Loads characters 16 at a time in the interrupt callback

Author: delta-G

cores/arduino/Serial.cpp

@@ -58,15 +58,22 @@ void UART::WrapperCallback(uart_callback_args_t *p_args) {
       {
           break;
       }
-      case UART_EVENT_TX_COMPLETE:
-      case UART_EVENT_TX_DATA_EMPTY:
+      case UART_EVENT_TX_COMPLETE:  // TEI interrupt
       {
           if(uart_ptr->txBuffer.available()){
-              uart_ptr->txc = uart_ptr->txBuffer.read_char();
-              R_SCI_UART_Write(&(uart_ptr->uart_ctrl), (uint8_t*)&(uart_ptr->txc) , 1);
-          } else {
+              int idx = 0;
+              while (uart_ptr->txBuffer.available() && (idx < 16)){
+                uart_ptr->txc[idx++] = uart_ptr->txBuffer.read_char();
+              }
+              R_SCI_UART_Write(&(uart_ptr->uart_ctrl), (uint8_t*)(uart_ptr->txc) , idx);
+          } 
+          else {
         	  uart_ptr->tx_done = true;
-          }
+          } 
+        break;
+      }
+      case UART_EVENT_TX_DATA_EMPTY: // TXI interrupt had no more data to write
+      {          
         break;
       }
       case UART_EVENT_RX_CHAR:
@@ -113,12 +120,13 @@ size_t UART::write(uint8_t c) {
 /* -------------------------------------------------------------------------- */  
   if(init_ok) {
 	  while(txBuffer.isFull()){;}
-	  txBuffer.store_char(c);
-	  if(tx_done){
-		  tx_done = false;
-		  txc = txBuffer.read_char();  // clear out the char we just added and send it to start transmission.
-		  R_SCI_UART_Write(&uart_ctrl, (uint8_t*)&txc , 1);
-	  }
+    if (tx_done) {
+      tx_done = false;
+      txc[0] = c;
+      R_SCI_UART_Write(&uart_ctrl, (uint8_t*)txc , 1);
+    } else {
+      txBuffer.store_char(c);
+    }
 	  return 1;
   }
   else {

cores/arduino/Serial.h

@@ -80,7 +80,7 @@ class UART : public arduino::HardwareSerial {
     arduino::SafeRingBufferN<SERIAL_BUFFER_SIZE> txBuffer;
 
     volatile bool tx_done = true;
-    char txc;
+    volatile char txc[BSP_FEATURE_SCI_UART_FIFO_DEPTH];
 
     sci_uart_instance_ctrl_t  uart_ctrl;
     uart_cfg_t                uart_cfg;