Quick Start Guide for the TC driver

This is the quick start guide for the SAM3/4S/4L/4E/4N/4CM/4C/G Timer Counter (TC) Driver, with step-by-step instructions on how to configure and use the driver for a specific use case.

The code examples can be copied into the main application loop or any other function that will need to control the AST module.

Use Cases

• TC Capture Mode Basic Usage
• TC Waveform Mode Basic Usage

TC Capture Mode Basic Usage

This use case will demonstrate how to initialize the TC module to operate in capture mode using interrupts. Note, that the macros used to select the TC channel are device specific. Refer to the appropriate device-specific datasheet for more information.

Setup Steps

Prerequisites

This module requires the following services:

• System Clock Management (sysclock)
• General Purpose I/O (GPIO) driver

Setup Code

Add these macros to the top of your main application C-file:

• ID_TC_CAPTURE (target TC peripheral ID)
• TC_CHANNEL_CAPTURE (capture channel index)
• TC_Handler mapping for the selected capture channel IRQ

Add this macro and functions to your main application C-file:

#define TC_CAPTURE_TIMER_SELECTION TC_CMR_TCCLKS_TIMER_CLOCK3

static void tc_capture_initialize(void)
{
    /* Configure the PMC to enable the TC module */
    sysclk_enable_peripheral_clock(ID_TC_CAPTURE);
#if SAMG55
    /* Enable PCK output */
    pmc_disable_pck(PMC_PCK_3);
    pmc_switch_pck_to_mck(PMC_PCK_3, PMC_PCK_PRES(0));
    pmc_enable_pck(PMC_PCK_3);
#endif
 
    /* Init TC to capture mode. */
    tc_init(TC, TC_CHANNEL_CAPTURE,
            TC_CAPTURE_TIMER_SELECTION /* Clock Selection */
            | TC_CMR_LDRA_RISING /* RA Loading: rising edge of TIOA */
            | TC_CMR_LDRB_FALLING /* RB Loading: falling edge of TIOA */
            | TC_CMR_ABETRG /* External Trigger: TIOA */
            | TC_CMR_ETRGEDG_FALLING /* External Trigger Edge: Falling edge */
    );
}

void TC_Handler(void)
{
    if ((tc_get_status(TC, TC_CHANNEL_CAPTURE) & TC_SR_LDRBS) == TC_SR_LDRBS) {
        gs_ul_captured_pulses++;
        gs_ul_captured_ra = tc_read_ra(TC, TC_CHANNEL_CAPTURE);
        gs_ul_captured_rb = tc_read_rb(TC, TC_CHANNEL_CAPTURE);
    }
}

Workflow

1. Enable the TC module's capture pin:

   
       ioport_set_pin_mode(PIN_TC_CAPTURE, PIN_TC_CAPTURE_MUX);
       ioport_disable_pin(PIN_TC_CAPTURE);

2. Initialize the capture channel to the following:
   • Load RA on the rising edge of TIOA
   • Load RB on the falling edge of TIOA
   • Set the external trigger to TIOA
   • Set the external trigger to falling edge

         tc_capture_initialize();

3. Enable the TC interrupt using NVIC:

   
       NVIC_DisableIRQ(TC_IRQn);
       NVIC_ClearPendingIRQ(TC_IRQn);
       NVIC_SetPriority(TC_IRQn, 0);
       NVIC_EnableIRQ(TC_IRQn);

4. Enable the capture channel interrupt:

               tc_enable_interrupt(TC, TC_CHANNEL_CAPTURE, TC_IER_LDRBS);

5. In the TC_Handler() function, the load. RB interrupt can be checked by:

       if ((tc_get_status(TC, TC_CHANNEL_CAPTURE) & TC_SR_LDRBS) == TC_SR_LDRBS) {

6. In the TC_Handler() function, the RA value. can be read by:

   uint32_t gs_ul_captured_ra; 

           gs_ul_captured_ra = tc_read_ra(TC, TC_CHANNEL_CAPTURE);

7. In the TC_Handler() function, the RB value. can be read by:

   uint32_t gs_ul_captured_rb; 

           gs_ul_captured_rb = tc_read_rb(TC, TC_CHANNEL_CAPTURE);

TC Waveform Mode Basic Usage

This use case will demonstrate how to initialize the TC module to operate in waveform mode. Note, that the macros used to select the TC channel are device specific. Refer to the appropriate device-specific datasheet for more information.

Setup Steps

Prerequisites

This module requires the following services:

• System Clock Management (sysclock)
• General Purpose I/O (GPIO) driver

Setup Code

Add these macros to the top of your main application C-file:

• ID_TC_WAVEFORM (target TC peripheral ID)
• TC_CHANNEL_WAVEFORM (waveform channel index)

Add these macros and function to your main application C-file:

#define TC_WAVEFORM_TIMER_SELECTION TC_CMR_TCCLKS_TIMER_CLOCK4 

#define TC_WAVEFORM_DIVISOR     128 

#define TC_WAVEFORM_FREQUENCY   178 

#define TC_WAVEFORM_DUTY_CYCLE  30 

static void tc_waveform_initialize(void)
{
 uint32_t ra, rc;
 
 // Configure the PMC to enable the TC module.
 sysclk_enable_peripheral_clock(ID_TC_WAVEFORM);
 
 // Init TC to waveform mode.
 tc_init(TC, TC_CHANNEL_WAVEFORM,
        TC_WAVEFORM_TIMER_SELECTION // Waveform Clock Selection
        | TC_CMR_WAVE       // Waveform mode is enabled
        | TC_CMR_ACPA_SET   // RA Compare Effect: set
        | TC_CMR_ACPC_CLEAR // RC Compare Effect: clear
        | TC_CMR_CPCTRG     // UP mode with automatic trigger on RC Compare
 );
 
 // Configure waveform frequency and duty cycle.
 rc = (sysclk_get_peripheral_bus_hz(TC) /
        TC_WAVEFORM_DIVISOR /
        TC_WAVEFORM_FREQUENCY;
 tc_write_rc(TC, TC_CHANNEL_WAVEFORM, rc);
 ra = (100 - TC_WAVEFORM_FREQUENCY_DUTY_CYCLE * rc / 100;
 tc_write_ra(TC, TC_CHANNEL_WAVEFORM, ra);
 
 // Enable TC TC_CHANNEL_WAVEFORM.
 tc_start(TC, TC_CHANNEL_WAVEFORM);
} 

Workflow

1. Enable the TC module's waveform pin:

   
       ioport_set_pin_mode(PIN_TC_WAVEFORM, PIN_TC_WAVEFORM_MUX);
       ioport_disable_pin(PIN_TC_WAVEFORM);

2. Initialize the waveform channel to the following:
   • Output frequency of 178Hz, with a duty-cycle of 30%
   • Use TC_CMR_TCCLKS_TIMER_CLOCK4, with a divisor of 128

         tc_waveform_initialize();