Course: PIC18 USB Programming

Duration: 3 Days

Course Background

USB is the successor to RS232 for connecting devices to computers. PIC18 microcontrollers with on chip USB transceivers are now readily available. These devices are used in the implementation of sensors, data acquisition systems and control systems that can be connected to the PC and can also be used to implement simple mass storage devices. USB bootloaders can also be implemented for such devices.

Course Prerequisites and Target Audience

A good knowledge of embedded systems C programming is assumed. Detailed knowledge of USB is not required as USB standards and protocols will be covered in depth during the course.

Course Overview

The course introduces USB 1.x and 2.0 in depth and covers the theory and evolution of the USB standard up to USB 3.0. This is followed by coverage of the USB hardware on Microchip USB PIC18 microcontrollers and the associated firmware. There then follows an exploration of a USB devices classes and their uses - HID, CDC, MSD. As well as covering device side programming PC side application development for Microsoft Windows and/or Linux is covered. PC side application examples include both command line driven and GUI based (Graphical User Interface) applications. GUI programming examples will be presented as demonstrations with structured walkthroughs of the code. The course can be extended and tailored to go into PC side programming in greater depth if so required. Furthermore the host aspects of the course come in Microsoft Windows or Linux versions. If necessary the course can be tailored for a MAC OSX version.

Course Benefits

Students successfully completing this course will have a sound understanding of USB C programming. You will understand the development of USB applications using the HID (Human Interaction Device) and CDC (Communication Device Class) USB classes as well as how to work with USB MSD (Mass Storage Device) classes and the implementation of basic SD/MMC card based applications.

Course Outline

USB an Overview

Uses and limitations of USB
USB - Design considerations
Evolution of USB - from 1.0 to 1.1 to 2.0 to 3.0
USB On The Go (OTG)
Wireless USB
USB as a replacement for RS232

USB as a Networking Protocol

Layering and Network Protocols
ISO-OSI 7 layer model as it applies to USB
USB Network Topology - Logical vs. Physical
Host Responsibilities vs. Device Responsibilities
Network requirements depend on application requirements
Bus speed vs. Data throughput
How USB can support different kinds of traffic
USB 3.0 and its applicability to embedded systems

USB Device Hardware in PIC18 Microcontrollers

USB Device Architecture
Transceivers, Buffers and Interrupts
Ping Pong Buffering
DMA Support
Interrupts
Clocking and timing issues

Microchip MLA USB Firmware and USB Development Tools

Introduction the Microchip MLA USB Stack
Understanding Windows device drivers and INF driver installation files
Overview of (Dynamic Link Libraries) DLLs in Microsoft Windows
Overview of libusb and winusb and their use with applications involving PIC18 USB Devices

USB Transfers

Essential Concepts and Terminology
Endpoint - Source and Sink of data
Pipes - Stream pipes and Message pipes
Transfers and Transactions
Transfer types - uses and characteristics
Control transfers
Bulk transfers
Interrupt transfers
Isochronous transfers

Host - Device Interactions -- Rules of the Game

How a host learns about devices and recognises device attach and device detach events
Attachment and Detachment life cycle
Enumeration and device descriptors
Device removal issues
Device descriptor concepts and terminology
Device descriptor attributes
Control transfers - stages, states and elements
Standard control transfer requests

Device Classes

Class specifications
Overview of commonly defined classes

Human Interface
Mass storage
Communications
Smart card
Audio
Still image capture
Video
Personal Health Care

Host - Device Communications with host running under Microsoft Windows or Linux

Operating system concepts
User space vs. kernel space code
Operating system APIs
Device drivers and device driver programming
Operating system USB Driver Framework
User space USB driver programming
Working with libusb

Human Interface Devices - Theory and Practice

HID hardware and firmware requirements
HID Descriptor - Class descriptor, Report descriptors
Handling HID specific requests

Get Report
Set Report
Get Idle
Set Idle
Get Protocol
Set Protocol

Representing a Report Structure in C

HID USB Host Programming

Operating system aspects of the HID architecture
HID User Space Programming

HID USB Examples and Case Studies

HID keyboard using a keypad
HID Mouse using a potentiometer and some buttons
HID based sensors
HID based data acquisition and control applications

HID USB Examples and Case Studies

HID keyboard using a keypad
HID Mouse using a potentiometer and some buttons
HID based sensors
HID based data acquisition and control applications

CDC Class Devices

Overview of the CDC class and its uses
Operating system specific aspects concerning recognition of CDC class devices as serial ports
Data acquistion and control applications based on CDC

USB Mass Storage Class

Introduction to File Systems and their Architectures
FAT16 and FAT32 File Systems
Overview of the SCSI protocol and SCSI commands
Use of SCSI commands in Mass Storage Systems
Introduction to SD/MMC cards
Overview of the implementation of SD/MMC card drivers
Serial Data Logging Applications Using Mass Storage Device Technology