diff --git a/CHANGELOG.md b/CHANGELOG.md
index 71e6913..28c09b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.4.21] - 2024-10-09
+- add dhtnew_pulse_diag_ext.ino for extended diagnosis.
+
 ## [0.4.20] - 2024-03-24
 - fix #95, units of T & H
 - update GitHub actions
@@ -14,7 +17,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - update unit test (minor)
 - minor edits
 
-
 ## [0.4.19] - 2023-10-25
 - update readme.md
 
diff --git a/README.md b/README.md
index ec3b727..9f08458 100644
--- a/README.md
+++ b/README.md
@@ -25,8 +25,11 @@ Note there are differences e.g. DHT11 has no negative temperature, no decimals,
 The DHTNew library returns Temperature in degrees Celsius and Humidity in 0.0 - 100.0 %RH.
 For converting temperature to Fahrenheit or Kelvin, see https://github.com/RobTillaart/Temperature.
 
+For diagnosis if a DHT sensor gives strange readings one can use **dhtnew_pulse_diag_ext.ino**
+to compare timing with the datasheet.
 
-#### Sonoff Si7021
+
+### Sonoff Si7021
 
 Since 0.4.14 there is **experimental** support for the Sonoff Si7021. 
 No hardware yet to test this myself, but it is confirmed to work.
@@ -39,7 +42,7 @@ To use the library one should call **setType(70)**.
 Feedback (both positive and negative) about the Sonoff Si7021 sensors is welcome.
 
 
-#### AM2320, AM2321 and AM2322
+### AM2320, AM2321 and AM2322
 
 Since 0.4.18 there is **experimental** support for the AM2320, AM2321 and AM2322.
 Not tested myself, but AM2320 is confirmed to work, see https://github.com/RobTillaart/AM232X/issues/26
@@ -54,7 +57,7 @@ Feedback (both positive and negative) about the AM232X sensors is welcome.
 **Note: check the datasheet how to connect!**
 
 
-#### Related
+### Related
 
 - https://github.com/RobTillaart/DHTNew
 - https://github.com/RobTillaart/DHTStable
@@ -174,7 +177,7 @@ This is used to keep spikes out of your plotter / graphs / logs.
 See examples
 
 
-#### TIME_OUT
+### TIME_OUT
 
 If consistent TIMOUT_C or TIMEOUT_D occur during reading a sensor, 
 one could try if allowing interrupts solves the issue **DHT.setDisableIRQ(false)**.
@@ -188,7 +191,7 @@ In version 0.4.10 the TIMEOUT_C is extended from 70-90 us to even suppress the T
 even more. See discussion and tests in https://github.com/RobTillaart/DHTNew/issues/67.
 
 
-#### Serial
+### Serial
 
 The MKR1010Wifi board need to wait for Serial at startup if you want to monitor it 
 from the IDE. Adding the line ```while(!Serial):``` fixes this. (added to the examples).
@@ -196,14 +199,14 @@ from the IDE. Adding the line ```while(!Serial):``` fixes this. (added to the ex
 There might be more boards that need this line to work properly.
 
 
-#### DHT22 and ESP8266
+### DHT22 and ESP8266
 
 - The DHT22 sensor has some problems in combination with specific pins of the ESP8266. See more details
   - https://github.com/RobTillaart/DHTNew/issues/31  (message Jan 3, 2021)
   - https://github.com/arendst/Tasmota/issues/3522
 
 
-#### Voltage AM2301 and ESP8266
+### Voltage AM2301 and ESP8266
 
 In a test an AM2301 had problems giving no humidity (99.9% overflow) when the
 DHTStable library was used with an ESP8266. (Reported by mail, no GH issue).
@@ -313,10 +316,12 @@ Fix #84 correct the reading of type 70 for Sonoff Si7021.
 fix #86, define constants explicit as float.
 34. (0.4.18)
 Update readme.md and library.\* about support for AM2320/21/22.
-35. (0.4.19) 
+35. (0.4.19)
 Update readme.md
-36. (0.4.20) 
+36. (0.4.20)
 Update GitHub actions and readme.md
+36. (0.4.21)
+Add dhtnew_pulse_diag_ext.ino
 
 
 ## Future
diff --git a/dhtnew.cpp b/dhtnew.cpp
index 96d19a4..b97fed6 100644
--- a/dhtnew.cpp
+++ b/dhtnew.cpp
@@ -1,7 +1,7 @@
 //
 //    FILE: dhtnew.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.20
+// VERSION: 0.4.21
 // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
 //     URL: https://github.com/RobTillaart/DHTNEW
 //
diff --git a/dhtnew.h b/dhtnew.h
index 5d50dd5..f57dcf4 100644
--- a/dhtnew.h
+++ b/dhtnew.h
@@ -2,7 +2,7 @@
 //
 //    FILE: dhtnew.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.20
+// VERSION: 0.4.21
 // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
 //     URL: https://github.com/RobTillaart/DHTNEW
 //
@@ -18,7 +18,7 @@
 #include "Arduino.h"
 
 
-#define DHTNEW_LIB_VERSION                (F("0.4.20"))
+#define DHTNEW_LIB_VERSION                (F("0.4.21"))
 
 
 #define DHTLIB_OK                         0
diff --git a/examples/dhtnew_pulse_diag_ext/dhtnew_pulse_diag_ext.ino b/examples/dhtnew_pulse_diag_ext/dhtnew_pulse_diag_ext.ino
new file mode 100644
index 0000000..a6c2f65
--- /dev/null
+++ b/examples/dhtnew_pulse_diag_ext/dhtnew_pulse_diag_ext.ino
@@ -0,0 +1,262 @@
+//
+//    FILE: dhtnew_pulse_diag_ext.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: DHTNEW library pulse measurement tool - diagnostics
+//     URL: https://github.com/RobTillaart/DHTNew
+
+//  DHT PIN layout from left to right
+//  =================================
+//  FRONT : DESCRIPTION
+//  pin 1 : VCC
+//  pin 2 : DATA
+//  pin 3 : Not Connected
+//  pin 4 : GND
+
+
+#include "Arduino.h"
+
+#define DHTLIB_DHT11_WAKEUP        18
+#define DHTLIB_DHT_WAKEUP          1
+
+#define BIT_THRESHOLD              50
+
+
+uint8_t   _dataPin = 5;
+uint8_t   _wakeupDelay = DHTLIB_DHT_WAKEUP;
+
+uint16_t  count = 0;
+uint32_t  times[100], t = 0;
+uint8_t   idx = 0;
+uint32_t  value;
+
+void setup()
+{
+  while (!Serial);       //  MKR1010 needs this
+
+  Serial.begin(115200);
+  Serial.println("dhtnew_pulse_diag_ext.ino");
+  Serial.println();
+
+  //  default should be HIGH
+  pinMode(_dataPin, OUTPUT);
+  digitalWrite(_dataPin, HIGH);
+}
+
+
+void loop()
+{
+  measure();
+  dump();
+  delay(5000);
+}
+
+
+void dump()
+{
+  int i = 1;
+  Serial.println();
+  Serial.print("RUN:\t"); Serial.println(count);
+  Serial.print("IDX:\t"); Serial.println(idx);
+
+  Serial.println("WAKEUP");
+  for (int n = 0; n < 6; n++)
+  {
+    Serial.print("\t");
+    Serial.print(times[i++]);
+  }
+  Serial.println();
+
+  Serial.println("HUM");
+  uint16_t raw_humidity = 0;
+  for (int n = 0; n < 32; n++)
+  {
+    Serial.print("\t");
+    if (n % 2)
+    {
+      raw_humidity <<= 1;
+      if (times[i] > BIT_THRESHOLD) raw_humidity |= 1;
+    }
+    Serial.print(times[i++]);
+    if ((n & 15) == 15) Serial.println();
+  }
+  Serial.print("RAW H:\t0b");
+  Serial.print(raw_humidity, BIN);
+  Serial.print(" = 0x");
+  Serial.print(raw_humidity, HEX);
+  Serial.print(" = ");
+  Serial.print(raw_humidity, DEC);
+  Serial.print(" = ");
+  Serial.print(raw_humidity * 0.1, 1);
+  Serial.print("%");
+  Serial.println();
+  Serial.println();
+
+  Serial.println("TEMP");
+  uint16_t raw_temperature = 0;
+  for (int n = 0; n < 32; n++)
+  {
+    Serial.print("\t");
+    if (n % 2)
+    {
+      raw_temperature <<= 1;
+      if (times[i] > BIT_THRESHOLD) raw_temperature |= 1;
+    }
+    Serial.print(times[i++]);
+    if ((n & 15) == 15) Serial.println();
+  }
+  Serial.print("RAW T:\t0b");
+  Serial.print(raw_temperature, BIN);
+  Serial.print(" = 0x");
+  Serial.print(raw_temperature, HEX);
+  Serial.print(" = ");
+  Serial.print(raw_temperature, DEC);
+  Serial.print(" = ");
+  Serial.print(raw_temperature * 0.1, 1);
+  Serial.print("C");
+  Serial.println();
+  Serial.println();
+
+  Serial.println("CRC");
+  uint8_t raw_CRC = 0;
+  for (int n = 0; n < 16; n++)
+  {
+    Serial.print("\t");
+    if (n % 2)
+    {
+      raw_CRC <<= 1;
+      if (times[i] > BIT_THRESHOLD) raw_CRC |= 1;
+    }
+    Serial.print(times[i++]);
+    if ((n & 7) == 7) Serial.println();
+  }
+  Serial.print("CRC:\t0b");
+  Serial.print(raw_CRC, BIN);
+  Serial.print(" = ");
+  Serial.print(raw_CRC, DEC);
+  Serial.print(" <=> ");
+  uint8_t calc_crc = 0;
+  calc_crc += (raw_humidity >> 8) + (raw_humidity & 0xFF);
+  calc_crc += (raw_temperature >> 8) + (raw_temperature & 0xFF);
+  Serial.print(calc_crc, DEC);
+  Serial.println();
+  Serial.println();
+  Serial.println();
+
+  Serial.println("BYE");
+  for (int n = 0; n < 2; n++)
+  {
+    Serial.print("\t");
+    Serial.print(times[i++]);
+  }
+  Serial.println();
+  Serial.println();
+}
+
+
+void measure()
+{
+  Serial.print(F("\n===================================\n"));
+
+  count++;
+  //  yield(); // handle pending interrupts
+
+  //  reset measurements table
+  idx = 0;
+  t = micros();
+  for (int i = 0; i < 100; i++) times[i] = 0;
+
+  times[idx++] = micros();
+  //  REQUEST SAMPLE - SEND WAKEUP TO SENSOR
+  pinMode(_dataPin, OUTPUT);
+  digitalWrite(_dataPin, LOW);
+  //  add 10% extra for timing inaccuracies in sensor.
+  delayMicroseconds(_wakeupDelay * 1100UL);
+
+  Serial.print("awake ");
+
+  times[idx++] = micros();
+  //  HOST GIVES CONTROL TO SENSOR
+  pinMode(_dataPin, INPUT_PULLUP);
+
+  //  DISABLE INTERRUPTS when clock in the bits
+  //  noInterrupts();      // gives problems on AVR
+
+
+  times[idx++] = micros();
+  //  SENSOR PULLS LOW after 20-40 us  => if stays HIGH ==> device not ready
+  while (digitalRead(_dataPin) == HIGH);
+
+  Serial.print("2 ");
+
+  times[idx++] = micros();
+  //  SENSOR STAYS LOW for ~80 us => or TIMEOUT
+  while (digitalRead(_dataPin) == LOW);
+
+  Serial.print("3 ");
+
+
+  times[idx++] = micros();
+  //  SENSOR STAYS HIGH for ~80 us => or TIMEOUT
+  while (digitalRead(_dataPin) == HIGH);
+  times[idx++] = micros();
+
+  Serial.print("4 ");
+
+
+  //  SENSOR HAS NOW SEND ACKNOWLEDGE ON WAKEUP
+  //  NOW IT SENDS THE BITS
+
+  //  READ THE OUTPUT - 40 BITS => 5 BYTES
+  uint32_t start = micros();
+  uint8_t i = 40;
+  for (i = 40; i != 0; i--)
+  {
+    times[idx++] = micros();
+    //  EACH BIT START WITH ~50 us LOW
+    while (digitalRead(_dataPin) == LOW)
+    {
+      if (micros() - start > 10000)
+      {
+        Serial.print(" <");
+        Serial.println(i);
+        Serial.println("> ");
+        break;
+      }
+    }
+
+    times[idx++] = micros();
+    //  DURATION OF HIGH DETERMINES 0 or 1
+    //  26-28 us ==> 0
+    //     70 us ==> 1
+    while (digitalRead(_dataPin) == HIGH)
+    {
+      if (micros() - start > 10000)
+      {
+        Serial.println(i);
+        break;
+      }
+    }
+  }
+
+  Serial.print("5 ");
+
+  times[idx++] = micros();
+  //  After 40 bits the sensor pulls the line LOW for 50 us
+  //  TODO: should we wait?
+  while (digitalRead(_dataPin) == LOW);
+
+  Serial.print("6 ");
+
+  times[idx++] = micros();
+  times[idx++] = micros();
+
+  for (int n = 100; n > 0; n--)
+  {
+    times[n] -= times[n - 1];
+  }
+
+  Serial.println("7 ");
+}
+
+
+//  -- END OF FILE --
diff --git a/examples/dhtnew_pulse_diag_ext/example_DHT22.txt b/examples/dhtnew_pulse_diag_ext/example_DHT22.txt
new file mode 100644
index 0000000..0854ab8
--- /dev/null
+++ b/examples/dhtnew_pulse_diag_ext/example_DHT22.txt
@@ -0,0 +1,69 @@
+dhtnew_pulse_diag_ext.ino
+
+
+===================================
+awake 2 3 4 14
+13
+12
+11
+10
+9
+8
+7
+6
+5
+4
+3
+2
+1
+5 6 7 
+
+RUN:	1
+IDX:	89
+WAKEUP
+	1280	8	76	56	60	24
+HUM
+	20	80	52	76	64	24	52	36	44	36	44	28	52	28	52	28
+	52	24	52	28	72	64	72	16	56	68	52	80	52	68	52	80
+RAW H:	0b1100000000101111 = 0xC02F = 49199 = 4919.9%
+
+TEMP
+	52	28	52	72	60	28	52	76	52	80	52	68	52	80	52	72
+	52	68	64	16	52	7340	8	152	12	144	12	136	12	144	12	92
+RAW T:	0b101111110111111 = 0x5FBF = 24511 = 2451.1C
+
+CRC
+	20	92	12	92	12	92	12	100
+	16	96	8	96	8	96	8	124
+CRC:	0b11111111 = 255 <=> 13
+
+
+BYE
+	28	4
+
+
+===================================
+awake 2 3 4 5 6 7 
+
+RUN:	2
+IDX:	89
+WAKEUP
+	1296	12	44	76	60	24
+HUM
+	36	20	68	20	52	24	56	24	52	28	52	36	44	76	52	28
+	60	80	52	24	56	68	52	88	44	72	52	88	44	68	60	16
+RAW H:	0b1010111110 = 0x2BE = 702 = 70.2%
+
+TEMP
+	72	24	52	28	52	28	60	20	60	20	52	24	56	24	56	24
+	72	72	52	28	52	76	52	72	52	72	52	80	56	68	56	24
+RAW T:	0b10111110 = 0xBE = 190 = 19.0C
+
+CRC
+	64	28	52	68	64	72	52	68
+	52	80	52	72	52	72	52	44
+CRC:	0b1111110 = 126 <=> 126
+
+
+BYE
+	52	4
diff --git a/library.json b/library.json
index 1445a46..878b32b 100644
--- a/library.json
+++ b/library.json
@@ -13,7 +13,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/DHTNEW.git"
   },
-  "version": "0.4.20",
+  "version": "0.4.21",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*",
diff --git a/library.properties b/library.properties
index 66d3ec8..02fdeab 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=DHTNEW
-version=0.4.20
+version=0.4.21
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for DHT temperature and humidity sensor, with automatic sensortype recognition.