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

Also fix crash on PWMAudio::end()

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) {
@@ -46,11 +47,48 @@ 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;
     }
+    _pin = pin;
+    return true;
+}
+
+bool PWMAudio::setStereo(bool stereo) {
+    if (_running) {
+        return false;
+    }
+    _stereo = stereo;
+    return true;
+}
+
+bool PWMAudio::setFrequency(int newFreq) {
     _freq = newFreq;
+
+    // Figure out the scale factor for PWM values
+    float fPWM = 65535.0 * _freq; // ideal
+
+    if (fPWM > clock_get_hz(clk_sys)) {
+        // Need to downscale the range to hit the frequency target
+        float pwmMax = (float) clock_get_hz(clk_sys) /(float) _freq;
+        _pwmScale = pwmMax;
+        fPWM = clock_get_hz(clk_sys);
+    } else {
+        _pwmScale = 1 << 16;
+    }
+
+    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, _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;
 }
 
@@ -75,28 +113,7 @@ bool PWMAudio::begin() {
         _bufferWords = 16;
     }
 
-    // Figure out the scale factor for PWM values
-    float fPWM = 65535.0 * _freq; // ideal
-
-    if (fPWM > clock_get_hz(clk_sys)) {
-        // Need to downscale the range to hit the frequency target
-        float pwmMax = (float) clock_get_hz(clk_sys) /(float) _freq;
-        _pwmScale = pwmMax;
-        fPWM = clock_get_hz(clk_sys);
-    } else {
-        _pwmScale = 1 << 16;
-    }
-
-    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);
-    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);
-    }
+    setFrequency(_freq);
 
     uint32_t ccAddr = PWM_BASE + PWM_CH0_CC_OFFSET + pwm_gpio_to_slice_num(_pin) * 20;
 
@@ -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);