Using the PSoC USB
March 17, 2012
Lloyd Moore, President/Owner
Overview
USB Background
 USB Standard Classes
 Endpoints and Transfer Types
 Enumeration
 USB Descriptors
 Example Project
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USB Background
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Star topology, master / slave architecture
• Host is the master, initiates all
communications
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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)
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Vendor Id, Product Id, serial number
uniquely identify each device
Standard USB Classes
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Used to define the
USB device.
Standardizes
protocols and
drivers for
common devices.
Allows operating
systems to
provide default
drivers.
Can also create
vendor specific
classes for custom
applications.
Audio
Speakers, microphone,
MIDI
Communication (CDC)
Virtual Serial Port, modem,
Ethernet
Content Security
File and resource access
Firmware Upgrade (DFU)
Device software upgrades
Human Interface (HID)
Keyboards, mice, joysticks,
barcode scanners, UPS
IrDA Bridge
IR communications
Mass Storage
Hard drives, DVD, flash
memory
Personal Healthcare
Heart rate, blood pressure,
glucose meters, ect.
Printer
Printers – ya that simple!
Smart Card
Phone cards, keyless entry
Still Image Capture
Cameras, scanners
Test & Measurement
ADC, DAC, sensors, etc.
Video
Video cameras, web cams
Endpoints
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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
Transfer Types
Type
Guarantees
Typical Use
Control
Presence,
Error Free
Error Free
Device id and
configuration
Bulk
Interrupt
Isochronous
Latency
Error Free
Delivery rate
Printer, hard
drive
Keyboard,
mouse
Streaming
audio & video
Enumeration
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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.
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Communication details collected by way of
“descriptors”
Descriptors
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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.
Example Project
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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.
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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.
Hardware Configuration
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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.
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USBFS – USB 2.0 Full Speed driver, will
configure this to be a Joystick HID device
to send information to the PC.
Device Descriptor
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Walkthrough live configuration of
descriptor.
Clock Configuration
IMO = 24.000 MHz
USB = IMOx2
ILO = 100KHz
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
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Main Loop
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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
Resources
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Book: USB Complete, Fourth Edition
• Jan Axelson
• ISBN: 978-1-931448-08-6
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PSoC Application notes: AN57294, AN57473, AN58726
PSoC Product Web Site:
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http://www.cypress.com/?id=1353
PSoC Developer Community:
• http://www.psocdeveloper.com/forums/
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PSoC Training On Demand:
• http://www.cypress.com/training
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PSoC Full Development Kit (1, 3, 5): $249
• http://www.cypress.com/?rID=37464
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My Contact Info:
• Lloyd@CyberData-Robotics.com
• http://www.CyberData-Robotics.com
Questions????
Will be around a bit after the
meeting for individual questions
 Feel free to e-mail me
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