Tone implementation

cores/arduino/Tone.cpp

@@ -0,0 +1,132 @@
+/*
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+    See the GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+
+    Tone implementation for the Arduino Due / SAM boards, written by Mikhail Khrenov
+    (@redrussianbear, mkhrenov) on 2020/06/25, based on Tone for SAMD boards, with
+    info on Due Timer Counters taken from "Arduino Due Timers" by Jeff ko7m.
+*/
+
+#include "Tone.h"
+#include <Arduino.h>
+
+#include "variant.h"
+
+static uint32_t last_output_pin = -1;
+
+static volatile Pio *port_pio_registers;
+static volatile uint32_t port_bitmask;
+static volatile int64_t toggleCount;
+static volatile bool tone_is_active = false;
+
+// Timer Counter names, Interrupt Request handlers, channel
+#define TONE_TC         TC1
+#define TONE_TC_IRQn    TC5_IRQn
+#define TONE_TC_PMC     ID_TC5
+#define TONE_TC_CHANNEL 2
+
+// Map TC5_Handler to tone_handler to run pin toggling interrupt
+void TC5_Handler(void) __attribute__ ((weak, alias("tone_handler")));
+
+void tone(uint32_t outputPin, uint32_t frequency, uint32_t duration) {
+    // Avoid divide by zero error by calling 'noTone' instead
+    if (frequency == 0) {
+        noTone(outputPin);
+        return;
+    }
+
+    // Disable and clear existing interrupt requests
+    NVIC_DisableIRQ(TONE_TC_IRQn);
+    NVIC_ClearPendingIRQ(TONE_TC_IRQn);
+
+    NVIC_SetPriority(TONE_TC_IRQn, 0);
+
+    // Turn off Power Management Controller protections and enable peripheral clock
+    pmc_set_writeprotect(false);
+    pmc_enable_periph_clk(TONE_TC_PMC);
+
+    TC_Configure(TONE_TC, TONE_TC_CHANNEL, TC_CMR_WAVE | TC_CMR_WAVSEL_UP_RC | TC_CMR_TCCLKS_TIMER_CLOCK3);
+
+    // If swapping pins, disable tone on old pin
+    if (tone_is_active && (outputPin != last_output_pin))
+        noTone(last_output_pin);
+
+    // If swapping pins, record and set initial state low
+    if (outputPin != last_output_pin) {
+        last_output_pin = outputPin;
+        digitalWrite(outputPin, LOW);
+        pinMode(outputPin, OUTPUT);
+        tone_is_active = true;
+    }
+
+    // Compute total number of toggles to finish duration, if duration is zero or less set to -1 (indefinite)
+    toggleCount = duration > 0 ? duration * frequency / 1000 : -1;
+
+
+    // Retrieve PIO registers for required output pin, store in globals
+    port_pio_registers = g_APinDescription[outputPin].pPort;
+    port_bitmask = g_APinDescription[outputPin].ulPin;
+
+    // Set register A to got high at 50% period, register C to go low at 100% period
+    uint32_t cutoff = VARIANT_MCK / 32 / frequency;
+    cutoff &= ~0x00000001U; // Ensure low and high periods are equal by enforcing even cutoff
+    TC_SetRA(TONE_TC, TONE_TC_CHANNEL, cutoff / 2);
+    TC_SetRC(TONE_TC, TONE_TC_CHANNEL, cutoff);
+
+    TC_Start(TONE_TC, TONE_TC_CHANNEL);
+
+    // Enable register C and A compare interrupts, disable all others
+    TONE_TC->TC_CHANNEL[TONE_TC_CHANNEL].TC_IER = TC_IER_CPCS | TC_IER_CPAS;
+    TONE_TC->TC_CHANNEL[TONE_TC_CHANNEL].TC_IDR = ~(TC_IER_CPCS | TC_IER_CPAS);
+
+    NVIC_EnableIRQ(TONE_TC_IRQn);
+}
+
+void noTone(uint32_t outputPin) {
+    TC_Stop(TONE_TC, TONE_TC_CHANNEL);
+    digitalWrite(outputPin, LOW);
+    tone_is_active = false;
+}
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+// Bound to TC5_Handler above
+void tone_handler(void) {
+    // Clear the interrupt
+    TC_GetStatus(TONE_TC, TONE_TC_CHANNEL);
+
+    if (toggleCount != 0) {
+        // Toggle the ouput pin
+        if (port_pio_registers->PIO_ODSR & port_bitmask) {
+            // If high, go low
+            port_pio_registers->PIO_CODR = port_bitmask;
+        } else {
+            // Else, go high
+            port_pio_registers->PIO_SODR = port_bitmask;
+        }
+
+        if (toggleCount > 0)
+            toggleCount--;
+    } else {
+        TC_Stop(TONE_TC, TONE_TC_CHANNEL);
+        port_pio_registers->PIO_CODR = port_bitmask;         // Take pin low
+        tone_is_active = false;
+    }
+}
+
+#ifdef __cplusplus
+}
+#endif