diff --git a/content/SUMMARY.md b/content/SUMMARY.md
index 00147f1..216a910 100644
--- a/content/SUMMARY.md
+++ b/content/SUMMARY.md
@@ -5,6 +5,7 @@
     - [ArduPilot](ardupilot/index.md)
         - [ArduPilot recommended settings](ardupilot/ardupilot-recommended-settings.md)
         - [ArduPilot setup checklist](ardupilot/ardupilot-setup-checklist.md)
+        - [Bitmask calculator](ardupilot/bitmask-calculator.md)
         - [Building ArduPilot](ardupilot/building-ardupilot.md)
         - [Configuring a switch as a relay](ardupilot/configuring-a-switch-as-a-relay.md)
         - [DJI FPV configuration](ardupilot/dji-fpv-configuration.md)
diff --git a/content/ardupilot/bitmask-calculator.md b/content/ardupilot/bitmask-calculator.md
new file mode 100644
index 0000000..e8b58cc
--- /dev/null
+++ b/content/ardupilot/bitmask-calculator.md
@@ -0,0 +1,160 @@
+# Bitmask calculator
+
+<style>
+    div.box{
+        width: 90%;
+    }
+	table {
+		border: 1px solid #222;
+	}
+</style>
+<script type="text/javascript">
+function dec2bin(dec) {
+    return reverse((dec >>> 0).toString(2));
+}
+function reverse(str) {
+    return str.split("").reverse().join("");
+}
+
+var bitmaskDescArr = [];
+
+function loadBitmask(){
+    url = document.getElementById("built").value;
+
+	if (url == ""){
+        return;
+    }
+
+    fetch(url)
+    .then(response => response.text())
+    .then(data => {
+        const parser = new DOMParser();
+        const xml = parser.parseFromString(data, "application/xml");
+
+        var params = xml.getElementsByTagName("param");
+		console.log(params);
+
+		for (var i = 0; i < params.length; i++) {
+            var param = params[i].attributes.name.nodeValue;		//works, param name
+
+
+            if(params[i].childNodes[1]){
+                if( typeof params[i].childNodes[1].attributes.name == "object"){
+                    if(params[i].childNodes[1].attributes.name.nodeValue && params[i].childNodes[1].attributes.name.nodeValue == "Bitmask"){
+
+// 						// populate dropdown
+                        var paramSelect = document.getElementById("paramSelect");
+                        var el = document.createElement("option");
+                        el.textContent = param.replace("ArduPlane:","");
+                        el.value = param;
+                        paramSelect.appendChild(el);
+
+                        var bitmaskDescTxt = params[i].textContent.trim();
+                        bitmaskDescArr[param] = bitmaskDescTxt.split(',');
+
+                    }
+                }
+            }
+        }
+    })
+    .catch(console.error);
+}
+
+function bitbox(bit){
+    dec = parseInt(document.getElementById("decimal").value);
+    if(document.getElementById(bit).checked == true){
+        dec += parseInt(bit);
+    }else{
+        dec -= parseInt(bit);
+    }
+    document.getElementById("decimal").value = dec;
+    parseBitmask();
+}
+
+function parseBitmask() {
+    console.log("found "+Object.keys(bitmaskDescArr).length+" bitmask parameters");
+
+    document.getElementById("result").innerHTML="";
+    var tbl = document.createElement('table');
+    tbl.style="border: 1px solid #222";
+    var tbdy = document.createElement('tbody');
+
+    dec = document.getElementById("decimal").value;
+    binary=dec2bin(document.getElementById("decimal").value);
+    var param = document.getElementById("paramSelect").value;
+
+    for (var bit = 0; bit < bitmaskDescArr[param].length; bit++) {
+        var val = binary[bit];
+
+        var tr = document.createElement('tr');
+
+        var td = document.createElement('td');
+        td.style="border: 1px solid black;";
+        var singleBitDecvalue = Math.pow(2,bit);	// convert the bit to a decimal
+        var checkbox = document.createElement('input');
+        checkbox.type = "checkbox";
+        checkbox.name = "name";
+        checkbox.value = "checked";
+        checkbox.id = singleBitDecvalue;
+        checkbox.setAttribute("onclick","bitbox("+singleBitDecvalue+")");
+
+        if (val == "1"){
+            checkbox.checked = true;
+        }else{
+            checkbox.checked = false;
+        }
+        td.appendChild(checkbox);
+        tr.appendChild(td);
+
+
+        var td = document.createElement('td');
+        td.appendChild(document.createTextNode(bitmaskDescArr[param][bit]));
+
+        if (val == "1"){
+            td.style  = "border: 1px solid black; color: green";
+        }else{
+            td.style  = "border: 1px solid black; color: red";
+        }
+        tr.appendChild(td);
+
+        var td = document.createElement('td');
+        td.style="border: 1px solid black; color: grey";
+        td.appendChild(document.createTextNode(Math.pow(2,bit)));
+        tr.appendChild(td);
+
+        tbdy.appendChild(tr);
+        tbl.appendChild(tbdy);
+    }
+     document.getElementById("result").appendChild(tbl);
+}
+
+
+</script>
+
+<div class="box">
+    <div id="input">
+        <select id="built" onChange="loadBitmask();">
+            <option value="">select your build</option>
+            <option value='https://arducustom.github.io/v/dev/ArduPlane/apm.pdef.xml'>ArduCustom master</option>
+            <option value='https://arducustom.github.io/v/10.0/ArduPlane/apm.pdef.xml'>ArduCustom v10</option>
+            <option value='https://arducustom.github.io/v/9.0/ArduPlane/apm.pdef.xml'>ArduCustom v9.0</option>
+            <!-- <option value='https://autotest.ardupilot.org/Parameters/ArduPlane/apm.pdef.xml'>ArduPlane offical master</option> -->
+        </select>
+        <select id="paramSelect" onChange="parseBitmask();">
+        </select>
+        <input type="text" id="decimal" value="1" oninput="parseBitmask();">
+    </div>
+    <br>
+    <div id="result">
+    </div>
+</div>
+
+
+_(Many thanks to mfoos for writing this note.)_
+
+* * *
+
+<p style="font-size:80%; font-style: italic">
+Last updated on August 13, 2022. For any questions/feedback,
+email me at <a href="mailto:hi@stavros.io">hi@stavros.io</a>.
+</p>
diff --git a/content/ardupilot/index.md b/content/ardupilot/index.md
index 1454959..3d09b06 100644
--- a/content/ardupilot/index.md
+++ b/content/ardupilot/index.md
@@ -4,6 +4,7 @@ Click on a link in the list below to go to that page:
 
 1. [ArduPilot recommended settings](../../ardupilot/ardupilot-recommended-settings.html)
 1. [ArduPilot setup checklist](../../ardupilot/ardupilot-setup-checklist.html)
+1. [Bitmask calculator](../../ardupilot/bitmask-calculator.html)
 1. [Building ArduPilot](../../ardupilot/building-ardupilot.html)
 1. [Configuring a switch as a relay](../../ardupilot/configuring-a-switch-as-a-relay.html)
 1. [DJI FPV configuration](../../ardupilot/dji-fpv-configuration.html)
diff --git a/content/ardupilot/transfer-config-between-craft.md b/content/ardupilot/transfer-config-between-craft.md
index 8de8a88..25c8000 100644
--- a/content/ardupilot/transfer-config-between-craft.md
+++ b/content/ardupilot/transfer-config-between-craft.md
@@ -7,7 +7,7 @@ parachute restore -f "^(ACRO_LOCKING|OSD.*|RC[\d_]+.*|\
     FLTMODE.*|FLIGHT_OPTIONS|FS_.*|RTL_CLIMB_MIN|RTL_RADIUS|\
     THR_PASS_STAB|THR_SLEWRATE|THR_SUPP_MAN|TKOFF_ACCEL_CNT|\
     TKOFF_THR_.*|TKOFF_ALT|TKOFF_DIST|HOME_RESET_ALT|\
-    ALT_HOLD_RTL|MIN_GNDSPD_CM|ARMING_RUDDER)\$" \
+    ALT_HOLD_RTL|MIN_GNDSPD_CM|ARMING_RUDDER)$" \
     <backup>
 ```
 
@@ -17,6 +17,6 @@ Use it to set up a new plane by copying over settings from an older plane.
 * * *
 
 <p style="font-size:80%; font-style: italic">
-Last updated on June 11, 2022. For any questions/feedback,
+Last updated on August 07, 2022. For any questions/feedback,
 email me at <a href="mailto:hi@stavros.io">hi@stavros.io</a>.
 </p>
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