Support synchronized ADC capture

src/AdvancedADC.cpp

@@ -115,19 +115,17 @@ DMABuffer<Sample> &AdvancedADC::read() {
     return NULLBUF;
 }
 
-int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_samples, size_t n_buffers) {
+int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_samples, size_t n_buffers, bool start_sampling) {
     ADCName instance = ADC_NP;
-
     // Sanity checks.
     if (resolution >= AN_ARRAY_SIZE(ADC_RES_LUT) || (descr && descr->pool)) {
         return 0;
     }
-
     // Clear ALTx pin.
     for (size_t i=0; i<n_channels; i++) {
         adc_pins[i] =  (PinName) (adc_pins[i] & ~(ADC_PIN_ALT_MASK));
     }
-    
+
     // Find an ADC that can be used with these set of pins/channels.
     for (size_t i=0; instance == ADC_NP && i<AN_ARRAY_SIZE(adc_pin_alt); i++) {
         // Calculate alternate function pin.
@@ -188,9 +186,11 @@ int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_sampl
     if (descr->pool == nullptr) {
         return 0;
     }
+
     descr->dmabuf[0] = descr->pool->allocate();
     descr->dmabuf[1] = descr->pool->allocate();
 
+
     // Init and config DMA.
     if (hal_dma_config(&descr->dma, descr->dma_irqn, DMA_PERIPH_TO_MEMORY) < 0) {
         return 0;
@@ -201,6 +201,16 @@ int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_sampl
         return 0;
     }
 
+    sampling_rate = sample_rate;
+    // Start sampling immediately unless start_sampling==false.
+    if (start_sampling) {  
+        return start();
+    }
+
+    return 1;
+}
+
+int AdvancedADC::start() {
     // Link DMA handle to ADC handle, and start the ADC.
     __HAL_LINKDMA(&descr->adc, DMA_Handle, descr->dma);
     if (HAL_ADC_Start_DMA(&descr->adc, (uint32_t *) descr->dmabuf[0]->data(), descr->dmabuf[0]->size()) != HAL_OK) {
@@ -217,7 +227,7 @@ int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_sampl
     if (HAL_TIM_Base_Start(&descr->tim) != HAL_OK) {
         return 0;
     }
-    
+
     return 1;
 }
 
@@ -227,6 +237,12 @@ int AdvancedADC::stop()
     return 1;
 }
 
+void AdvancedADC::clear() {
+    if (descr && descr->pool) {
+        descr->pool->flush();
+    }
+}
+
 AdvancedADC::~AdvancedADC()
 {
     dac_descr_deinit(descr, true);

src/AdvancedADC.h

@@ -46,15 +46,17 @@ class AdvancedADC {
         ~AdvancedADC();
         bool available();
         SampleBuffer read();
-        int begin(uint32_t resolution, uint32_t sample_rate, size_t n_samples, size_t n_buffers);
-        int begin(uint32_t resolution, uint32_t sample_rate, size_t n_samples, size_t n_buffers, size_t n_pins, pin_size_t *pins) {
+        int begin(uint32_t resolution, uint32_t sample_rate, size_t n_samples, size_t n_buffers, bool start_sampling = true);
+        int begin(uint32_t resolution, uint32_t sample_rate, size_t n_samples, size_t n_buffers, size_t n_pins, pin_size_t *pins, bool start_sampling = true) {
             if (n_pins > AN_MAX_ADC_CHANNELS) n_pins = AN_MAX_ADC_CHANNELS;
             for (size_t i = 0; i < n_pins; ++i) {
                 adc_pins[i] = analogPinToPinName(pins[i]);
             }
             n_channels = n_pins;
-            return begin(resolution, sample_rate, n_samples, n_buffers);
+            return begin(resolution, sample_rate, n_samples, n_buffers, start_sampling);
         }
+        void clear();
+        int start();
         int stop();
 };