Allow on-the-fly changes to PWMAudio when possible (#1098)

Also fix crash on PWMAudio::end()

Author: earlephilhower

docs/pwm.rst

@@ -43,10 +43,20 @@ Call before ``PWMAudio::begin()``.
 When running at high sample rates, it is recommended to increase the
 ``bufferWords`` to 32 or higher (i.e. ``pwm.setBuffers(4, 32);`` ).
 
+bool setPin(pin_size_t pin)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Adjusts the pin to connect to the PWM audio output.  Only legal before
+``PWMAudio::begin()``.
+
+bool setStereo(bool stereo)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Adjusts the mono/stereo setting of the PWM audio output.  Only legal before
+``PWMAudio::begin()``.
+
 bool setFrequency(long sampleRate)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Sets the sample frequency, but does not start the PWM device.  Should be called
-before ``PWMAudio::begin`` .
+Sets the sample frequency, but does not start the PWM device (however if the
+device was already running, it will wontinue to run at the new frequency).
 
 bool begin()/begin(long sampleRate)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

libraries/AudioBufferManager/src/AudioBufferManager.cpp

@@ -69,10 +69,12 @@ AudioBufferManager::AudioBufferManager(size_t bufferCount, size_t bufferWords, i
 
 AudioBufferManager::~AudioBufferManager() {
     if (_running) {
+        _running = false;
         for (auto i = 0; i < 2; i++) {
             dma_channel_set_irq0_enabled(_channelDMA[i], false);
-            dma_channel_unclaim(_channelDMA[i]);
             __channelMap[_channelDMA[i]] = nullptr;
+            dma_channel_abort(_channelDMA[i]);
+            dma_channel_unclaim(_channelDMA[i]);
         }
         __channelCount--;
         if (!__channelCount) {
@@ -237,6 +239,9 @@ void AudioBufferManager::flush() {
 }
 
 void __not_in_flash_func(AudioBufferManager::_dmaIRQ)(int channel) {
+    if (!_running) {
+        return;
+    }
     if (_isOutput) {
         if (_active[0] != _silence) {
             _addToList(&_empty, _active[0]);

libraries/PWMAudio/src/PWMAudio.cpp

@@ -35,6 +35,7 @@ PWMAudio::PWMAudio(pin_size_t pin, bool stereo) {
 }
 
 PWMAudio::~PWMAudio() {
+    end();
 }
 
 bool PWMAudio::setBuffers(size_t buffers, size_t bufferWords) {
@@ -46,34 +47,24 @@ bool PWMAudio::setBuffers(size_t buffers, size_t bufferWords) {
     return true;
 }
 
-bool PWMAudio::setFrequency(int newFreq) {
+bool PWMAudio::setPin(pin_size_t pin) {
     if (_running) {
         return false;
     }
-    _freq = newFreq;
+    _pin = pin;
     return true;
 }
 
-void PWMAudio::onTransmit(void(*fn)(void)) {
-    _cb = fn;
+bool PWMAudio::setStereo(bool stereo) {
     if (_running) {
-        _arb->setCallback(_cb);
-    }
-}
-
-bool PWMAudio::begin() {
-    if (_stereo && (_pin & 1)) {
-        // Illegal, need to have consecutive pins on the same PWM slice
-        Serial.printf("ERROR: PWMAudio stereo mode requires pin be even\n");
         return false;
     }
+    _stereo = stereo;
+    return true;
+}
 
-    _running = true;
-    _wasHolding = false;
-
-    if (!_bufferWords) {
-        _bufferWords = 16;
-    }
+bool PWMAudio::setFrequency(int newFreq) {
+    _freq = newFreq;
 
     // Figure out the scale factor for PWM values
     float fPWM = 65535.0 * _freq; // ideal
@@ -90,14 +81,40 @@ bool PWMAudio::begin() {
     pwm_config c = pwm_get_default_config();
     pwm_config_set_clkdiv(&c, clock_get_hz(clk_sys) / fPWM);
     pwm_config_set_wrap(&c, _pwmScale);
-    pwm_init(pwm_gpio_to_slice_num(_pin), &c, true);
+    pwm_init(pwm_gpio_to_slice_num(_pin), &c, _running);
     gpio_set_function(_pin, GPIO_FUNC_PWM);
     pwm_set_gpio_level(_pin, (0x8000 * _pwmScale) >> 16);
     if (_stereo) {
         gpio_set_function(_pin + 1, GPIO_FUNC_PWM);
         pwm_set_gpio_level(_pin + 1, (0x8000 * _pwmScale) >> 16);
     }
 
+    return true;
+}
+
+void PWMAudio::onTransmit(void(*fn)(void)) {
+    _cb = fn;
+    if (_running) {
+        _arb->setCallback(_cb);
+    }
+}
+
+bool PWMAudio::begin() {
+    if (_stereo && (_pin & 1)) {
+        // Illegal, need to have consecutive pins on the same PWM slice
+        Serial.printf("ERROR: PWMAudio stereo mode requires pin be even\n");
+        return false;
+    }
+
+    _running = true;
+    _wasHolding = false;
+
+    if (!_bufferWords) {
+        _bufferWords = 16;
+    }
+
+    setFrequency(_freq);
+
     uint32_t ccAddr = PWM_BASE + PWM_CH0_CC_OFFSET + pwm_gpio_to_slice_num(_pin) * 20;
 
     _arb = new AudioBufferManager(_buffers, _bufferWords, 0x80008000, OUTPUT, DMA_SIZE_32);
@@ -108,9 +125,15 @@ bool PWMAudio::begin() {
 }
 
 void PWMAudio::end() {
-    _running = false;
-    delete _arb;
-    _arb = nullptr;
+    if (_running) {
+        _running = false;
+        pinMode(_pin, OUTPUT);
+        if (_stereo) {
+            pinMode(_pin + 1, OUTPUT);
+        }
+        delete _arb;
+        _arb = nullptr;
+    }
 }
 
 int PWMAudio::available() {

libraries/PWMAudio/src/PWMAudio.h

@@ -25,11 +25,13 @@
 
 class PWMAudio : public Stream {
 public:
-    PWMAudio(pin_size_t pin, bool stereo = false);
+    PWMAudio(pin_size_t pin = 0, bool stereo = false);
     virtual ~PWMAudio();
 
     bool setBuffers(size_t buffers, size_t bufferWords);
     bool setFrequency(int newFreq);
+    bool setPin(pin_size_t pin);
+    bool setStereo(bool stereo = true);
 
     bool begin(long sampleRate) {
         setFrequency(sampleRate);