diff --git a/serialservo/serialservo.ino b/serialservo/serialservo.ino
index 3e8306750327cd2eac57c55c84a63b5ab703772c..513d610dd797f4fbeda4c8e8121122f1af11b37c 100644
--- a/serialservo/serialservo.ino
+++ b/serialservo/serialservo.ino
@@ -4,7 +4,7 @@
 // serial servo PWM
 //
 // Neil Gershenfeld 7/28/21
-// Quentin Bolsee 7/12/2021 : add button
+// Quentin Bolsee 12/7/21 : add button
 //
 // This work may be reproduced, modified, distributed,
 // performed, and displayed for any purpose, but must
@@ -34,6 +34,7 @@ void loop() {
    if (SerialUSB.available()) {
       SerialUSB.readBytes((char *)&duration,2);
       if (duration == 65535L) {
+         // special command, reply with button value
          int btn = digitalRead(BUTTON);
          SerialUSB.write(btn ? '1' : '0');
          }
diff --git a/serialstep/serialstep.ino b/serialstep/serialstep.ino
index e0befc187c1d048d54ca8e0122f856302e33dba0..7fc05f7ecf1741e50bb02c8ae613f8da2f95731c 100644
--- a/serialstep/serialstep.ino
+++ b/serialstep/serialstep.ino
@@ -4,7 +4,7 @@
 // serial step-and-direction
 //
 // Neil Gershenfeld 4/11/21
-// Quentin Bolsee 7/12/2021 : add button
+// Quentin Bolsee 12/7/21 : add button
 //
 // This work may be reproduced, modified, distributed,
 // performed, and displayed for any purpose, but must
@@ -62,7 +62,7 @@ void setup() {
    */
    // 1/32 step
    digitalWrite(M0,LOW);
-   pinMode(M0,OUTPUT);   
+   pinMode(M0,OUTPUT);
    pinMode(M1,INPUT);
    }
 
@@ -82,6 +82,7 @@ void loop() {
          digitalWrite(STEP,LOW);
          }
       else if (c == '?') {
+         // reply with button value
          int btn = digitalRead(BUTTON);
          SerialUSB.write(btn ? '1' : '0');
          }