Digital smxUSBH

– http://www.smxrtos.com/rtos/usb/smxusbh.htm

HCC Embedded USB (EUSB) HostLite Stack

– http://www.hcc-embedded.com/site.php?mid=180

Express Logic USBX

– http://www.rtos.com/

OnChip Technology

– http://www.onchiptech.com/wb/pages/products/otusb.php

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