CE203303 PSoC 3 and PSoC 5LP Breathing LED.pdf

CE203303 - PSoC® 3 and PSoC 5LP Breathing LED
Objective
®
This example demonstrates the flexibility of a PSoC 3 or PSoC 5LP, by implementing a breathing LED effect exclusively in
hardware, with no CPU usage beyond initialization.
Overview
This example uses two PWMs and an XOR gate to make an LED gradually cycle through increasing and decreasing
brightness. There is no CPU usage beyond PWM initialization.
Requirements
Tool: PSoC Creator 3.2 or higher
Programming Language: C (GCC 4.8.4)
Associated Parts: All PSoC 3 and PSoC 5LP parts
Related Hardware: CY8CKIT-059, CY8CKIT-030, CY8CKIT-050, CY8CKIT-001
Design
The hardware design features two PWM Components, as Figure 1 shows. They have slightly different periods, with 50% duty
cycles. Routing them through an exclusive-OR (XOR) gate yields an output signal with a gradually changing duty cycle.
Driving an LED with this signal results in a “breathing” effect, where the LED gradually gets brighter and dimmer. The rate of
change is proportional to the difference between the PWM output frequencies.
Figure 1. Breathing LED Schematic (Pin and LED are selected for CY8CKIT-059)
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PSoC® 3 and PSoC 5LP Breathing LED
Design Considerations
This design can be extended in a number of ways:



Change the PWMs from 8-bit to 16-bit to get more precise control of the breathing rate.

Add an analog-to-digital converter (ADC), with a kit potentiometer as an analog input. Then use CPU firmware to change
the period of one of the PWMs based on the potentiometer position. This allows potentiometer-based control of the
breathing rate.
Use fixed-block PWMs (FF-TCPWM) instead of UDB-based PWMs to save UDB resources for other functions.
Connect a kit button through an input pin to the PWMs’ enable terminals. This allows hardware control of whether or not
the LED breathes, with no CPU usage.
This code example is designed for the PSoC 5LP device family and associated CY8CKIT-059 kit. The design is easily portable
to other PSoC 3, PSoC 4 and PSoC 5LP devices and kits, typically by just changing the LED, button, or potentiometer pin
assignments.
PSoC Creator Components
Table 1 lists the PSoC Creator Components used in this
example, as well as the hardware resources used by
each.
Table 1. List of PSoC Creator Components
Component
Hardware Resources
PWM_1
1 TCPWM, or ~1 UDB
PWM_2
1 TCPWM, or ~1 UDB
XOR gate
1 UDB macrocell
Clock_1
1 clock divider
Pin_LED
1 pin
Parameter Settings
Figure 2 shows the changed settings for the PWM Components.
Figure 2. PWMs Configuration
Operation
Plug the CY8CKIT-059 board into your computer’s USB port. Program the project into the kit, and observe the breathing effect
on the kit’s blue LED.
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Document No. 002-03303 Rev. **
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PSoC® 3 and PSoC 5LP Breathing LED
Related Documents
Table 2 lists all relevant application notes, code examples, knowledge base articles, device datasheets, and PSoC Creator
Component datasheets.
Table 2. Related Documents
Application Notes
AN54181, AN77759
Getting Started with PSoC 3
Getting Started with PSoC 5LP
Describes the PSoC 3 and PSoC 5LP, and how to build this code example.
PSoC Creator Component Datasheets
PWM
Supports fixed block and UDB-based PWMs
Digital Logic Gates
Supports creation of UDB-based logic gates to perform Boolean operations
Pins
Supports connection of hardware resources to physical pins
Device Documentation
PSoC 3 Datasheets
PSoC 3 Technical Reference Manuals
PSoC 5LP Datasheets
PSoC 5LP Technical Reference Manuals
Development Kit (DVK) Documentation
PSoC 3 and PSoC 5LP Kits
PSoC Resources
If you are new to PSoC, Cypress provides a wealth of data at www.cypress.com to help you to select the right PSoC device for
your design, and quickly and effectively integrate the device into your design. For a comprehensive list of resources, see
knowledge base article KBA86521, How to Design with PSoC 3, PSoC 4, and PSoC 5LP. The following is an abbreviated list
for PSoC 3 and PSoC 5LP:





Overview: PSoC Portfolio, PSoC Roadmap
Product Selectors: PSoC 1, PSoC 3, PSoC 4, or
PSoC 5LP. In addition, PSoC Creator includes a
device selection tool.
Datasheets: Describe and provide electrical
specifications for the PSoC 3 and PSoC 5LP device
families
Technical Reference Manuals (TRM): Provide
detailed descriptions of the architecture and registers
in the PSoC 3 and PSoC 5LP device families.
Application Notes and Code Examples: Cover a
broad range of topics, from basic to advanced level.
Many of the application notes include code examples.
PSoC Creator provides additional code examples.
Recommended application notes for getting started
with PSoC 3 and PSoC 5LP are:
 AN54181, Getting Started with PSoC 3
 AN77759, Getting Started with PSoC 5LP
 AN61290, Hardware Design Considerations
 AN57821, Mixed Signal Circuit Board Layout
 AN81623, Digital Design Best Practices
 AN73854, Introduction To Bootloaders
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
PSoC Training Videos: These videos provide step-bystep instructions on how to get started building
complex designs with PSoC.
 Development Kits:
• CY8CKIT-059 is a low-cost platform for prototyping
products with PSoC 5LP. It has a unique snap-away
programmer and debugger on the USB connector:
• CY8CKIT-030 and CY8CKIT-050 are designed for
analog performance. They enable you to evaluate,
develop and prototype high precision analog, lowpower and low-voltage applications powered by
PSoC 3 or PSoC 5LP.
• CY8CKIT-001 provides a common development
platform for any one of the PSoC 1, PSoC 3, PSoC 4,
or PSoC 5LP families of devices.
The MiniProg3 device provides an interface for flash
programming and debug.
Document No. 002-03303 Rev. **
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PSoC® 3 and PSoC 5LP Breathing LED
PSoC Creator
PSoC Creator is a free Windows-based Integrated Design Environment (IDE). It enables concurrent hardware and firmware
design of systems based on PSoC 3, PSoC 4, and PSoC 5LP. See Figure 3 – with PSoC Creator, you can:
1.
2.
Drag and drop Components to build your hardware
system design in the main design workspace
3.
Configure Components using configuration tools
4.
Explore the library of 100+ Components
Codesign your application firmware with the PSoC
hardware
5.
Review Component datasheets
Figure 3. PSoC Creator Features
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Document No. 002-03303 Rev. **
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PSoC® 3 and PSoC 5LP Breathing LED
Document History
®
Document Title: PSoC 3 and PSoC 5LP Breathing LED - CE203303
Document Number: 002-03303
Revision
ECN
**
4940060
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Orig. of
Change
MKEA
Submission
Date
10/08/2015
Description of Change
New code example
Document No. 002-03303 Rev. **
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PSoC® 3 and PSoC 5LP Breathing LED
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