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--- en:pfw:dht22 [2025-04-25 01:13] – [Source Code] mka
+++ en:pfw:dht22 [2025-06-27 12:05] (current) – [Implementation for RP2040 using a PIO block] mka
@@ Line 1: / Line 1: @@
 {{pfw:full-banner.png?500 }}
-====== DHT22 Protocol ======
+====== DHT22 ======
-===== Introduction =====
 The DHT22 module is a low-cost digital temperature and humidity sensor. It utilizes a capacitive humidity sensor and a thermistor to measure the surrounding air and outputs a digital signal via a single data pin. It's known for its wider measurement range and higher accuracy compared to its predecessor, the DHT11.
@@ Line 16: / Line 14: @@
 * Suitable for indoor environmental monitoring, weather stations, and HVAC systems.
-===== SDA =====
+===== SDA Protocol =====
 The DHT22 communicates using a **proprietary single-wire serial protocol**. Here's a breakdown of the process:
@@ Line 37: / Line 35: @@
 The microcontroller needs to carefully time these pulses to correctly interpret the data sent by the DHT22. Libraries for popular platforms like Arduino and Raspberry Pi handle these timing-critical operations.
 [[https://wiki.forth-ev.de/lib/exe/fetch.php/pfw:am2302-en-aosong.pdf|am2302-en-aosong.pdf]] This Aosong document has the correct data, although it is a creepy English translation.
+On page 2, under 4, "The definition of single-bus interface," pin 2 of the sensor is called **SDA, Serial Data**. A table and a figure show the pin assignment of the AM2302.
 {{ :en:pfw:dht22-response.png?nolink |Screenshot of the 40-bit response on the SDA line. (PulsView Logic Analyser)}}
-===== Implementation =====
-==== Testing with a Logic Analyser (PulsView) ====
+===== Testing with a Logic Analyser (PulsView) =====
 Pin P1.0 is bidirectional. It sends the start pulse and then receives the 40 data bits from the sensor module.
@@ Line 56: / Line 56: @@
 {{ :en:pfw:dht22-bit_lesen_mit_2xmoon.png?nolink |The timing is critical. So, it's correct now. Here we read a "0"}}
-==== Pseudocode ====
+====== Implementation for TI's Launchpad ======
-<code>
+This program was used to test DHT22 modules before installation. The DHT22 modules were tested for functionality at room temperature, pre-sorted in this way, and then frozen in a bag of moist sand in the freezer and tested again. One module displayed incorrect temperature values in frost conditions, the display of negative values did not comply with the specifications.
-Function: Pio    ( -- )  \ set port I/O function. SDA --> P1.0
-Function: wakeup ( -- )  \ notify sensor to prepare the data
-Function: @data  ( -- sun moon hum tmp chk chksum )  \ get sensor data
-  get response time of sensor, store in register 'sun' (just for testing)
-  get startpulse duration, store in register 'moon'
-loop
-     read bit using 'moon' based delay
-     lshift bit into array xx yy zz
-loop
-     lshift array  \ adjust xx yy zz --> hum tmp chk
-  calculate chksum
-Function: (dht22)  ( -- sun moon hum tmp chk chksum ) \ wake up and read sensor
-Function:  dht22   ( -- )  \ print temperatur and humidity
-Function:  test    ( n -- ) \ multiple readings
-    n loop  dht22
-</code>
-==== Source Code ====
+[[en:pfw:dht22-msp430g2553-noforth|DHT22 for Launchpad MSP430G2553 and noForth]]
-[[en:pfw:dht22-msp430g2553-noforth|DHT22 with Launchpad MSP430G2553]]
+====== Implementation for RP2040 ======
-==== More information on the MSP430G2553 ====
+[[en:pfw:dht22-rp2040-nofortht|DHT22 for the Raspberry Pi Pico Board RP2040 and noForth t]] using a PIO block
+PIO stands for //Programmable Input Output//. You can program the PIO blocks with the [[en:pfw:assemblers_pio-assembler|noforth t PIO Assembler]].
+====== Background Information ======
+  * How this was discovered: [[en:pfw:dht22tmpformat|The temperature format of the DHT22]]
   * [[https://www.ti.com/lit/ug/slau144j/slau144j.pdf|MSP430x2xx Family guide SLAU144J.PDF]]
   * [[https://www.ti.com/lit/ds/symlink/msp430g2553.pdf|MSP430G2553 datasheet SLAS735J.PDF]], port data on page 49ff
+  * [[https://home.hccnet.nl/anij/nof/noforth.html| noforth.html - find your version, docmentation,  tool.f and asm.f here.]] All about noForth.
+  * [[en:pfw:whatisapioblock|What is a PIO block?]]
----
+====== Aids ======
-=== Source code editor ===
+MK:\\
 I like //Notepad Next// for Linux, a cross-platform, reimplementation of //Notepad++//.
-https://github.com/dail8859/NotepadNext
+https://github.com/dail8859/NotepadNext\\
-=== Terminal ===
 To work with the embedded noForth system I use //e4thcom// by Manfred Mahlow.
-https://wiki.forth-ev.de/doku.php/projects:e4thcom
+https://wiki.forth-ev.de/doku.php/projects:e4thcom\\
+Sometimes I also use Windows and Teraterm, for example, to log longer MCU outputs to a file. I also prefer it for testing parts of the source code using copy and paste.\\
-=== Logic Analyser ===
+In this project I used a Logic Analyzer by AZDelivery, 8 CH, 24MHz. (Amazon)\\
-AZDelivery Logic Analyzer 8 CH, 24MHz. (Amazon)
 //PulseView// is a Qt-based logic analyzer and oscilloscope GUI for sigrok.
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