diff --git a/acpi/README.md b/acpi/README.md
new file mode 100644
index 0000000..12baf77
--- /dev/null
+++ b/acpi/README.md
@@ -0,0 +1,30 @@
+# Use iMac powerbutton to toggle TDM
+
+Since the powerbutton is the only physical button on the iMac, the following instructions allow using the powerbutton to toggle TDM (and to switch off the iMac as well, of course). No more keyboard/mouse are needed and the iMac can be used as an external monitor.
+
+How it works:
+- After boot, iMac starts in TDM mode
+- One press of the power button toggles TDM mode
+- Two presses of the power button (within 1 second) switches off the iMac
+
+# How to use
+
+Install by following the instructions in the main README file
+
+Upon startup, switch TDM on:
+```
+cp rc.local /etc/rc.local
+```
+
+Add acpi powerbutton event and script to handle event:
+```
+cp powerbutton /etc/acpi/events
+cp powerbutton.sh /etc/acpi
+```
+
+Restart acpid
+```
+systemctl restart acpid
+```
+
+_Note_: This was tested on a end-2009 27" iMac running Ubuntu 20.10
diff --git a/acpi/powerbutton b/acpi/powerbutton
new file mode 100644
index 0000000..9028e62
--- /dev/null
+++ b/acpi/powerbutton
@@ -0,0 +1,2 @@
+event=button/power PBTN
+action=/etc/acpi/powerbutton.sh
diff --git a/acpi/powerbutton.sh b/acpi/powerbutton.sh
new file mode 100755
index 0000000..c49b318
--- /dev/null
+++ b/acpi/powerbutton.sh
@@ -0,0 +1,30 @@
+#!/bin/bash
+
+pushd $(dirname "${BASH_SOURCE[0]}")
+
+FILE=powerbutton_pressed
+NOW=$(date +%s)
+
+if [[ -f "$FILE" ]]; then
+  # Read timestamp of previous powerbutton press from file
+  echo "File exists"
+  typeset -i PREV=$(cat $FILE)
+  echo Compare $NOW and $PREV
+
+  # if two powerbutton presses were <1 seconds apart -> shutdown
+  if [[ $(($NOW-$PREV)) -lt 2 ]]; then
+    # Shutdown
+    echo "Powerbutton pressed twice in a row: Shutting down"
+    shutdown now
+  else
+    echo "Toggle TDM"
+    /home/freek/smc_util/tdm_toggle.sh &
+  fi
+else
+  echo "Toggle TDM"
+  /home/freek/smc_util/tdm_toggle.sh &
+fi
+
+echo $NOW > $FILE
+
+popd
diff --git a/acpi/rc.local b/acpi/rc.local
new file mode 100755
index 0000000..50d5a74
--- /dev/null
+++ b/acpi/rc.local
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# Start Target Display Mode such that the pc is used as external monitor right away
+# Note: The Power button toggles TDM (see /etc/acpi/events)
+pushd /home/freek/smc_util
+./tdm_on.sh
+popd
diff --git a/tdm_off.sh b/tdm_off.sh
index 8081460..bc5fb92 100755
--- a/tdm_off.sh
+++ b/tdm_off.sh
@@ -1,4 +1,5 @@
 #!/bin/bash
+rm -f tdm_started
 ./SmcDumpKey MVHR 0
 sleep 1
 ./SmcDumpKey MVMR 2
diff --git a/tdm_on.sh b/tdm_on.sh
index 9fd8ffe..508f1c8 100755
--- a/tdm_on.sh
+++ b/tdm_on.sh
@@ -4,3 +4,4 @@ sleep 1
 ./SmcDumpKey MVMR 2
 sleep 2
 DISPLAY=:0.0 xrandr --output eDP --off
+touch tdm_started
diff --git a/tdm_toggle.sh b/tdm_toggle.sh
new file mode 100755
index 0000000..8a1a46a
--- /dev/null
+++ b/tdm_toggle.sh
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+pushd $(dirname "${BASH_SOURCE[0]}")
+
+if [[ -f "tdm_started" ]]; then
+  echo "Switching off TDM"
+  source tdm_off.sh
+else
+  echo "Switch on TDM"  
+  source tdm_on.sh
+fi
+
+popd