pbio/drv/sound/sound_ev3: Implement beep-only driver

Author: ArcaneNibble

lib/pbio/drv/sound/sound_ev3.c

@@ -5,18 +5,131 @@
 
 #if PBDRV_CONFIG_SOUND_EV3
 
+#include <math.h>
 #include <stdint.h>
 
-void pbdrv_sound_stop() {
+#include <pbdrv/gpio.h>
+
+#include <tiam1808/ehrpwm.h>
+#include <tiam1808/hw/soc_AM1808.h>
+#include <tiam1808/hw/hw_syscfg0_AM1808.h>
+#include <tiam1808/hw/hw_types.h>
+#include <tiam1808/psc.h>
+
+#include "../drv/gpio/gpio_ev3.h"
+
+// This module covers the frequency range from 64 Hz to 10 kHz.
+// It uses a maximum duty cycle of 1/16, and it controls volume
+// by shortening the duty cycle. The hardware has a resolution
+// of 16 bits for the period counter, and we want 8 bits for the volume,
+// so we use the following timebase division factors to make this work:
+//
+// 64 Hz - 900 Hz   => /40
+// 900 Hz - 8 kHz   => /4
+// 8 kHz - 10 kHz   => /1
 
+// Audio amplifier enable
+static const pbdrv_gpio_t pin_sound_en = PBDRV_GPIO_EV3_PIN(13, 3, 0, 6, 15);
+// Audio output pin
+#define SYSCFG_PINMUX3_PINMUX3_7_4_GPIO0_0 0
+static const pbdrv_gpio_t pin_audio = PBDRV_GPIO_EV3_PIN(3, 7, 4, 0, 0);
+
+void pbdrv_sound_stop() {
+    // Force the output low
+    EHRPWMAQContSWForceOnB(SOC_EHRPWM_0_REGS, EHRPWM_AQCSFRC_CSFB_LOW, EHRPWM_AQSFRC_RLDCSF_IMMEDIATE);
+    // Clean up counter
+    HWREGH(SOC_EHRPWM_0_REGS + EHRPWM_TBCTL) |= EHRPWM_TBCTL_CTRMODE_STOPFREEZE;
+    EHRPWMWriteTBCount(SOC_EHRPWM_0_REGS, 0);
 }
 
 void pbdrv_beep_start(uint32_t frequency, uint16_t sample_attenuator) {
+    // Clamp the frequency into the supported range
+    if (frequency < 64) {
+        frequency = 64;
+    }
+    if (frequency > 10000) {
+        frequency = 10000;
+    }
+
+    // Clamp the volume into the supported range
+    if (sample_attenuator > INT16_MAX) {
+        sample_attenuator = INT16_MAX;
+    }
+    // Extract bits[14:7] for our 8-bit volume resolution
+    sample_attenuator >>= 7;
 
+    // Configure the timebase depending on which bucket the frequency is in.
+    // Don't use EHRPWMTimebaseClkConfig because its calculation algorithm
+    // isn't very good and is also tricky to fix.
+    uint32_t timebase_div;
+    if (frequency < 900) {
+        timebase_div = 40;
+        HWREGH(SOC_EHRPWM_0_REGS + EHRPWM_TBCTL) = (HWREGH(SOC_EHRPWM_0_REGS + EHRPWM_TBCTL) &
+            ~(EHRPWM_TBCTL_CLKDIV | EHRPWM_TBCTL_HSPCLKDIV)) |
+            (EHRPWM_TBCTL_CLKDIV_DIVBY4 << EHRPWM_TBCTL_CLKDIV_SHIFT) |
+            (EHRPWM_TBCTL_HSPCLKDIV_DIVBY10 << EHRPWM_TBCTL_HSPCLKDIV_SHIFT);
+    } else if (frequency < 8000) {
+        timebase_div = 4;
+        HWREGH(SOC_EHRPWM_0_REGS + EHRPWM_TBCTL) = (HWREGH(SOC_EHRPWM_0_REGS + EHRPWM_TBCTL) &
+            ~(EHRPWM_TBCTL_CLKDIV | EHRPWM_TBCTL_HSPCLKDIV)) |
+            (EHRPWM_TBCTL_CLKDIV_DIVBY4 << EHRPWM_TBCTL_CLKDIV_SHIFT) |
+            (EHRPWM_TBCTL_HSPCLKDIV_DIVBY1 << EHRPWM_TBCTL_HSPCLKDIV_SHIFT);
+    } else {
+        timebase_div = 1;
+        HWREGH(SOC_EHRPWM_0_REGS + EHRPWM_TBCTL) = (HWREGH(SOC_EHRPWM_0_REGS + EHRPWM_TBCTL) &
+            ~(EHRPWM_TBCTL_CLKDIV | EHRPWM_TBCTL_HSPCLKDIV)) |
+            (EHRPWM_TBCTL_CLKDIV_DIVBY1 << EHRPWM_TBCTL_CLKDIV_SHIFT) |
+            (EHRPWM_TBCTL_HSPCLKDIV_DIVBY1 << EHRPWM_TBCTL_HSPCLKDIV_SHIFT);
+    }
+
+    // The way that this code controls volume by adjusting the duty cycle
+    // is not linear across the frequency range. For a basic beep driver,
+    // this empirical formula compensates well enough.
+    uint32_t freq_adj = powf(2, log10f(frequency) - 3) * 256;
+
+    uint32_t pwm_period = (SOC_EHRPWM_0_MODULE_FREQ / timebase_div + frequency / 2) / frequency;
+    uint32_t pwm_duty_cycle = (pwm_period * sample_attenuator / 256) / 16 * freq_adj / 256;
+
+    // Program PWM to generate a square wave of this frequency + duty cycle
+    EHRPWMLoadCMPB(SOC_EHRPWM_0_REGS, pwm_duty_cycle, true, 0, true);
+    EHRPWMPWMOpPeriodSet(SOC_EHRPWM_0_REGS, pwm_period, EHRPWM_COUNT_UP, true);
+
+    // Stop forcing output low
+    EHRPWMAQContSWForceOnB(SOC_EHRPWM_0_REGS, 0, EHRPWM_AQSFRC_RLDCSF_IMMEDIATE);
 }
 
 void pbdrv_sound_init() {
+    // Turn on EPWM
+    PSCModuleControl(SOC_PSC_1_REGS, HW_PSC_EHRPWM, PSC_POWERDOMAIN_ALWAYS_ON, PSC_MDCTL_NEXT_ENABLE);
+
+    // The stop function performs various initializations
+    pbdrv_sound_stop();
+
+    // Program EPWM to generate the desired wave shape
+    // Pulse goes high @ t=0
+    // Pulse goes low  @ t=CMPB
+    EHRPWMConfigureAQActionOnB(
+        SOC_EHRPWM_0_REGS,
+        EHRPWM_AQCTLB_ZRO_EPWMXBHIGH,
+        EHRPWM_AQCTLB_PRD_DONOTHING,
+        EHRPWM_AQCTLB_CAU_DONOTHING,
+        EHRPWM_AQCTLB_CAD_DONOTHING,
+        EHRPWM_AQCTLB_CBU_EPWMXBLOW,
+        EHRPWM_AQCTLB_CBD_DONOTHING,
+        EHRPWM_AQSFRC_ACTSFB_DONOTHING
+        );
+    // Disable unused features
+    EHRPWMDBOutput(SOC_EHRPWM_0_REGS, EHRPWM_DBCTL_OUT_MODE_BYPASS);
+    EHRPWMChopperDisable(SOC_EHRPWM_0_REGS);
+    EHRPWMTZTripEventDisable(SOC_EHRPWM_0_REGS, false);
+    EHRPWMTZTripEventDisable(SOC_EHRPWM_0_REGS, true);
 
+    // Configure IO pin mode
+    pbdrv_gpio_alt(&pin_audio, SYSCFG_PINMUX3_PINMUX3_7_4_EPWM0B);
+    // Turn speaker amplifier on
+    // We turn the amplifier on and leave it turned on, because otherwise
+    // it will generate a popping sound whenever it is enabled.
+    pbdrv_gpio_out_high(&pin_sound_en);
 }
 
 #endif // PBDRV_CONFIG_SOUND_EV3