Microchip Technology dsPIC33F Family Manual de usuario descargar pdf (Pagina 10)

dsPIC33F Family Reference Manual

Example 12-2 provides sample code that transfers the capture values to RAM with DMA.

DMA Channel 0 is set up for the Input Capture module with the following configuration:

• Transfer data from the Input Capture module to RAM

• One-shot operating mode

• Register Indirect with Post-Increment addressing

• Single buffer

• 256 transfers per buffer

• Transfer words

Example 12-2: Input Capture with DMA

12.5.3 Capture Pin as External Interrupt

The Input Capture (ICx) pin can be used as an auxiliary external interrupt source by clearing the

Input Capture Interrupt (ICI = 00) bits. In this condition an interrupt is generated on every capture

event, and the FIFO overflow condition does not inhibit the capture interrupt. Consequently, the

input capture buffer need not be read in the Capture Interrupt Service Routine (ISR). The Input

Capture Mode (ICM<2:0>) bits can be used to select the edge polarity for the interrupt.

// Initialize Capture module

IC1CONbits.ICM = 0b00; // Disable Input Capture 1 module

IC1CONbits.ICTMR = 1; // Select Timer2 as the IC1 Time base

IC1CONbits.ICI = 0b00; // Interrupt on every second capture event

IC1CONbits.ICM = 0b001; // Generate capture event on every Rising edge

Setup DMA for Input Capture:

// Define Buffer in DMA RAM

unsigned int BufferA[256] __attribute__((space(dma)));

DMA0CONbits.AMODE = 0b00; // Register indirect with post increment

DMA0CONbits.MODE = 0b01; // One Shot, Ping-Pong mode Disabled

DMA0CONbits.DIR = 0; // Peripheral to RAM

DMA0PAD = (int)&IC1BUF; // Address of the capture buffer register

DMA0REQ = 1;// Select IC module as DMA request source

DMA0CNT = 255; // Number of words to buffer

DMA0STA = __builtin_dmaoffset(&BufferA);

IFS0bits.DMA0IF = 0; // Clear the DMA interrupt flag bit

IEC0bits.DMA0IE = 1; // Enable DMA interrupt enable bit

DMA0CONbits.CHEN = 1;

Setup DMA Interrupt Handler

void __attribute__((__interrupt__)) _DMA0Interrupt(void)

{

// Process the captured values

IFS0bits.DMA0IF = 0; // Clear the DMA0 Interrupt Flag

}

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Microchip Technology dsPIC33F Family Manual de usuario Pagina 10