diff --git a/RingBuff.h b/RingBuff.h
index cc15605..c85a6bf 100644
--- a/RingBuff.h
+++ b/RingBuff.h
@@ -32,7 +32,7 @@
 #define RINGBUFF_WRITE(ringBuff, dataIn) (ringBuff).data[RINGBUFF_MASK(ringBuff) & ringBuff.wrIdx++] = (dataIn)
 #define RINGBUFF_READ(ringBuff)          ((ringBuff).data[RINGBUFF_MASK(ringBuff) & ((ringBuff).rdIdx++)])
 #define RINGBUFF_EMPTY(ringBuff)         ((ringBuff).rdIdx == (ringBuff).wrIdx)
-#define RINGBUFF_FULL(ringBuff)          ((RINGBUFF_MASK(ringBuff) & ringFifo.rdIdx) == (RINGBUFF_MASK(ringBuff) & ringFifo.wrIdx))
+#define RINGBUFF_FULL(ringBuff)          ((RINGBUFF_MASK(ringBuff) & ringBuff.rdIdx) == (RINGBUFF_MASK(ringBuff) & ringBuff.wrIdx))
 #define RINGBUFF_COUNT(ringBuff)         (RINGBUFF_MASK(ringBuff) & ((ringBuff).wrIdx - (ringBuff).rdIdx))
 
 /* Buffer type                                                                  */
diff --git a/SerialSTM_CMSIS.cpp b/SerialSTM_CMSIS.cpp
index 71e4ff2..2ca6070 100644
--- a/SerialSTM_CMSIS.cpp
+++ b/SerialSTM_CMSIS.cpp
@@ -128,6 +128,16 @@ int CSerialPort::availableForReadInt(uint8_t n)
   }
 }
 
+int CSerialPort::availableForWriteInt(uint8_t n)
+{
+  switch (n) {
+    case 1U:
+      return !RINGBUFF_FULL(txBuffer1);
+    default:
+      return false;
+  }
+}
+
 uint8_t CSerialPort::readInt(uint8_t n)
 {
   switch (n) {
diff --git a/Version.h b/Version.h
index 7987a7c..f04229c 100644
--- a/Version.h
+++ b/Version.h
@@ -19,7 +19,7 @@
 #if !defined(VERSION_H)
 #define  VERSION_H
 
-#define VERSION "20201117"
+#define VERSION "20201118"
 
 #endif