Application Note
AN_191
Vinculum-II Interrupts
Version 1.0
Issue Date: 2012-06-22
This application note introduces interrupts, and how they are implemented in
the FTDI Vinculum-II device. A hardware example is provided.
Use of FTDI devices in life support and/or safety applications is entirely at the user’s risk, and the
user agrees to defend, indemnify and hold FTDI harmless from any and all damages, claims, suits
or expense resulting from such use.
Future Technology Devices International Limited (FTDI)
Unit 1, 2 Seaward Place, Glasgow G41 1HH, United Kingdom
Tel.: +44 (0) 141 429 2777 Fax: + 44 (0) 141 429 2758
Web Site: http://ftdichip.com
Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
Table of Contents
1
2
Introduction .................................................................................................................................... 2
1.1
Hardware used to demonstrate GPIO interrupt ..................................................................... 2
1.2
Available VNC2 Interrupts....................................................................................................... 3
1.3
Levels and Edges ..................................................................................................................... 3
Firmware Details ............................................................................................................................. 4
2.1
Configure IOMux ..................................................................................................................... 5
2.2
Configure GPIO Interrupts ...................................................................................................... 6
2.3
Wait for Interrupt.................................................................................................................... 7
3
Using IDE to Monitor Thread States ............................................................................................... 8
4
Conclusion ....................................................................................................................................... 9
5
Contact Information...................................................................................................................... 10
Appendix A – References ...................................................................................................................... 11
Document References....................................................................................................................... 11
Acronyms and Abbreviations ............................................................................................................ 11
Appendix B – List of Tables & Figures ................................................................................................... 12
List of Tables ..................................................................................................................................... 12
List of Figures .................................................................................................................................... 12
Appendix C – Revision History .............................................................................................................. 13
1
Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
1 Introduction
This document explains what interrupts are, why they are useful for embedded programmers, and
how they are implemented in Vinculum-II (VNC2) firmware. A sample hardware application is used
to demonstrate how interrupts are used in a real world example. The FTDI Vinco board and a 3rd
party LCD shield will be used in the example.
The reader should be familiar with the VNC2 IDE and Vinco development board. It is also assumed
that the reader has an understanding of the Vinculum Operating System (VOS).
Interrupts are used in embedded systems to signal the processor that an external event has taken
place. Examples could include the arrival of data on a bus, flipping a switch or if a specific amount
of time has passed.
Interrupts allow designers to isolate time critical operations from the main program to guarantee
they are processed in a timely manner.
Since interrupts are asynchronous, they can occur at any time when the main program is running.
An interrupt mask is used to select the desired type of interrupt.
After reading this app note, the reader will be able to understand and write interrupt based code
for the Vinculum II.
1.1 Hardware used to demonstrate GPIO interrupt
Vinco development board
LCD Shield for Arduino/Vinco
VNC2 Debugger module
External pushbutton
Appendix A has the datasheet links for the above hardware.
Figure 1.1 LCD Shield for Vinco
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
1.2 Available VNC2 Interrupts
The following VNC2 ports and interfaces have interrupt support:
USB Port
GPIO Port
SPI Port
USB Host 0
GPIO Port A
SPI Master
USB Host 1
GPIO Port B
SPI Slave 1
USB Slave 1
PWM
Interface
FIFO Port
PWM
FIFO
SPI Slave 2
USB Slave 2
Table 1.1 Available VNC2 Interrupts
An interrupt mask is used to select one of the above interrupts. In this application note, GPIO Port
pin B_0 (Pin 51) will be used as an interrupt. Multiple interrupts such as PWM and GPIO are
allowed since they are different functions.
For GPIO interrupts, Port B supports interrupts from a specified pin. Port A will trigger an interrupt
if any of the Port A pins toggle.
1.3 Levels and Edges
Level sensitive interrupts force the VNC2 to respond as long as the interrupt signal is at a specified
level. Edge sensitive interrupts force the VNC2 to respond when the interrupt signal makes a
transition. Levels can be logic low or logic high, edges can be rising or falling. Figure 1.2 shows a
positive level sensitive interrupt and a falling edge sensitive interrupt.
Figure 1.2 Interrupt Types
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
2 Firmware Details
In this section, the function calls used to configure an interrupt and send the result to a LCD
display will be discussed. The source code can be downloaded from the following link
http://www.ftdichip.com/Support/SoftwareExamples/VinculumIIProjects/AN_191_Source_Code.zip
Figure 2.1 shows the basic operation of the interrupt application code.
Figure 2.1 Interrupt Application Flowchart
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
2.1 Configure IOMux
The Vinco module needs to have its GPIO signals configured to interface with the LCD shield. A
16x2 monochrome LCD is used. The LCD control code is explained in more detail in Application
Note AN_153, Vinco LCD Interface Example.
Pin 51 is the interrupt input. To sensitize this input for a falling edge interrupt, it has been
configured as:
Schmitt Trigger
Fast slew rate
75K Pull Up
if (vos_get_package_type() == VINCULUM_II_64_PIN)
{
// GPIO_Port_A_0 to pin 57 as Output.
vos_iomux_define_output(57, IOMUX_OUT_GPIO_PORT_A_0); //LCD DB4 input
// GPIO_Port_A_1 to pin 58 as Output.
vos_iomux_define_output(58, IOMUX_OUT_GPIO_PORT_A_1); //LCD DB5 input
// GPIO_Port_A_2 to pin 59 as Output.
vos_iomux_define_output(59, IOMUX_OUT_GPIO_PORT_A_2); //LCD DB6 input
// GPIO_Port_A_3 to pin 60 as Output.
vos_iomux_define_output(60, IOMUX_OUT_GPIO_PORT_A_3); //LCD DB7 input
// GPIO_Port_A_6 to pin 17 as Output.
vos_iomux_define_output(17, IOMUX_OUT_GPIO_PORT_A_6); //LCD RS input
// GPIO_Port_A_7 to pin 18 as Output.
vos_iomux_define_output(18, IOMUX_OUT_GPIO_PORT_A_7); //LCD EN input
// GPIO_Port_C_3 to pin 23 as Output. //Port C is used to isolate this signal
vos_iomux_define_output(23, IOMUX_OUT_GPIO_PORT_C_3); //Backlight for LCD
// GPIO_Port_B_0 to pin 51 as Input. // Configure for Port B_0 Interrupt
vos_iomux_define_input(51, IOMUX_IN_GPIO_PORT_B_0);
vos_iocell_set_config(51,
VOS_IOCELL_DRIVE_CURRENT_4MA,
VOS _IOCELL_TRIGGER_SCHMITT,
VOS_IOCELL_SLEW_RATE_FAST,
VOS_IOCELL_PULL_UP_75K);
}
5
Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
2.2 Configure GPIO Interrupts
To set up a GPIO interrupt, the following steps must take place:
Set interrupt mask for interrupts on GPIO B
Specify which pin on port B to monitor
Specify if interrupt is level sensitive or edge sensitive
Specify the polarity of the interrupt (high/low level, rising/falling edge)
Enable/Disable the interrupt
//Open GPIO Port B
hGpioB = vos_dev_open(GPIOB);
// Setup Interrupt Mask for GPIO B
gpio_iocb.ioctl_code = VOS_IOCTL_GPIO_SET_MASK;
gpio_iocb.value = 0x00 ; //set all as input
vos_dev_ioctl(hGpioB, &gpio_iocb);
// Setup Interrupt for INT_0 on port B_0
gpio_iocb.ioctl_code = VOS_IOCTL_GPIO_SET_PROG_INT0_PIN;
gpio_iocb.value = GPIO_PIN_0; // Port B_0
vos_dev_ioctl(hGpioB, &gpio_iocb);
// Setup for Interrupt on falling edge transition
gpio_iocb.ioctl_code = VOS_IOCTL_GPIO_SET_PROG_INT0_MODE;
gpio_iocb.value = GPIO_INT_ON_NEG_EDGE;
vos_dev_ioctl(hGpioB, &gpio_iocb);
// Enable interrupt
vos_enable_interrupts(VOS_GPIO_INT_IEN);
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
2.3 Wait for Interrupt
The GPIO_B0 interrupt works by monitoring the state of this input. A “Waiting on Interrupt”
message is sent to the LCD before configuring the interrupt.
Before the interrupt triggers, the VOS_IOCTL_WAIT_ON_INT0 call blocks a 2nd write to the LCD
display. A pushbutton is connected between port B0 and a ground pin, as illustrated in Figure 1.1
When B0 makes a high to low transition (pushbutton is pressed), the rest of the thread is
unblocked and is allowed to execute.
To simplify the design of the interrupt, the state of port B is read by VOS_DEV_READ when the
interrupt triggers. The default state of port has been set to 0xFF. When a B0 goes low, port B is
no longer 0xFF, and an “Interrupt Triggered” message is sent to the LCD display.
Pre-interrupt string to display:
unsigned char *lcd_str ;
unsigned char *lcd_str1, *lcd_str2;
lcd_str1 = "Waiting.....";
lcd_str2 = "For Interrupt";
Wait for interrupt code:
gpio_iocb.ioctl_code = VOS_IOCTL_GPIO_WAIT_ON_INT0;
vos_dev_ioctl(hGpioB, &gpio_iocb);
//Code is blocked from executing until interrupt occurs
//Read the state of Port B (preset to 0xFF)
vos_dev_read(hGpioB, &B0,1,&num_read);
// If Port B is not 0xFF, we have confirmed the interrupt
// Write message to LCD indicating interrupt was triggered
if (B0 != 0xFF)
{
lcd_str1 = "Interrupt B0 Has";
lcd_str2 = "Been Triggered";
}
}
} while (1);
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
3 Using IDE to Monitor Thread States
The firmware thread in the code has been labeled as “Interrupt Thread” by the
vos_create_thread_ex call.
// create thread for firmware application (no parameters)
tcbFirmware = vos_create_thread_ex(29, SIZEOF_THREAD_MEMORY, firmware, "Interrupt
Thread", 0);
This allows the IDE’s Thread Manager to display the state of the interrupt thread before and after
execution. The IDE must be used in debug mode for the Thread Manager to work.
While waiting for interrupt on GPIO B0, thread is blocked:
Figure 3.1 Thread Manager Pre-Interrupt
After Interrupt has triggered on GPIO B0, thread is unblocked:
Figure 3.2 Thread Manager Post-Interrupt
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
4 Conclusion
This document has introduced basic GPIO interrupts with the Vinculum-II. Other Vinculum-II
interfaces can initiate interrupts, such as pulse width modulation (PWM) and Serial Peripheral
Interface (SPI).
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
5 Contact Information
Head Office – Glasgow, UK
Branch Office – Hillsboro, Oregon, USA
Future Technology Devices International Limited
Unit 1, 2 Seaward Place, Centurion Business Park
Glasgow G41 1HH
United Kingdom
Tel: +44 (0) 141 429 2777
Fax: +44 (0) 141 429 2758
Future Technology Devices International Limited
(USA)
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USA
Tel: +1 (503) 547 0988
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E-mail (Sales)
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Branch Office – Shanghai, China
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(Taiwan)
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Taiwan , R.O.C.
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http://ftdichip.com
System and equipment manufacturers and designers are responsible to ensure that their systems, and any Future Technology
Devices International Ltd (FTDI) devices incorporated in their systems, meet all applicable safety, regulatory and system-level
performance requirements. All application-related information in this document (including application descriptions, suggested
FTDI devices and other materials) is provided for reference only. While FTDI has taken care to assure it is accurate, this
information is subject to customer confirmation, and FTDI disclaims all liability for system designs and for any applications
assistance provided by FTDI. Use of FTDI devices in life support and/or safety applications is entirely at the user’s risk, and the
user agrees to defend, indemnify and hold harmless FTDI from any and all damages, claims, suits or expense resulting from
such use. This document is subject to change without notice. No freedom to use patents or other intellectual property rights is
implied by the publication of this document. Neither the whole nor any part of the information contained in, or the product
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of the copyright holder. Future Technology Devices International Ltd, Unit 1, 2 Seaward Place, Centurion Business Park,
Glasgow G41 1HH, United Kingdom. Scotland Registered Company Number: SC136640
10
Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
Appendix A – References
Document References
AN_142 Vinculum II Tool Chain Getting Started Guide
AN_153 Vinco LCD Interface Example
AN_151 Vinculum User Guide
Arduino LCD Keypad Shield Web Page
Arduino LCD Keypad Shield Technical Details
Vinco Datasheet
http://www.ftdichip.com/Support/SoftwareExamples/VinculumIIProjects/AN_191_Source_Code.zip
Acronyms and Abbreviations
Terms
LCD Shield
Interrupt
Description
An Arduino compatible plug in LCD display that is easily adapted for use
with the FTDI Vinco board.
A signal that indicates an external event has taken place.
Interrupt Mask
A command that selects which type of hardware interrupt to process.
Edge Sensitive
Interrupt
An interrupt event triggered by a falling or rising edge
Level Sensitive
Interrupt
An interrupt triggered by a high or low logic level.
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Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
Appendix B – List of Tables & Figures
List of Tables
Table 1.1 Available VNC2 Interrupts ...................................................................................... 3
List of Figures
Figure 1.1 LCD Shield for Vinco ............................................................................................ 2
Figure 1.2 Interrupt Types .................................................................................................. 3
Figure 2.1 Interrupt Application Flowchart ............................................................................. 4
Figure 3.1 Thread Manager Pre-Interrupt .............................................................................. 8
Figure 3.2 Thread Manager Post-Interrupt ............................................................................. 8
12
Copyright © 2012 Future Technology Devices International Limited
Application Note
AN_191 Vinculum-II Interrupts
Version 1.0
Document Reference No.: FT_000531 Clearance No.: FTDI# 299
Appendix C – Revision History
Document Title:
AN_191 Vinculum 2 Interrupts
Document Reference No.:
FT_000531
Clearance No.:
FTDI# 299
Product Page:
http://www.ftdichip.com/FTProducts.htm
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Revision
draft
1.0
Changes
Date
Initial draft subject to change
2012-05-16
First Release
2012-02-22
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