topic Re: Timer and interrupt in Kinetis Microcontrollers

Timer and interrupt

eitanm — Sun, 15 May 2011 20:27:28 GMT

Hi, the following will be the first of possibly many questions I'm going to post here,

Sorry in advance for the noob nature of those questions. If there is a good documentation (other then the reference manual) feel free to kindly point me there.

I'm attempting to make my first steps with the Tower K60, I'm working with uvision\Keil IDE (so no CodeWarrior, and no MQX), all I have is a working Blinky sample..

1. How do I configure the interrupt vector table? I went through ARM's CMSIS NVIC interface, I could not find how-to install a function pointer to be execute on an interrupt event.

2. How do I set a simple timer (I guess PIT ?) to trigger my interrupt handler.

Thanks,

Eitan.

Re: Timer and interrupt

mjbcswitzerland — Mon, 16 May 2011 01:24:31 GMT

Assuming interrup vectors in RAM:

The Cortex M4 core's vector table offset needs to be configured, eg.

VECTOR_TABLE_OFFSET_REG = (RAM_START_ADDRESS); // position the vector table at the bottom of RAM

The interrupt needs to be entered into the table and the Cortex NVIC registers configured with the interrupt's priority and enabled, eg.

// Function used to enter processor interrupts
//
static void fnEnterInterrupt(int iInterruptID, unsigned char ucPriority, void (*InterruptFunc)(void))
{
    unsigned long *ptrIntSet = IRQ0_31_SER_ADD;
    unsigned char *ptrPriority = IRQ0_3_PRIORITY_REGISTER_ADD;
    VECTOR_TABLE *ptrVect;
    void ( **processor_ints )( void );

    ptrVect = (VECTOR_TABLE *)(RAM_START_ADDRESS);
    processor_ints = (void (**)(void))&ptrVect->processor_interrupts;
    processor_ints += iInterruptID;
    *processor_ints = InterruptFunc;

    ptrIntSet += (iInterruptID/32);
    *ptrIntSet = (0x01 << (iInterruptID%32));                            // enable the interrupt

    ptrPriority += iInterruptID;
    *ptrPriority = ucPriority;                                           // define the interrupt's priority
}

Usually the Cortex M4's SYSTICK is used as tick timer (this leaves PITs free for other functions).

However, to configure a PIT0 interrupt the following can be done:

1) Enable clocks to the PIT0 module [SIM_SCG6 |= (SIM_SCGC6_PIT);]

2) Enter the PIT handler [fnEnterInterrupt(irq_PIT0_ID, PIT_int_priority, _PIT0_Interrupt);]

3) Configure and start the PIT0 (see data sheet)

4) Handle the interrupt, eg:

static __interrupt void _PIT0_Interrupt(void)
{
PIT_TFLG0 = PIT_TFLG_TIF; // clear pending interrupts

... other stuff
}

There are various additional developer's tips in the following document - see the appendix: http://www.utasker.com/docs/KINETIS/uTaskerV1.4_Kinetis_demo.pdf

Regards

Mark

Re: Timer and interrupt

eitanm — Mon, 16 May 2011 15:36:17 GMT

Hi,

Thanks for your help!

I'm not sure how to integrate the code you've posted into my environment.

I'm using uVision 4 IDE, the only include file I have is "MK60N512MD100.h", it's a basic CMSIS style interface to the K60 that was created by Freescale. None of your defines are recognized in this header and I'm not

sure how to proceed.

Thanks,

Eitan.

Re: Timer and interrupt

mjbcswitzerland — Mon, 16 May 2011 18:38:39 GMT

Eitan

I have attached the header file that the above code uses - you can look up the defines there and exchange for the defines in your file if you want.

Additional project defines for the chip type used are (with 512k FLASH):

#define SIZE_OF_FLASH (512*1024) // 512k FLASH
#define SIZE_OF_RAM (128 * 1024) // 128k SRAM

Alternatively you can get the complete project (including uVision project) from the uTasker web site (http://www.uTasker.com) - this allows simulation of the Kinetis device, including simulation of the interrupt mechanisms, thus simplifying first steps as well as complete projects.

Regards

Mark