diff --git a/avr/common/0BUILD b/avr/common/0BUILD
index 9efb948..bcc931c 100644
--- a/avr/common/0BUILD
+++ b/avr/common/0BUILD
@@ -4,6 +4,7 @@
 
   <extradist>
     crc8.asm
+    m_ringbuffer.asm
     ringbuffer.asm
     shared.asm
     utils.asm
diff --git a/avr/common/m_ringbuffer.asm b/avr/common/m_ringbuffer.asm
new file mode 100644
index 0000000..d189f9e
--- /dev/null
+++ b/avr/common/m_ringbuffer.asm
@@ -0,0 +1,114 @@
+; ***************************************************************************
+; copyright   : (C) 2025 by Martin Preuss
+; email       : martin@libchipcard.de
+;
+; ***************************************************************************
+; * This file is part of the project "AqHome".                              *
+; * Please see toplevel file COPYING of that project for license details.   *
+; ***************************************************************************
+
+
+
+; ---------------------------------------------------------------------------
+; @macro m_ringbuffer_y_writebyte
+;
+; @param R16 byte to write
+; @param Y   base address (for "LDD Y+nn" and "STD Y+nn")
+; @param %0 constant maxBytes
+; @param %1 offset to Y to access usedBytes variable (for "LDD Y+nn" and "STD Y+nn")
+; @param %2 offset to Y to access readPos variable
+; @param %3 offset to Y to access writePos variable
+; @param %4 offset to Y to access buffer
+; @return CFLAG set if okay, cleared on error (i.e. buffer full)
+; @clobbers R17, X
+
+.macro m_ringbuffer_y_writebyte
+  ldd r17, Y+@1 ; usedBytes
+  cpi r17, @0   ; maxBytes
+  brcc l_end
+  inc r17
+  std Y+@1, r17 ; usedBytes
+  ldd r17, Y+@3 ; writePos
+  mov xl, yl
+  mov xh, yh
+  adiw xh:xl, @4
+  add xl, r17
+  adc xh, r17
+  sub xh, r17
+  st X, r16
+  inc r17
+  cpi r17, @0
+  brcs l_store
+  clr r17
+l_store:
+  std Y+@3, r17 ; writePos
+  sec
+l_end:
+.endmacro
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @macro m_ringbuffer_y_readbyte
+;
+; @param Y   base address (for "LDD Y+nn" and "STD Y+nn")
+; @param %0 constant maxBytes
+; @param %1 offset to Y to access usedBytes variable (for "LDD Y+nn" and "STD Y+nn")
+; @param %2 offset to Y to access readPos variable
+; @param %3 offset to Y to access writePos variable
+; @param %4 offset to Y to access buffer
+; @return CFLAG set if okay, cleared on error (i.e. buffer full)
+; @return R16 byte read
+; @clobbers R17, X
+
+.macro m_ringbuffer_y_readbyte
+  ldd r17, Y+@1 ; usedBytes
+  tst r17
+  clc
+  breq l_end
+  dec r17
+  std Y+@1, r17 ; usedBytes
+  ldd r17, Y+@2 ; readPos
+  mov xl, yl
+  mov xh, yh
+  adiw xh:xl, @4
+  add xl, r17
+  adc xh, r17
+  sub xh, r17
+  ld r16, X
+  inc r17
+  cpi r17, @0
+  brcs l_store
+  clr r17
+l_store:
+  std Y+@2, r17 ; readPos
+  sec
+l_end:
+.endmacro
+
+
+
+; ---------------------------------------------------------------------------
+; @macro m_ringbuffer_y_reset
+;
+; @param Y   base address (for "LDD Y+nn" and "STD Y+nn")
+; @param %0 constant maxBytes
+; @param %1 offset to Y to access usedBytes variable (for "LDD Y+nn" and "STD Y+nn")
+; @param %2 offset to Y to access readPos variable
+; @param %3 offset to Y to access writePos variable
+; @param %4 offset to Y to access buffer
+; @clobbers R17
+
+.macro m_ringbuffer_y_reset
+  clr r17
+  std Y+@1, r17 ; usedBytes
+  std Y+@2, r17 ; readPos
+  std Y+@3, r17 ; writePos
+l_end:
+.endmacro
+; @end
+
+
+
+