Preet: /* Interrupts on Cortex M3 Core */

2014-02-22T00:49:13Z

‎Interrupts on Cortex M3 Core

Preet at 21:46, 31 August 2012

2012-08-31T21:46:30Z

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== Memory Map ==
LPC Memory map can be accessed by using structures, but the "LPC17xx.h" file may be confusing at first to find your LPC registers. The memory map is accessed by structure names followed by structure members. Let's work through an example in which you are trying to find out how to access PINSEL0 mentioned in your LPC datasheet:
* Open up "'''LPC17xx.h'''" (it is in Project/L0 folder)
* Search for "'''PINSEL0'''"
*: You will see that this is inside a struct called '''LPC_PINCON_TypeDef''':
* Now search for "'''LPC_PINCON_TypeDef'''" with a #define in the same line.
*: You will see that '''LPC_PINCON''' is a pointer of this struct
*: <code>#define '''LPC_PINCON''' ((LPC_PINCON_TypeDef *) LPC_PINCON_BASE) </code>
* You can now access '''PINSEL0''' by :
*: <code>LPC_PINCON->PINSEL0 = XYZ;</code>

At first this may get tedius, but once you get more experience, you won't open the '''LPC17xx.h''' file very often.

=== Example ===
<syntaxhighlight lang="c">
LPC_SC->PCONP |= (1 << 12); // Power up ADC
</syntaxhighlight>

<br/>

== Interrupts on Cortex M3 Core ==
Unlike the LPC12xx (ARM7) processors, the Cortex M3 core saves interrupt context automatically. Hence no interrupt attribute is needed and furthermore, function address doesn't need to be specified into any control registers since interrupt vector is fixed.

The easiest way to define an interrupt function is to:
* Look up Interrupt Names in file '''L0/src/cr_startup_lpc175x.cpp'''
*: Look for declaration of a bunch of functions at this file with keyword '''ALIAS'''
*: For example: <code>UART0_IRQHandler();</code>
* Define this function in one of your source code files.
*: Enclose in '''extern "C"{ }''' tags if you are defining the name in *.cpp file
*: '''extern "C"''' is not needed if you are defining this in *.c file
* Enable the Interrupt using CMS Interrupt API:
*: <code>NVIC_EnableIRQ(UART0_IRQn);</code>

=== Example ===
<syntaxhighlight lang="c">
// Here is the Interrupt Function in a main.cpp file
extern "C"
{
void UART0_IRQHandler()
{
}
}

// Enable Interrupt somewhere in your code:
NVIC_EnableIRQ(UART0_IRQn);

</syntaxhighlight>

@@ Line 23: / Line 23: @@
 The easiest way to define an interrupt function is to:
-*  Look up Interrupt Names in file '''L0/src/cr_startup_lpc175x.cpp'''
+*  Look up Interrupt Names in file '''L0/src/startup.cpp'''
 *:  Look for declaration of a bunch of functions at this file with keyword '''ALIAS'''
 *:  For example: <code>UART0_IRQHandler();</code>

LPC17xx Memory Map & Interrupts - Revision history

Preet: /* Interrupts on Cortex M3 Core */

Preet at 21:46, 31 August 2012