|
The Capture Compare (CCP) peripheral of the PIC16 and PIC18 PIC® MCUs and the Input Capture (IC) peripheral of the dsPIC and PIC24 PIC® MCUs allow the MCU to capture and hold a timer value when a specific input pin reaches a user defined state. This peripheral is useful for measuring the duration between events, or determining the frequency or duty cycle of an incoming signal. This peripheral operates independent of the MCU operation, meaning it can trap the timer on the input signal without the developer having to block code execution waiting for the input signal to happen.
Version 5 of the CCS C Compiler has added a #use capture() library that makes it easy to use the CCP or IC peripheral. The API for this library provides an easy to use method for using and configuring the peripheral and timers, while also being portable from one PIC® MCU device to another. Here is an example of its use:
#use capture(CCP1, input=PIN_C2, capture_rising, stream=CAPTURE1)
unsigned int16 WaitForEvent(void)
{
while(!get_capture_event(CAPTURE1));
return(get_capture_time(CAPTURE1)); }
#use capture() configures a CCP or IC peripheral for use, and by using the STREAM option several peripherals can be configured with several instances of #use capture(). #use capture() also provides a method of configuring the timer peripheral to use and the tick rate of the timer. Several other configuration options exist, see the compiler help manual for documentation.
get_capture_event() returns TRUE if the CCP or IC peripheral has trapped an event that can be read, and get_capture_time() returns the time the event happened.
The CCS C Compiler provides an example of using this library, ex_use_caputure.c which can be found in the examples directory of the CCS C Compiler. This example can be used on any PCM, PCH or PCD version 5 CCS C Compiler.
Like us on Facebook. Follow us on Twitter.
About CCS:
CCS is a leading worldwide supplier of embedded software development tools that enable companies to develop premium products based on Microchip PIC® MCU and dsPIC® DSC devices. Complete proven tool chains from CCS include a code optimizing C compiler, application specific hardware platforms and software development kits. CCS' products accelerate development of energy saving industrial automation, wireless and wired communication, automotive, medical device and consumer product applications. Established in 1992, CCS is a Microchip Premier 3rd Party Partner. For more information, please visit http://www.ccsinfo.com.
PIC® MCU, MPLAB® IDE, MPLAB® ICD2, MPLAB® ICD3 and dsPIC® are registered trademarks of Microchip Technology Inc. in the U.S. and other countries.
|
