This talk will cover the USB fundamental needed to implement as USB HID joystick device using the Cypress PSoC 5 processor. The concepts covered by the talk are common to USB communications in general and can be used with other processors as well as implementing other types of devices.
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PSoC USB HID
1. Using the PSoC USB
March 17, 2012
Lloyd Moore, President/Owner
2. Overview
USB Background
USB Standard Classes
Endpoints and Transfer Types
Enumeration
USB Descriptors
Example Project
3. USB Background
Star topology, master / slave architecture
• Host is the master, initiates all communications
Multiple speeds: Low=1.5Mbps, Full=12
Mbps, High=480Mbps, Super=5Gbps
Self powered vs. Bus powered
• Low power: 100mA or 150mA Max (USB 2,3)
• High power: 500mA or 900mA Max (USB 2,3)
Vendor Id, Product Id, serial number
uniquely identify each device
4. Standard USB Classes
Audio Speakers, microphone,
Used to define the MIDI
USB device. Communication (CDC) Virtual Serial Port, modem,
Ethernet
Standardizes Content Security File and resource access
protocols and Firmware Upgrade (DFU) Device software upgrades
drivers for Human Interface (HID) Keyboards, mice, joysticks,
barcode scanners, UPS
common devices. IrDA Bridge IR communications
Allows operating Mass Storage Hard drives, DVD, flash
systems to Personal Healthcare
memory
Heart rate, blood pressure,
provide default glucose meters, ect.
drivers. Printer Printers – ya that simple!
Smart Card Phone cards, keyless entry
Can also create Still Image Capture Cameras, scanners
vendor specific Test & Measurement ADC, DAC, sensors, etc.
classes for custom Video Video cameras, web cams
applications.
5. Endpoints
Uniquely addressable portion of a USB device.
4 end points max for a low speed device, 16 for
other speeds
End point 0 is special, must be present and is
used for enumeration and control
Data transfer happens at end points.
Simplest way to think about an end point is that
it provides an addressable buffer to send and
receive data.
IN refers to dataflow TO the Host
OUT refers to dataflow FROM the Host
6. Transfer Types
Type Guarantees Typical Use
Control Presence, Device id and
Error Free configuration
Bulk Error Free Printer, hard
drive
Interrupt Latency Keyboard,
Error Free mouse
Isochronous Delivery rate Streaming
audio & video
7. Enumeration
Process by which the host discovers what devices
are connected and the properties of those
devices.
Utilizes a series of resets and Control transfers to
end point 0.
Each device given a unique address between 1
and 127.
Power and bandwidth requirements are collected
and allocated.
• Device will not be “connected” if resources are not
available.
Communication details collected by way of
“descriptors”
8. Descriptors
Data structures which allow the host to
learn about a device and how to
communicate with it.
Essentially a language which defines the
protocol between the host and each
device.
Can be quite complex but standard
descriptors are well defined.
Standard device drivers can interpret
these for a wide range of devices.
9. Example Project
Configure a PSoC 5 to send data from the
CapSense buttons and slider to a PC in the
form of a joystick.
Will be using the CY8CKIT-001, and PSoC
Creator 1.0 for this demo.
• Upgraded LCD display Lumex LCM-S02004DSR
• If using PSoC Creator 2.0 will also need to add
24Mhz crystal to bottom of processor module
due to a tighter clock requirement.
Data will be shown on LCD as well as sent
to PC.
Will be using a “canned” set of code as the
configuration is pretty time consuming.
10. Hardware Configuration
DebugLcd used to control the LCD display
CapSense will run the CapSense buttons
and slider control for input
• Heavy filtering here as the demo board USB
spews lots of noise to CapSense when running.
USBFS – USB 2.0 Full Speed driver, will
configure this to be a Joystick HID device
to send information to the PC.
13. USB Initialization Code
USBFS_Start() configures the
hardware
Next we wait while the USB device
goes through enumeration
Finally prepare the first set of data to
be dropped to the host when
requested
14. Main Loop
General operational pattern is to wait for
Host to grab data currently at the end
point, then replace it.
USBFS_bGetEPAckState() waits for grab
USBFS_LoadInEP() loads next batch of
data to be grabbed by the host
15. Resources
Book: USB Complete, Fourth Edition
• Jan Axelson
• ISBN: 978-1-931448-08-6
PSoC Application notes: AN57294, AN57473, AN58726
PSoC Product Web Site:
• http://www.cypress.com/?id=1353
PSoC Developer Community:
• http://www.psocdeveloper.com/forums/
PSoC Training On Demand:
• http://www.cypress.com/training
PSoC Full Development Kit (1, 3, 5): $249
• http://www.cypress.com/?rID=37464
My Contact Info:
• Lloyd@CyberData-Robotics.com
• http://www.CyberData-Robotics.com
16. Questions????
Will be around a bit after the
meeting for individual questions
Feel free to e-mail me
