Jira 842 UART improvement, PR 266, broke BLE interface.

Root causes:

  1. The uart_fifo_fill doesn't check the FIFO's length
     and failed to send out all data.
  2. Check the FIFO status register before write data
     in FIFO.
  3. Ring buffer pointer variables are not volatile and
     polling mechanism failed to examine the actual
     pointer value being update by foreground task.

File changes:

  1. RingBuffer.h:  Make pointer as volatile.
  2. UARTClass.cpp:  Added checking of FIFO size for
     data Tx.
  3. ns16550.c:  Added routines to h/w status register
     checking.

Author: sgbihu

cores/arduino/RingBuffer.h

@@ -30,9 +30,9 @@ class RingBuffer
 {
 public:
 	uint8_t *_aucBuffer;
-	int _iHead ;
-	int _iTail ;
-	bool _buffer_overflow ;
+	volatile int _iHead ;
+	volatile int _iTail ;
+	volatile bool _buffer_overflow ;
 
 	RingBuffer( void ) ;
 	void store_char( uint8_t c ) ;

cores/arduino/UARTClass.cpp

@@ -168,7 +168,7 @@ int UARTClass::read( void )
 
 void UARTClass::flush( void )
 {
-  while (_tx_buffer->_iHead != _tx_buffer->_iTail); //wait for transmit data to be sent
+  while (_tx_buffer->_iHead != (_tx_buffer->_iTail)); //wait for transmit data to be sent
   // Wait for transmission to complete
   while(!uart_tx_complete(CONFIG_UART_CONSOLE_INDEX));
 }
@@ -183,8 +183,7 @@ size_t UARTClass::write( const uint8_t uc_data )
   {
     // If busy we buffer
     int l = (_tx_buffer->_iHead + 1) % UART_BUFFER_SIZE;
-    while (_tx_buffer->_iTail == l)
-      ; // Spin locks if we're about to overwrite the buffer. This continues once the data is sent
+    while (_tx_buffer->_iTail == l); // Spin locks if we're about to overwrite the buffer. This continues once the data is sent
 
     _tx_buffer->_aucBuffer[_tx_buffer->_iHead] = uc_data;
     _tx_buffer->_iHead = l;
@@ -201,21 +200,29 @@ size_t UARTClass::write( const uint8_t uc_data )
 
 void UARTClass::IrqHandler( void )
 {
-  uint8_t uc_data;
-  int ret;
-  ret = uart_poll_in(CONFIG_UART_CONSOLE_INDEX, &uc_data);
-  
-  while ( ret != -1 ) {
-    _rx_buffer->store_char(uc_data);
+  uart_irq_update(CONFIG_UART_CONSOLE_INDEX);
+  // if irq is Receiver Data Available
+  if(uart_irq_rx_ready(CONFIG_UART_CONSOLE_INDEX))
+  {
+    uint8_t uc_data;
+    int ret;
     ret = uart_poll_in(CONFIG_UART_CONSOLE_INDEX, &uc_data);
+    
+    while ( ret != -1 ) {
+      _rx_buffer->store_char(uc_data);
+      ret = uart_poll_in(CONFIG_UART_CONSOLE_INDEX, &uc_data);
+    }
   }
 
-  // Do we need to keep sending data?
-  if (!uart_irq_tx_ready(CONFIG_UART_CONSOLE_INDEX))
+  // if irq is Transmitter Holding Register
+  if(uart_irq_tx_ready(CONFIG_UART_CONSOLE_INDEX))
   {
-    if (_tx_buffer->_iTail != _tx_buffer->_iHead) {
-      uart_poll_out(CONFIG_UART_CONSOLE_INDEX, _tx_buffer->_aucBuffer[_tx_buffer->_iTail]);
-      _tx_buffer->_iTail = (unsigned int)(_tx_buffer->_iTail + 1) % UART_BUFFER_SIZE;
+    if(_tx_buffer->_iTail != _tx_buffer->_iHead)
+    {
+      int end = (_tx_buffer->_iTail < _tx_buffer->_iHead) ? _tx_buffer->_iHead : UART_BUFFER_SIZE;
+      int l = min(end - _tx_buffer->_iTail, UART_FIFO_SIZE);
+      l = uart_fifo_fill(CONFIG_UART_CONSOLE_INDEX, _tx_buffer->_aucBuffer+_tx_buffer->_iTail, l);
+      _tx_buffer->_iTail = (_tx_buffer->_iTail+l)%UART_BUFFER_SIZE;
     }
     else
     {

system/libarc32_arduino101/drivers/ns16550.c

@@ -340,7 +340,7 @@ unsigned char uart_poll_out(
 	)
 {
 	/* wait for transmitter to ready to accept a character */
-	while ((INBYTE(LSR(which)) & LSR_TEMT) == 0)
+	while ((INBYTE(LSR(which)) & LSR_THRE) == 0)
 		;
 
 	OUTBYTE(THR(which), outChar);
@@ -352,6 +352,8 @@ unsigned char uart_poll_out(
 *
 * uart_fifo_fill - fill FIFO with data
 *
+* It is up to the caller to make sure that FIFO capcity is not exceeded
+*
 * RETURNS: number of bytes sent
 */
 
@@ -362,8 +364,9 @@ int uart_fifo_fill(int which, /* UART on which to send */
 {
 	int i;
 
-	for (i = 0; i < size && (INBYTE(LSR(which)) &
-			LSR_BOTH_EMPTY) != 0; i++) {
+	for (i = 0; i < size  && (INBYTE(LSR(which)) &
+			LSR_BOTH_EMPTY) != 0; i++) 
+	{
 		OUTBYTE(THR(which), txData[i]);
 	}
 	return i;
@@ -622,7 +625,6 @@ void uart_int_connect(int which,	   /* UART to which to connect */
 		      )
 {
 	interrupt_connect((unsigned int)uart[which].irq, isr);
-    interrupt_priority_set ((int)uart[which].irq, uart[which].intPri);
 	interrupt_enable((unsigned int)uart[which].irq);
 	/* set the Host Processor Interrupt Routing Mask */
 	SOC_UNMASK_INTERRUPTS(INT_UART_0_MASK + (which * UART_REG_ADDR_INTERVAL));
@@ -641,6 +643,19 @@ uint8_t uart_tx_complete(int which)
 	return INBYTE(LSR(which)) & LSR_TEMT;
 }
 
+/*******************************************************************************
+*
+* uart_tx_complete - check if tx holding register is empty
+*
+* RETURNS: zero if register is non-empty, 
+*          non-zero if register is empty (ready to receive new data)
+*/
+
+uint8_t uart_tx_ready(int which)
+{
+	return INBYTE(LSR(which)) & LSR_THRE;
+}
+
 /*******************************************************************************
 *
 * uart_loop_enable - enable loopback