A General to question to registers --Arduino Due

Hardware Arduino Due
#1

Hi there. I try to configure some registers of the SAM3x8E controller.

But I still dont understand something

I want to configure the TC channel control register in order so set the the SWTRG " bit 2 software trigger to 1" in order to get software trigger
I dont understand why i can find many adresses

Address: 0x40080000 (0)[0], 0x40080040 (0)[1], 0x40080080 (0)[2], 0x40084000 (1)[0], 0x40084040 (1)[1],
0x40084080 (1)[2], 0x40088000 (2)[0], 0x40088040 (2)[1], 0x40088080 (2)[2]

A screen shot of the register is attached

is it the right way #define TC1_CCR ((volatile unsigned int *) 0x40080000) // Date sheet page number 897

I want to set SWTERG to 1
Thanks in advance !!

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#2

Where is the problem here?
You have three timercounters:

#define TC0        (0x40080000U) /**< \brief (TC0       ) Base Address */
#define TC1        (0x40084000U) /**< \brief (TC1       ) Base Address */
#define TC2        (0x40088000U) /**< \brief (TC2       ) Base Address */

each of them has 3 channels (see table 37-5 in your linked document) where the offset is 0x00 + channel * 0x40 + 0x00

see hardware/arduino/sam/system/CMSIS/Device/ATMEL/sam3xa/include/component/component_tc.h
and hardware/arduino/sam/system/CMSIS/Device/ATMEL/sam3xa/include/sam3x8e.h
for constant definitions.

1 Like
#3

Just set SWTRG, don't worry about address. Here is an example:

void tmr_setup ()
{
  pmc_enable_periph_clk(TC_INTERFACE_ID + 0 *3 + 0); // clock the TC0 channel 0

  TcChannel * t = &(TC0->TC_CHANNEL)[0] ;            // pointer to TC0 registers for its channel 0
  t->TC_CCR = TC_CCR_CLKDIS ;                        // disable internal clocking while setup regs
  t->TC_IDR = 0xFFFFFFFF ;                           // disable interrupts
  t->TC_SR ;                                         // read int status reg to clear pending
  t->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK1 |           // use TCLK1 (prescale by 2, = 42MHz)
              TC_CMR_WAVE |                          // waveform mode
              TC_CMR_WAVSEL_UP_RC |                  // count-up PWM using RC as threshold
              TC_CMR_EEVT_XC0 |     // Set external events from XC0 (this setup TIOB as output)
              TC_CMR_ACPA_CLEAR | TC_CMR_ACPC_CLEAR |
              TC_CMR_BCPB_CLEAR | TC_CMR_BCPC_CLEAR ;
  
  t->TC_RC = TMR_CNTR;              // counter resets on RC, so sets period in terms of 42MHz clock
  t->TC_RA = TMR_CNTR /2;           // roughly square wave
  t->TC_CMR = (t->TC_CMR & 0xFFF0FFFF) | TC_CMR_ACPA_CLEAR | TC_CMR_ACPC_SET ;  // set clear and set from RA and RC compares
  t->TC_CCR = TC_CCR_CLKEN | TC_CCR_SWTRG ;  // re-enable local clocking and switch to hardware trigger source.  
}
#4

Magician:
Just set SWTRG, don't worry about address. Here is an example:

To use that code, you have worried about, as you selected TC0, channel 0 (which will be the first of the nine addresses he asked for).
Its a nice example demonstrating the use.

Those are the aliases to the nine addresse he asked for:

(TC0->TC_CHANNEL)[0], (TC0->TC_CHANNEL)[1], (TC0->TC_CHANNEL)[2]
(TC1->TC_CHANNEL)[0], (TC1->TC_CHANNEL)[1], (TC1->TC_CHANNEL)[2]
(TC2->TC_CHANNEL)[0], (TC2->TC_CHANNEL)[1], (TC2->TC_CHANNEL)[2]

which can be found in the previous mentioned header files.

I found it very helpful, when reading the documentation, digging through the CMSIS-definitions (grepping for register names or values) to find example data structures.

#5