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big PWM refactor: drive both LEDs and buzzer from TCC

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This commit is contained in:
Joey Castillo
2021-08-29 17:40:44 -04:00
parent 7dc4b0fdc6
commit 6353d25d46
8 changed files with 120 additions and 76 deletions
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65
watch-library/watch/watch_private.c
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@@ -45,6 +45,71 @@ void _watch_init() {
a4_callback = NULL;
}
void _watch_enable_tcc() {
// clock TCC0 with the main clock (4 or 16 MHz) and enable the peripheral clock.
hri_gclk_write_PCHCTRL_reg(GCLK, TCC0_GCLK_ID, GCLK_PCHCTRL_GEN_GCLK0_Val | GCLK_PCHCTRL_CHEN);
hri_mclk_set_APBCMASK_TCC0_bit(MCLK);
// disable and reset TCC0.
hri_tcc_clear_CTRLA_ENABLE_bit(TCC0);
hri_tcc_wait_for_sync(TCC0, TCC_SYNCBUSY_ENABLE);
hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_SWRST);
hri_tcc_wait_for_sync(TCC0, TCC_SYNCBUSY_SWRST);
// have prescaler divide it down to 1 MHz. we need to know the actual CPU speed to do this.
uint32_t freq = watch_get_cpu_speed();
switch (freq) {
case 4000000:
hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_PRESCALER_DIV4);
break;
case 8000000:
hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_PRESCALER_DIV8);
break;
case 12000000:
// NOTE: this case is here for completeness but the watch library never runs the hardware at 12 MHz.
// If you do, buzzer tones will be out of tune, as we can't evenly divide a 12 MHz clock into 1 MHz.
hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_PRESCALER_DIV16);
break;
case 16000000:
hri_tcc_write_CTRLA_reg(TCC0, TCC_CTRLA_PRESCALER_DIV16);
break;
}
// We're going to use normal PWM mode, which means period is controlled by PER, and duty cycle is controlled by
// each compare channel's value:
// * Buzzer tones are set by setting PER to the desired period for a given frequency, and CC[1] to half of that
// period (i.e. a square wave with a 50% duty cycle).
// * LEDs on CC[2] and CC[3] can be set to any value from 0 (off) to PER (fully on).
hri_tcc_write_WAVE_reg(TCC0, TCC_WAVE_WAVEGEN_NPWM);
// The buzzer will set the period depending on the tone it wants to play, but we have to set some period here to
// get the LED working. Almost any period will do, tho it should be below 20000 (i.e. 50 Hz) to avoid flickering.
hri_tcc_write_PER_reg(TCC0, 4096);
// Set the duty cycle of all pins to 0: LED's off, buzzer not buzzing.
hri_tcc_write_CC_reg(TCC0, 1, 0);
hri_tcc_write_CC_reg(TCC0, 2, 0);
hri_tcc_write_CC_reg(TCC0, 3, 0);
// Enable the TCC
hri_tcc_set_CTRLA_ENABLE_bit(TCC0);
hri_tcc_wait_for_sync(TCC0, TCC_SYNCBUSY_ENABLE);
// enable LED PWM pins (the LED driver assumes if the TCC is on, the pins are enabled)
gpio_set_pin_direction(RED, GPIO_DIRECTION_OUT);
gpio_set_pin_function(RED, PINMUX_PA20F_TCC0_WO6);
gpio_set_pin_direction(GREEN, GPIO_DIRECTION_OUT);
gpio_set_pin_function(GREEN, PINMUX_PA21F_TCC0_WO7);
}
void _watch_disable_tcc() {
// disable all PWM pins
gpio_set_pin_direction(BUZZER, GPIO_DIRECTION_OFF);
gpio_set_pin_function(BUZZER, GPIO_PIN_FUNCTION_OFF);
gpio_set_pin_direction(RED, GPIO_DIRECTION_OFF);
gpio_set_pin_function(RED, GPIO_PIN_FUNCTION_OFF);
gpio_set_pin_direction(GREEN, GPIO_DIRECTION_OFF);
gpio_set_pin_function(GREEN, GPIO_PIN_FUNCTION_OFF);
// disable the TCC
hri_tcc_clear_CTRLA_ENABLE_bit(TCC0);
hri_mclk_clear_APBCMASK_TCC0_bit(MCLK);
}
void _watch_enable_usb() {
// disable USB, just in case.
hri_usb_clear_CTRLA_ENABLE_bit(USB);