Enable speaker sounds

Author: Peque

src/main.c

@@ -12,6 +12,7 @@
 #include "serial.h"
 #include "setup.h"
 #include "solve.h"
+#include "speaker.h"
 #include "speed.h"
 
 static void competition(void);

src/setup.c

@@ -214,7 +214,7 @@ void setup_spi_low_speed(void)
  * @see Reference manual (RM0008) "TIMx functional description" and in
  * particular "PWM mode" section.
  */
-static void setup_pwm(void)
+static void setup_motor_driver(void)
 {
 	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE,
 		       TIM_CR1_DIR_UP);
@@ -248,6 +248,44 @@ static void setup_pwm(void)
 	timer_enable_counter(TIM3);
 }
 
+/**
+ * @brief Setup PWM for the speaker.
+ *
+ * TIM1 is used to generate the PWM signals for the speaker:
+ *
+ * - Configure channel 3 as output GPIO.
+ * - Edge-aligned, up-counting timer.
+ * - Prescale to increment timer counter at TIM1CLK_FREQUENCY_HZ.
+ * - Set output compare mode to PWM1 (output is active when the counter is
+ *   less than the compare register contents and inactive otherwise.
+ * - Disable output compare output (speaker is off by default).
+ * - Enable outputs in the break subsystem.
+ *
+ * @see Reference manual (RM0008) "TIMx functional description" and in
+ * particular "PWM mode" section.
+ */
+static void setup_speaker(void)
+{
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ,
+		      GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_TIM1_CH3);
+
+	rcc_periph_reset_pulse(RST_TIM1);
+
+	timer_set_mode(TIM1, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE,
+		       TIM_CR1_DIR_UP);
+
+	timer_set_prescaler(TIM1,
+			    (rcc_apb2_frequency / TIM1CLK_FREQUENCY_HZ - 1));
+	timer_set_repetition_counter(TIM1, 0);
+	timer_enable_preload(TIM1);
+	timer_continuous_mode(TIM1);
+
+	timer_disable_oc_output(TIM1, TIM_OC3);
+	timer_set_oc_mode(TIM1, TIM_OC3, TIM_OCM_PWM1);
+
+	timer_enable_break_main_output(TIM1);
+}
+
 /**
  * @brief Configure timer to read a quadrature encoder.
  *
@@ -373,7 +411,8 @@ void setup(void)
 	setup_adc1();
 	setup_usart();
 	setup_encoders();
-	setup_pwm();
+	setup_motor_driver();
+	setup_speaker();
 	setup_mpu();
 	setup_systick();
 }

src/setup.h

@@ -26,6 +26,7 @@
 
 /** System clock frequency is set in `setup_clock` */
 #define SYSCLK_FREQUENCY_HZ 72000000
+#define TIM1CLK_FREQUENCY_HZ 1000000
 #define SYSTICK_FREQUENCY_HZ 1000
 #define DRIVER_PWM_PERIOD 1024
 

src/speaker.c

@@ -0,0 +1,66 @@
+#include "speaker.h"
+
+uint8_t BASE_NOTE = 9;
+uint8_t BASE_OCTAVE = 4;
+float BASE_FREQUENCY = 440.;
+uint8_t POSITIONS[8] = {9, 11, 0, 2, 4, 5, 7};
+
+/**
+ * @brief Set the frequency for the speaker.
+ *
+ * Frequency is set modulating the PWM signal sent to the speaker.
+ *
+ * @param[in] hz Frequency, in Hertz.
+ */
+static void speaker_set_frequency(float hz)
+{
+	uint16_t period;
+
+	period = (uint16_t)(TIM1CLK_FREQUENCY_HZ / hz);
+	timer_set_period(TIM1, period);
+	timer_set_oc_value(TIM1, TIM_OC3, period / 2);
+}
+
+/**
+ * @brief Turn on the speaker to play the set frequency.
+ */
+static void speaker_on(void)
+{
+	timer_enable_counter(TIM1);
+	timer_enable_oc_output(TIM1, TIM_OC3);
+}
+
+/**
+ * @brief Turn off the speaker.
+ */
+static void speaker_off(void)
+{
+	timer_disable_counter(TIM1);
+	timer_disable_oc_output(TIM1, TIM_OC3);
+}
+
+/**
+ * @brief Play a note through the speaker.
+ *
+ * Even if this function uses the scientific notation, notes are played with
+ * the concert pitch (standard pitch). That means A above middle C is the
+ * reference note, played at 440 Hz.
+ *
+ * @param[in] note Which note to play, in scientific notation.
+ * @param[in] octave Which octave to play, in scientific notation.
+ * @param[in] accidental Number of semitones to sum to the note.
+ * @param[in] duration Duration of the note, in seconds.
+ */
+void speaker_play(char note, uint8_t octave, int8_t accidental, float duration)
+{
+	int16_t sound;
+	float frequency;
+
+	sound = POSITIONS[note - 'A'] - BASE_NOTE + (octave - BASE_OCTAVE) * 12;
+	sound += accidental;
+	frequency = pow(2, sound / 12.) * BASE_FREQUENCY;
+	speaker_set_frequency(frequency);
+	speaker_on();
+	sleep_ticks((uint32_t)(duration * 1000));
+	speaker_off();
+}

src/speaker.h

@@ -0,0 +1,12 @@
+#ifndef __SPEAKER_H
+#define __SPEAKER_H
+
+#include <math.h>
+
+#include <libopencm3/stm32/timer.h>
+
+#include "setup.h"
+
+void speaker_play(char note, uint8_t octave, int8_t accidental, float duration);
+
+#endif /* __SPEAKER_H */