diff --git a/cores/esp8266/HardwareSerial.cpp b/cores/esp8266/HardwareSerial.cpp
index 2e93f8aee..78108bee7 100644
--- a/cores/esp8266/HardwareSerial.cpp
+++ b/cores/esp8266/HardwareSerial.cpp
@@ -617,18 +617,15 @@ size_t HardwareSerial::write(uint8_t c) {
     size_t room = uart_get_tx_fifo_room(_uart);
     if(room > 0 && _tx_buffer->empty()) {
         uart_transmit_char(_uart, c);
-        if(room < 10) {
-            uart_arm_tx_interrupt(_uart);
-        }
         return 1;
     }
 
     while(_tx_buffer->room() == 0) {
         yield();
-        uart_arm_tx_interrupt(_uart);
     }
 
     _tx_buffer->write(c);
+    uart_arm_tx_interrupt(_uart);
     return 1;
 }
 
diff --git a/cores/esp8266/cbuf.h b/cores/esp8266/cbuf.h
index fee98a94b..087e7200b 100644
--- a/cores/esp8266/cbuf.h
+++ b/cores/esp8266/cbuf.h
@@ -42,9 +42,6 @@ class cbuf {
             if(_end >= _begin) {
                 return _size - (_end - _begin) - 1;
             }
-            if(_begin == _end) {
-                return _size;
-            }
             return _begin - _end - 1;
         }
 
@@ -62,7 +59,7 @@ class cbuf {
             if(getSize() == 0) return -1;
 
             char result = *_begin;
-            if(++_begin == _bufend) _begin = _buf;
+            _begin = wrap_if_bufend(_begin + 1);
             return static_cast<int>(result);
         }
 
@@ -78,8 +75,7 @@ class cbuf {
                 dst += top_size;
             }
             memcpy(dst, _begin, size_to_read);
-            _begin += size_to_read;
-            if(_begin == _bufend) _begin = _buf;
+            _begin = wrap_if_bufend(_begin + size_to_read);
             return size_read;
         }
 
@@ -87,7 +83,7 @@ class cbuf {
             if(room() == 0) return 0;
 
             *_end = c;
-            if(++_end == _bufend) _end = _buf;
+            _end = wrap_if_bufend(_end + 1);
             return 1;
         }
 
@@ -103,8 +99,7 @@ class cbuf {
                 src += top_size;
             }
             memcpy(_end, src, size_to_write);
-            _end += size_to_write;
-            if(_end == _bufend) _end = _buf;
+            _end = wrap_if_bufend(_end + size_to_write);
             return size_written;
         }
 
@@ -114,6 +109,10 @@ class cbuf {
         }
 
     private:
+        inline char* wrap_if_bufend(char* ptr) {
+            return (ptr == _bufend) ? _buf : ptr;
+        }
+
         size_t _size;
         char* _buf;
         char* _bufend;