1. Embedding USB technology Limitations, challenges and compliance
USB Host
USB Compliance
November Christian Légaré

2. USB Device stack Application USB Class API Class Drivers
Kernel
USB Class API
Class Drivers
Kernel Abstraction
HID
Mass storage
CDC
Custom drivers
USB Device core stack
Device Controller Driver
Device Controller Hardware

3. USB Host stack Application USB Class API Class Drivers
Kernel
USB Class API
Class Drivers
Kernel Abstraction
HID
Mass storage
CDC
Hub
Custom drivers
USB Host core stack
Bandwidth allocation & Power management
Host Controller Driver
OHCI-EHCI-xHCI or Custom
Host Controller Hardware

4. Device Driver
Select device driver
The host loads the appropriate driver using a PID/VID (Product ID/Vendor ID) combination used during the enumeration.
[Windows] Abstract from a .inf file:
[DeviceList]
%USB\VID_8765&PID_1234.DeviceDesc%=USBBulkInstall, USB\VID_8765&PID_1234
The VID is supplied by the USB Implementor's forum at a cost and this is seen as another sticking point for USB. The latest info on fees can be found on the USB Implementor’s Website
Other standards organizations provide a extra VID for non-commercial activities such as teaching, research or fiddling (The Hobbyist). The USB Implementors forum has yet to provide this service. In these cases, the developper may wish to use one assigned to the development system's manufacturer. For example most chip manufacturers will have a VID/PID combination the developper can use for the chips which is known not to exist as a commercial device. Other chip manufacturers can even sell a PID to use with their VID for the commercial device. 4

5. General Purpose OS USB drivers
With a USB Device based product, using HID or MSD allows for the use of generic drivers in the General Purpose OS (Windows, Linux, Android, MacOS)..a definite advantage for product acceptance and deployment
Other classes may require custom drivers for these Operating Systems

6. USB On-The-Go Supplement to USB 2.0
Allows for devices to be host and peripheral
New features:
Smaller connectors with an added pin (ID)
Tighter power constraints for devices
Protocol enhancement for dynamic switching (HNP)
Definition of session request protocols (SRP)

7. USB On-The-Go Allows two USB devices to talk without a PC as host.
DRD (Dual Role Devices).
Unique mini-AB receptacle.
OTG High Speed and Full Speed.
Low power requirements on battery powered devices.

8. USB On-The-Go Application OTG stack Host stack Device stack
OTG Controller Driver
Host driver
Device driver
Host Controller Hardware
Device Controller Hardware

9. Wireless USB
Certified Wireless USB is the new wireless extension to USB that combines the speed and security of wired technology with the ease-of-use of wireless technology
Certified Wireless USB is the first high-speed wireless personal interconnect technology to meet the needs of multimedia consumer electronics, PC peripherals, and mobile devices.
Certified Wireless USB will preserve the functionality of wired USB while also unwiring the cable connection and providing enhanced support for streaming media CE devices and peripherals.
Certified Wireless USB performance is targeted at 480Mbps at 3 meters and 110Mbps at 10 meters.

10. Compliance Usage of the USB logo requires a product to be compliant
The USB organization has created a compliance program
Two main criteria are: checklists and compliance testing
Checklists contain questions relating to a product and its behavior
USB-IF provide a Compliance Program for a small membership fee
There are a set of registered USB logos which are not interchangeable

11. Tests Mechanical Electrical Interoperability Device Software
OK when using an approved connector vendor
Electrical
OK when using a silicon vendor reference design
Interoperability
The USB Gold Tree
Device Software
OK with Command Verifier
Host Software
Proprietary and expensive

12. USB Electrical Analysis Tool
USBET20 is a stand-alone electrical signal analysis tool for USB Compliance testing. USBET20 is the official compliance electrical analysis tool that performs pass/fail assessments on signal quality and inrush current data captured from an oscilloscope. USBET20 is downloadable from

13. USB Device and the USB Command Verifier
USB20CV is the compliance test tool which evaluates High, Full and Low-speed USB devices for conformance to the USB Device Framework (Chapter 9), Hub device class (Chapter 11), HID class, and OTG specifications. Also included are mass storage class, USB video class and PDHC specification tests.
All USB 2.0 and 3.0 peripherals are required to pass the Device Framework tests in order to gain certification.
USB20CV
USB30CV

14. If your product is a USB Host How do you test a Host?
There is only one Host on a bus and the Host is the Master on the bus.
So, how do you test a Host?
Protocol Analyzer and Generator (build test cases)
Custom tools

15. Interoperability : USB Gold Tree
A Host PC with different USB controllers
5 HS self powered hubs
1 FS self powered hub
EHCI
1 FS keyboard/hub
OHCI
5 5 meter USB cables
UHCI
1 mouse
xHCI (USB 3.0)
2 mass storage devices
1 video camera

16. Memory footprint Device-Bulk
Detail
Description
CPU
Philips LPC2148
Toolchain
IAR Embedded Workbench v4.30a
ARM/Thumb mode
Thumb mode
Compile options
Size optimization (Low)
Memory requirements
The following table shows the memory requirement of the project:
The USB receive buffer is listed separately because this buffer can be reduced to a trivial size if optimal performance is not required.
Detail
ROM
[bytes]
RAM
USB code and const data
6309 --
USB data 32
USB receive buffer
512
Total
544

17. Memory footprint Device-MSD
System
Detail
Description
CPU
Philips LPC2148
Toolchain
IAR Embedded Workbench v4.30a
ARM/Thumb mode
Thumb mode
Compile options
Size optimization (Low)
Memory requirements (RAMDisk)
ROM and RAM will vary depending on the storage device used.
RAM space beyond that which is reflected by the table will also be needed, of course, if RAM is chosen as the application's storage medium.
The sector buffer's size corresponds to the sector size utilized by the actual storage device, more than 512 bytes may be necessary.
Detail
ROM
[bytes]
RAM
USB code and const data
6736 --
USB data 32
USB receive buffer
512
MSD sector buffer
Total
1056
The USB receive buffer is listed separately because this buffer can be reduced to a trivial size if optimal performance is not required. 17

18. Memory footprint Host-HID
System
The following table shows the hardware and the toolchain details of the project:
Detail
Description
CPU
ARM9
Toolchain
IAR Embedded Workbench v4.30a
ARM/Thumb mode
ARM mode
Compile options
None
Memory requirements
The following table shows the memory requirement of the project:
64k of the RAM data is a memory pool in the usbh_lib module. Depending on your application it may not be required.
Detail
ROM
[bytes]
RAM
Host driver
11572
440
HID Class driver
6864 36
Mouse and keyboard demo code
2392
8036
USB core
18837
66121
Total
39665
74633 18

19. Memory footprint Host-MSD
System
The following table shows the hardware and the toolchain details of the project:
Detail
Description
CPU
ARM9
Toolchain
IAR Embedded Workbench v4.30a
ARM/Thumb mode
ARM mode
Compile options
None
Memory requirements
The following table shows the memory requirement of the project:
Detail
ROM
[bytes]
RAM
Host driver
11572
440
MSD Class driver
7842
548
Mouse and keyboard demo code
2392
8036
USB core
18837
2121
Total
40643
11145 19

20. Final review
Embedding USB

21. USB features or limitations
USB works great for well defined classes
Typical usage like HID or MSC
If you want to leverage the technology, then think about:
Maximum data rates
Actual data throughput
Cable length and total length
Power
127 devices per controller
Host driven protocol

22. Have Reasonable Expectations
Typical MCU can not keep up with High speed USB controllers.
USB device controllers are sometimes troublesome to port.
This is partly because a USB device controller port deals more closely with more complicated hardware than, say, a TCP/IP NIC port.  Partly, this is because USB device controllers are much more various than NICs.
The Device can never initiate a communication with USB 2.0.
If using MSD (Host or Device) & a file system on the embedded system, either the MSD or the file system (but not both) can access the storage media at any time.

23. Embedding USB
Average microcontroller clock is between 100Mhz and 200Mhz. USB 2.0 High Speed can deliver 480 Mbps…not on a microcontroller!
Semiconductor vendors advertise their parts as being USB 2.0 compliant!
Not all USB controllers are created equal
For Host, many don’t follow the OHCI, EHCI or UHCI specs.
Some hardware functions moved to software reducing even more the expected performance
Number of endpoints may be lower than the specification, limiting the product capabilities

24. USB markets The USB key has changed the rule Consumer Medical
USB Host stack integrated to take advantage of USB MSD and the Flash drives.
Consumer
Mouse, Keyboard, Printers, Digital cameras, etc…
Medical
New market for Personal Medical Devices
USB Decorations

25. Summary Appealing features:
Ease of use
Bus power
Auto-detection and self configuration
Expandability
Reasonable speed
Large number of predefined functions and customizable function
Availability of peripherals
Flexibility and reliability
The tradeoff is complex implementation and cost 25

26. Thank you 26