Dastardly DMA

[Xenoamor]

Hi guys,

I'm trying to use DMA to update a register with the contents of the GPIOD_PDIR.
I'm wanting to use PIR to fix my sampling rate

So far I have this:

DMAChannel dmaChannel0;
volatile uint32_t readBuffer;

void setup() {
	// Set port D as inputs
	pinMode(2,	INPUT);		// #0
	pinMode(14, INPUT);		// #1
	pinMode(7,	INPUT);		// #2
	pinMode(8,	INPUT);		// #3
	pinMode(6,	INPUT);		// #4
	pinMode(20, INPUT);		// #5
	pinMode(21, INPUT);		// #6
	pinMode(5,	INPUT);		// #7
	
		/// SETUP DMA
	dmaChannel0.channel = 0; // Ensure this is DMA channel 0 (Must be same as PIT)
	
	// Source
	dmaChannel0.TCD->SADDR = &GPIOD_PDIR;
	dmaChannel0.TCD->SLAST = 0;
	dmaChannel0.TCD->ATTR_SRC = 2; // 32 bit
	dmaChannel0.TCD->SOFF = 0;
	
	// Destination
	dmaChannel0.TCD->DADDR = &readBuffer;
	dmaChannel0.TCD->DLASTSGA = 0;
	dmaChannel0.TCD->ATTR_SRC = 2; // 32 bit
	dmaChannel0.TCD->DOFF = 0;
	
	// Universal
	dmaChannel0.TCD->NBYTES = 4;
	dmaChannel0.TCD->BITER = 4;
	dmaChannel0.TCD->CITER = 4;
	
	
	DMAMUX0_CHCFG0 = (DMAMUX_SOURCE_ALWAYS0 & 0x3F) | DMAMUX_ENABLE | DMAMUX_TRIG;
	dmaChannel0.enable();
	
		/// SETUP PIT
	// Enable the clock gating to pass F_BUS to PIT
	SIM_SCGC6 |= SIM_SCGC6_PIT;
	
	// Turn on PIT
	PIT_MCR = 0x00;
	
	// Set the period of the timer.  Unit is (1 / 50MHz) = 20ns
	// (period / (1/F_BUS)) - 1
	PIT_LDVAL0 = 15; // 16MHz (3)
	
	// Start the timer
	PIT_TCTRL0 |= PIT_TCTRL_TEN;

}

void loop() {
	
	delay(1000);
	
	Serial.println("------------------------------------------------------------------------");
	Serial.println(digitalReadFast(2));
	//for (int i = 0; i < bufSize; i++)
	{
		Serial.print(readBuffer);
		Serial.print(", ");
	}
	Serial.println("\n------------------------------------------------------------------------");
	
}

However readBuffer is remaining at 0x00. Any ideas?

 

[Xenoamor]

Fixed with:

dmaChannel0.source(GPIOD_PDIR);
dmaChannel0.destination(readBuffer);
	
dmaChannel0.transferSize(4);
dmaChannel0.transferCount(1);

Instead of:

// Source
	dmaChannel0.TCD->SADDR = &GPIOD_PDIR;
	dmaChannel0.TCD->SLAST = 0;
	dmaChannel0.TCD->ATTR_SRC = 2; // 32 bit
	dmaChannel0.TCD->SOFF = 0;
	
	// Destination
	dmaChannel0.TCD->DADDR = &readBuffer;
	dmaChannel0.TCD->DLASTSGA = 0;
	dmaChannel0.TCD->ATTR_SRC = 2; // 32 bit
	dmaChannel0.TCD->DOFF = 0;
	
	// Universal
	dmaChannel0.TCD->NBYTES = 4;
	dmaChannel0.TCD->BITER = 4;
	dmaChannel0.TCD->CITER = 4;

I should stick to Paul's stuff more often