diff --git a/avr/common/wait_100us.asm b/avr/common/wait_100us.asm
new file mode 100644
index 0000000..abfa7ec
--- /dev/null
+++ b/avr/common/wait_100us.asm
@@ -0,0 +1,27 @@
+; ***************************************************************************
+; copyright   : (C) 2023 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.   *
+; ***************************************************************************
+
+
+
+
+; ---------------------------------------------------------------------------
+; @routine Utils_WaitFor100MicroSecs @global
+;
+; wait for about 100 microsecs.
+;
+; @clobbers r22
+
+Utils_WaitFor100MicroSecs:
+    rcall Utils_WaitFor50MicroSecs
+    rcall Utils_WaitFor50MicroSecs
+    ret
+; @end
+
+
+
diff --git a/avr/common/wait_10us.asm b/avr/common/wait_10us.asm
new file mode 100644
index 0000000..a89e24d
--- /dev/null
+++ b/avr/common/wait_10us.asm
@@ -0,0 +1,25 @@
+; ***************************************************************************
+; copyright   : (C) 2023 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.   *
+; ***************************************************************************
+
+
+
+
+; ---------------------------------------------------------------------------
+; @routine Utils_WaitFor10MicroSecs @global
+;
+; wait for 10 microsecs (minus cycles for call and ret).
+;
+; @clobbers r22
+
+Utils_WaitFor10MicroSecs:
+    Utils_WaitNanoSecs 10000, 7, r22            ; wait for 10us (minus RCALL and RET)
+    ret
+; @end
+
+
diff --git a/avr/common/wait_1ms.asm b/avr/common/wait_1ms.asm
new file mode 100644
index 0000000..cf876c4
--- /dev/null
+++ b/avr/common/wait_1ms.asm
@@ -0,0 +1,47 @@
+; ***************************************************************************
+; copyright   : (C) 2023 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.   *
+; ***************************************************************************
+
+
+
+
+; ---------------------------------------------------------------------------
+; @routine Utils_WaitFor1MilliSec @global
+;
+; wait for about 1ms.
+;
+; @clobbers r22
+
+Utils_WaitFor1MilliSec:
+  push r21
+    ldi r21, 10
+Utils_WaitFor1MilliSec_loop:
+      rcall Utils_WaitFor100MicroSecs  ; (R22)
+      dec r21
+    brne  Utils_WaitFor1MilliSec_loop
+  pop r21
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine Utils_WaitForMilliSecs @global
+;
+; wait for given amount of milliseconds
+; @param r16 number of millisecs to wait
+; @clobbers r22
+
+Utils_WaitForMilliSecs:
+    rcall Utils_WaitFor100MicroSecs  ; (R22)
+    dec r16
+  brne Utils_WaitForMilliSecs
+  ret
+; @end
+
+
diff --git a/avr/common/wait_50us.asm b/avr/common/wait_50us.asm
new file mode 100644
index 0000000..33c4d41
--- /dev/null
+++ b/avr/common/wait_50us.asm
@@ -0,0 +1,24 @@
+; ***************************************************************************
+; copyright   : (C) 2023 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.   *
+; ***************************************************************************
+
+
+
+
+; ---------------------------------------------------------------------------
+; @routine Utils_WaitFor50MicroSecs @global
+;
+; wait for 50 microsecs (minus cycles for call and ret).
+;
+; @clobbers r22
+
+Utils_WaitFor50MicroSecs:
+    Utils_WaitNanoSecs 50000, 7, r22            ; wait for 50us (minus RCALL and RET)
+    ret
+; @end
+