Enable double buffering

Doesn't work though with new refactored code on S3 device - do not use...

src/ESP32-HUB75-MatrixPanel-I2S-DMA.cpp

@@ -98,6 +98,9 @@ bool MatrixPanel_I2S_DMA::allocateDMAmemory()
     // malloc the DMA linked list descriptors that i2s_parallel will need
     desccount = numDMAdescriptorsPerRow * ROWS_PER_FRAME;
 
+    if (m_cfg.double_buff)
+      dma_bus.enable_double_dma_desc();
+      
     dma_bus.allocate_dma_desc_memory(desccount);
 
 /*

src/platforms/esp32/esp32_i2s_parallel_dma.cpp

@@ -564,6 +564,9 @@ static void IRAM_ATTR irq_hndlr(void* arg) { // if we use I2S1 (default)
         _dmadesc_a[_dmadesc_count-1].qe.stqe_next = &_dmadesc_a[0]; 
         _dmadesc_b[_dmadesc_count-1].qe.stqe_next = &_dmadesc_a[0]; 
     }
+
+    _dmadesc_a_active ^= _dmadesc_a_active;
+    
   } // end flip
 
 

src/platforms/esp32s3/gdma_lcd_parallel16.cpp

@@ -269,7 +269,7 @@
 
   void Bus_Parallel16::enable_double_dma_desc(void)
   {
-    //_double_dma_buffer = true;
+    _double_dma_buffer = true;
   }
 
   // Need this to work for double buffers etc.
@@ -288,8 +288,20 @@
       return false;
     }
 
+    if (_double_dma_buffer)
+    {
+      _dmadesc_b= (HUB75_DMA_DESCRIPTOR_T*)heap_caps_malloc(sizeof(HUB75_DMA_DESCRIPTOR_T) * len, MALLOC_CAP_DMA);
+    
+      if (_dmadesc_b == nullptr)
+      {
+        ESP_LOGE(TAG, "ERROR: Couldn't malloc _dmadesc_b. Not enough memory.");
+        _double_dma_buffer = false;
+      }
+    }
+
+
     _dmadesc_a_idx  = 0;
-   // _dmadesc_b_idx  = 0;
+    _dmadesc_b_idx  = 0;
 
     return true;
 
@@ -311,6 +323,29 @@
       return;
     }
 
+    if (_double_dma_buffer == true && dmadesc_b == true)
+    {
+
+      _dmadesc_b[_dmadesc_b_idx].dw0.owner = DMA_DESCRIPTOR_BUFFER_OWNER_DMA;
+      _dmadesc_b[_dmadesc_b_idx].dw0.suc_eof = 0;
+      _dmadesc_b[_dmadesc_b_idx].dw0.size = _dmadesc_b[_dmadesc_b_idx].dw0.length = size; //sizeof(data);
+      _dmadesc_b[_dmadesc_b_idx].buffer = data; //data;
+
+      if (_dmadesc_b_idx == _dmadesc_count-1) {
+          _dmadesc_b[_dmadesc_b_idx].next =  (dma_descriptor_t *) &_dmadesc_b[0]; 
+      }
+      else {
+          _dmadesc_b[_dmadesc_b_idx].next =  (dma_descriptor_t *) &_dmadesc_b[_dmadesc_b_idx+1]; 
+      }
+
+      _dmadesc_b_idx++;
+
+
+
+    }
+    else
+    {
+
       _dmadesc_a[_dmadesc_a_idx].dw0.owner = DMA_DESCRIPTOR_BUFFER_OWNER_DMA;
       _dmadesc_a[_dmadesc_a_idx].dw0.suc_eof = 0;
       _dmadesc_a[_dmadesc_a_idx].dw0.size = _dmadesc_a[_dmadesc_a_idx].dw0.length = size; //sizeof(data);
@@ -326,6 +361,8 @@
       _dmadesc_a_idx++;
 
 
+    }
+
   } // end create_dma_desc_link
 
   void Bus_Parallel16::dma_transfer_start()
@@ -349,7 +386,23 @@
 
   void Bus_Parallel16::flip_dma_output_buffer()
   {
-   
+
+    if ( _double_dma_buffer == false) return;
+
+    if ( _dmadesc_a_active == true) // change across to everything 'b''
+    {
+       _dmadesc_a[_dmadesc_count-1].next =  (dma_descriptor_t *) &_dmadesc_b[0];       
+       _dmadesc_b[_dmadesc_count-1].next =  (dma_descriptor_t *) &_dmadesc_b[0];       
+    }
+    else
+    {
+       _dmadesc_a[_dmadesc_count-1].next =  (dma_descriptor_t *) &_dmadesc_a[0];       
+       _dmadesc_b[_dmadesc_count-1].next =  (dma_descriptor_t *) &_dmadesc_a[0];   
+    }
+
+    _dmadesc_a_active ^= _dmadesc_a_active;
+
+
     
   } // end flip
 

src/platforms/esp32s3/gdma_lcd_parallel16.hpp

@@ -157,15 +157,11 @@
 
     HUB75_DMA_DESCRIPTOR_T* _dmadesc_a = nullptr;
 
-    // uint32_t _clock_reg_value;
-    // uint32_t _fast_wait = 0;
-
-    //bool    _double_dma_buffer = false;
-    //bool    _dmadesc_a_active   = true;    
-
-    //uint32_t _dmadesc_b_idx  = 0;
+    bool    _double_dma_buffer = false;
+    bool    _dmadesc_a_active   = true;    
+    uint32_t _dmadesc_b_idx  = 0;
   
-    //HUB75_DMA_DESCRIPTOR_T* _dmadesc_b = nullptr;    
+    HUB75_DMA_DESCRIPTOR_T* _dmadesc_b = nullptr;    
 
     esp_lcd_i80_bus_handle_t _i80_bus;