Put HardwareSerial and cbuf methods called from interrupt context in RAM.

This is required per the non-OS SDK doc, which states:
  "Using non-OS SDK, please do not call any function defined with
  ICACHE_FLASH_ATTR in the interrupt handler."

This avoids an "Illegal instruction" exception with epc1 pointing at a valid
instruction (in flash) for one of the moved methods.

cores/esp8266/HardwareSerial.cpp

@@ -116,6 +116,13 @@ int uart_get_debug();
 // ####################################################################################################
 // ####################################################################################################
 
+// These function internals can be used from interrupt handlers to ensure they
+// are in instruction RAM, or anywhere that the uart_nr has been validated.
+#define UART_GET_TX_FIFO_ROOM(uart_nr)     (UART_TX_FIFO_SIZE - ((USS(uart_nr) >> USTXC) & 0xff))
+#define UART_TRANSMIT_CHAR(uart_nr, c)     do { USF(uart_nr) = (c); } while(0)
+#define UART_ARM_TX_INTERRUPT(uart_nr)     do { USIE(uart_nr) |= (1 << UIFE); } while(0)
+#define UART_DISARM_TX_INTERRUPT(uart_nr)  do { USIE(uart_nr) &= ~(1 << UIFE); } while(0)
+
 void ICACHE_RAM_ATTR uart_interrupt_handler(uart_t* uart) {
 
     // -------------- UART 0 --------------
@@ -160,7 +167,7 @@ size_t uart_get_tx_fifo_room(uart_t* uart) {
     if(uart == 0)
         return 0;
     if(uart->txEnabled) {
-        return UART_TX_FIFO_SIZE - ((USS(uart->uart_nr) >> USTXC) & 0xff);
+        return UART_GET_TX_FIFO_ROOM(uart->uart_nr);
     }
     return 0;
 }
@@ -177,7 +184,7 @@ void uart_transmit_char(uart_t* uart, char c) {
     if(uart == 0)
         return;
     if(uart->txEnabled) {
-        USF(uart->uart_nr) = c;
+        UART_TRANSMIT_CHAR(uart->uart_nr, c);
     }
 }
 
@@ -241,7 +248,7 @@ void uart_arm_tx_interrupt(uart_t* uart) {
     if(uart == 0)
         return;
     if(uart->txEnabled) {
-        USIE(uart->uart_nr) |= (1 << UIFE);
+        UART_ARM_TX_INTERRUPT(uart->uart_nr);
     }
 }
 
@@ -249,7 +256,7 @@ void uart_disarm_tx_interrupt(uart_t* uart) {
     if(uart == 0)
         return;
     if(uart->txEnabled) {
-        USIE(uart->uart_nr) &= ~(1 << UIFE);
+        UART_DISARM_TX_INTERRUPT(uart->uart_nr);
     }
 }
 
@@ -536,13 +543,13 @@ void HardwareSerial::setDebugOutput(bool en) {
     }
 }
 
-bool HardwareSerial::isTxEnabled(void) {
+bool ICACHE_RAM_ATTR HardwareSerial::isTxEnabled(void) {
     if(_uart == 0)
         return false;
     return _uart->txEnabled;
 }
 
-bool HardwareSerial::isRxEnabled(void) {
+bool ICACHE_RAM_ATTR HardwareSerial::isRxEnabled(void) {
     if(_uart == 0)
         return false;
     return _uart->rxEnabled;
@@ -604,11 +611,12 @@ void HardwareSerial::flush() {
     if(!_written)
         return;
 
+    const int uart_nr = _uart->uart_nr;
     while(true) {
         {
             InterruptLock il;
             if(_tx_buffer->getSize() == 0 &&
-               uart_get_tx_fifo_room(_uart) >= UART_TX_FIFO_SIZE) {
+               UART_GET_TX_FIFO_ROOM(uart_nr) >= UART_TX_FIFO_SIZE) {
                 break;
             }
         }
@@ -623,15 +631,16 @@ size_t HardwareSerial::write(uint8_t c) {
     _written = true;
 
     bool tx_now = false;
+    const int uart_nr = _uart->uart_nr;
     while(true) {
         {
             InterruptLock il;
             if(_tx_buffer->empty()) {
-                if(uart_get_tx_fifo_room(_uart) > 0) {
+                if(UART_GET_TX_FIFO_ROOM(uart_nr) > 0) {
                     tx_now = true;
                 } else {
                     _tx_buffer->write(c);
-                    uart_arm_tx_interrupt(_uart);
+                    UART_ARM_TX_INTERRUPT(uart_nr);
                 }
                 break;
             } else if(_tx_buffer->write(c)) {
@@ -641,7 +650,7 @@ size_t HardwareSerial::write(uint8_t c) {
         yield();
     }
     if (tx_now) {
-        uart_transmit_char(_uart, c);
+        UART_TRANSMIT_CHAR(uart_nr, c);
     }
     return 1;
 }
@@ -650,26 +659,27 @@ HardwareSerial::operator bool() const {
     return _uart != 0;
 }
 
-void HardwareSerial::_rx_complete_irq(char c) {
+void ICACHE_RAM_ATTR HardwareSerial::_rx_complete_irq(char c) {
     if(_rx_buffer) {
         _rx_buffer->write(c);
     }
 }
 
-void HardwareSerial::_tx_empty_irq(void) {
+void ICACHE_RAM_ATTR HardwareSerial::_tx_empty_irq(void) {
     if(_uart == 0)
         return;
     if(_tx_buffer == 0)
         return;
+    const int uart_nr = _uart->uart_nr;
     size_t queued = _tx_buffer->getSize();
     if(!queued) {
-        uart_disarm_tx_interrupt(_uart);
+        UART_DISARM_TX_INTERRUPT(uart_nr);
         return;
     }
 
-    size_t room = uart_get_tx_fifo_room(_uart);
+    size_t room = UART_GET_TX_FIFO_ROOM(uart_nr);
     int n = static_cast<int>((queued < room) ? queued : room);
     while(n--) {
-        uart_transmit_char(_uart, _tx_buffer->read());
+        UART_TRANSMIT_CHAR(uart_nr, _tx_buffer->read());
     }
 }

cores/esp8266/cbuf.cpp

@@ -0,0 +1,46 @@
+/* 
+ cbuf.cpp - Circular buffer implementation
+ Copyright (c) 2014 Ivan Grokhotkov. All rights reserved.
+ This file is part of the esp8266 core for Arduino environment.
+ 
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include "cbuf.h"
+#include "c_types.h"
+
+size_t ICACHE_RAM_ATTR cbuf::getSize() const {
+    if(_end >= _begin) {
+        return _end - _begin;
+    }
+    return _size - (_begin - _end);
+}
+
+int ICACHE_RAM_ATTR cbuf::read() {
+    if(empty()) return -1;
+
+    char result = *_begin;
+    _begin = wrap_if_bufend(_begin + 1);
+    return result; 
+    return static_cast<int>(result);
+}
+
+size_t ICACHE_RAM_ATTR cbuf::write(char c) {
+     if(full()) return 0;
+
+     *_end = c;
+     _end = wrap_if_bufend(_end + 1);
+     return 1;
+}

cores/esp8266/cbuf.h

@@ -21,7 +21,10 @@
 #ifndef __cbuf_h
 #define __cbuf_h
 
+#include <stddef.h>
 #include <stdint.h>
+#include <string.h>
+
 class cbuf {
     public:
         cbuf(size_t size) :
@@ -32,11 +35,7 @@ class cbuf {
             delete[] _buf;
         }
 
-        size_t getSize() const {
+        size_t getSize() const;
-            if(_end >= _begin) return _end - _begin;
-
-            return _size - (_begin - _end);
-        }
 
         size_t room() const {
             if(_end >= _begin) {
@@ -59,13 +58,7 @@ class cbuf {
             return static_cast<int>(*_begin);
         }
 
-        int read() {
+        int read();
-            if(empty()) return -1;
-
-            char result = *_begin;
-            _begin = wrap_if_bufend(_begin + 1);
-            return static_cast<int>(result);
-        }
 
         size_t read(char* dst, size_t size) {
             size_t bytes_available = getSize();
@@ -83,13 +76,7 @@ class cbuf {
             return size_read;
         }
 
-        size_t write(char c) {
+        size_t write(char c);
-            if(full()) return 0;
-
-            *_end = c;
-            _end = wrap_if_bufend(_end + 1);
-            return 1;
-        }
 
         size_t write(const char* src, size_t size) {
             size_t bytes_available = room();