![\"Wemos](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2020\/08\/D1_Mini_Board_beide_Seiten-1024x476.png\")
<\/a>The heart of a Wemos D1 mini board is an ESP8266EX, an ESP8266 12-F or an ESP8285 chip, depending on the version. These are powerful 32-bit microcontrollers with integrated Wi-Fi interface.<\/p>\r\n
So, what the ATmega328P is for the Arduino UNO board, the ESP8266\/ESP8285 is for the Wemos board. And just as the ATmega328P is “stand-alone” programmable (I have reported on it here<\/a>), you can also program the ESP8266\/ESP8285 as such. But for this purpose, you need some additional components such as USB-to-serial adapter. In addition, not for everyone enjoys soldering SMD components like the ESP8266EX. It’s easier to use a development board like the Wemos D1 Mini.<\/p>\r\n\n If you search for the term “D1 Mini”, you will find a bunch of boards with different names. For example, this could be the Lolin D1 Mini, the AZ-Delivery D1 Mini (NodeMCU) shown above, but of course also the Wemos D1 Mini. The “first name” is only a brand or manufacturer name and in my experience does not matter. In the further course of the article I prefer to use the name Wemos D1 Mini, as this is the original. <\/p>\r\n In addition, these boards have different “surnames”, e.g. D1 Mini Pro<\/em>, D1 Mini V3 <\/em>or D1 Mini Lite.<\/em> There are indeed differences here. <\/p>\r\n\n The following technical features are common to all Wemos D1 mini boards:<\/p>\r\n The boards differ mainly in the microcontroller used, the flash memory and the antenna. In addition, there are differences in the USB-to-serial adapter. Some boards use the CH340G, others use the CP2104. This difference is relevant in that different drivers are required. From the name of the board it cannot be concluded with certainty which USB-serial adapter is used. <\/p>\r\n <\/p>\r\n\n The latest representative of the series is the Wemos D1 Mini V4.0.0 (short: D1 Mini V4). The changes compared to the Wemos D1 Mini 3.0.0 (short: D1 Mini V3) are not huge:<\/p>\r\n Normally you will receive pin headers with your board. With AZ-Delivery you will receive various bars (no, I am not paid by them!):<\/p>\r\n\n Personally, I find the socket strips with the long pins handy for experimenting because you can fix the board well on the breadboard and also use the sockets:<\/p>\r\n\n Before you start you have to introduce the Wemos D1 Mini Board to the Arduino IDE. To do this, go to File > Preferences and click on the icon next to “Additional Board Manager URLs”. In the window that pops up, enter the following on a separate line:<\/p>\r\n https:\/\/arduino.esp8266.com\/stable\/package_esp8266com_index.json<\/p>\r\n\n Then you go to Tools – > Board – > Board Manager, search for “esp8266” and install the package:<\/p>\r\n\n Then you restart the Arduino IDE.<\/p>\r\n If your board is detected by Windows, it should appear like this or similar in the Device Manager:<\/p>\r\n\n If your board is not recognized, then you are probably missing the driver for the USB-to-Serial Adapter. The driver for the CH340G can be downloaded here<\/a> or here<\/a> (click on the download icon). Don’t bother with the name “CH341SER”. You can get the driver for the CP2104 here<\/a>.<\/p>\r\n\n Open the Blink Example sketch: File – > Examples – > Basics – > Blink. Then select the correct board in Tools – > Boards:<\/p>\r\n\n Finally, you have to select the right port, and then you are ready to upload the sketch. If all goes well, the on-board LED should flash now:<\/p>\r\n\n With some clones of the Wemos boards, I sometimes had problems uploading programs. In this case, it helped me to press the reset button during compilation and release it when the actual upload is starting.<\/p>\r\n\n I will now go into the most important basic functions, paying particular attention to the differences with the Arduino (Uno).<\/p>\r\n Also on the Wemos D1 Mini Board some pins have multiple functions:<\/p>\r\n\n Some pins have special functions, so there are certain restrictions for them:<\/p>\r\n For the You can use the pins D0 – D8 and RX \/ TX as input or output pins. This means that you have a total of 11 pins at your disposal. To address them, you can use their designation or GPIO number. The following commands have the same effect:<\/p>\r\n For pin D4, it should be noted that it is connected to the board LED. However, in such a way that the board LED lights up when D4 is LOW.<\/p>\r\n The Update: since ESP8266 Arduino Core version 3.0 the default resolution for The Pin A0 is the only analog input. Actually, the analog input of the ESP8266 can only tolerate a maximum of 1 volt. However, on the Wemos D1 mini boards a voltage divider (100 kOhm \/ 220 kOhm) is connected upstream, so that the maximum voltage is 3.2 volts. The resolution is 10 bits. This results in the following for the voltage U:<\/p>\r\n\n <\/p>\r\n <\/span> <\/span> It is interesting that you actually get 1024 for the maximum voltage and not 1023 as with the Arduino UNO. For the latter it’s one of my favorite topics that you have to divide by 1023 and not 1024 when calculating the voltage. So that’s different here.<\/p>\r\n\n I like the function AApart from the general restrictions mentioned above, you can use any pin of the Wemos D1 Mini Board for interrupts. An interrupt is set up as usual via <\/p>\r\n and<\/p>\r\n deactivates it again. For mode, you can choose from:<\/p>\r\n The first three options trigger the interrupt with the signal edge, LOW and HIGH trigger again and again as long as the level of the pin corresponds to the setting.<\/p>\r\n In addition, there are two things to note about the Interrupt Service Routine (ISR):<\/p>\r\n You may also see If you activate I2C with The Wemos D1 Mini boards are capable of the Fast Mode (400 kHz). Beyond that, it gets tight.<\/p>\r\n You have to be careful with the voltage levels of the I2C connection. If you use an I2C component that runs on 5 volts, you need a voltage divider, or you take a logic level converter like this:<\/p>\r\n\n There is not so much to say about SPI. The connections can be found in Table 2.<\/p>\r\n\n You use the pins TX and RX for serial communication like on the Arduino UNO. You can also use pins D7 and D8 (= GPIO 13 \/ RXD2 or GPIO 15 \/ TXD2) instead. All you have to do is insert the instruction Take the following sketch, which is rather pointless in itself, and load it unchanged onto your Wemos D1 Mini Board.<\/p>\r\n In the setup, the board LED flashes ten times at fast frequency. This is simply to visualize the starting point of the sketch. In the main loop, your Wemos D1 Mini Board is waiting for a HIGH signal on D1, e.g. through a button or sensor. If there is no signal, your board should run the <\/p>\r\n\n But if you run the sketch, you will see the flashing LED restarting about every three seconds. Here a security mechanism strikes and this is called watchdog timer. I have reported about watchdog timers in another post<\/a>. The short version is: a watchdog timer is a counter that, if not reset in time, overflows and then triggers a reset. It thus watches over the microcontroller and ensures, for example, that a crashed program is restarted. <\/p>\r\n The Wemos D1 Mini Board, or more precisely the ESP8266, has a software and a hardware watchdog timer. The software watchdog is activated by default and runs over approximately every 3 seconds if it’s not reset. The reset is done by certain functions, e.g. when you restart the main loop, perform a You can extend the time until the reset by turning off the software watchdog. For this purpose, uncomment line 10. However, the hardware watchdog now bites about every 8 seconds. The hardware watchdog cannot be turned off and the watchdog periods cannot be extended further.<\/p>\r\n\n The ESP8266 regularly performs routines that take care of the Wi-Fi function. For example, this happens when the main loop restarts or when a One of the main reasons for choosing a Wemos D1 Mini Board is, of course, its Wi-Fi functionality. Since this a quite extensive topic I have covered it in a separate article<\/a>. As an “appetizer” I would like to show a simple example here. The following sketch allows you to switch an LED connected to D1 via your browser.<\/p>\r\n\n <\/p>\r\n<\/div>\r\n\n Explanations for this sketch and other examples can be found in my article about the ESP8266 ESP-01<\/a>. Or do you want to be informed on your smartphone when certain sensor data exceeds a limit? No problem with IFTTT (if this then that) – I have described this here.<\/a><\/p>\r\n\n Finally, I would like to address the question of how fast the Wemos D1 Mini boards actually are. 80 or 160 MHz sound quite promising compared to the 16 MHz of the Arduino UNO.<\/p>\r\n\n First, I determined the speed of the <\/p>\r\n\n Here are the results for 1 million reads on the Arduino UNO and the D1 Mini at 80 and 160 MHz respectively:<\/p>\r\n In a first rough approximation, this actually corresponds to the ratio of the clock rates.<\/p>\r\n\n For the speed measurement of mathematical operations, I chose By the way, the command Here are the results:<\/p>\r\n In this calculation process the ESP8266 chip is even faster than the ATmega328P as it could be explained by the clock rate. Here, an architectural advantage comes into play. In any case, the difference is really big. But whether you really need it is, of course, a different matter.<\/p>\r\n\n To put the D1 Mini Board into deep sleep and wake it up again, connect the contacts of the SLEEP solder pad. The function ESP.deepSleep(time); sends the board into deep sleep for the period \u201ctime\u201d (in microseconds). Try it with the following sketch:<\/p>\r\n\n A little breather from current sensors:Name confusion<\/h3>\n\n
Key technical features of the Wemos D1 Mini Boards<\/h2>\n\n
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<\/span><\/li>\r\nThe different Wemos D1 Mini Boards<\/h2>\n\n
<\/a><\/a><\/a><\/a><\/a>Wemos D1 Mini V4.0.0 vs. V3.0.0<\/h3>\n\n
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Preparations<\/h2>\n\n
Pin header<\/h3>\n\n
<\/a><\/a><\/figure>\n\nIntegrating the Wemos D1 Mini Board into the Arduino IDE<\/h3>\n\n
<\/a><\/a><\/a>A small test<\/h3>\n\n
<\/a><\/a>Problems using clone boards<\/h2>\n\n
Using the Wemos D1 Board<\/h2>\n\n
<\/a>Restrictions for the use of some pins<\/h4>\n\n
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digitalWrite() \/ analogWrite()<\/h3>\n\n
digitalWrite()<\/code> function, first note that the HIGH signal at the corresponding output is 3.3 volts. The current must not exceed 12 milliamps.<\/p>\r\ndigitalWrite(D2, HIGH);<\/code> \/ digitalWrite(4, HIGH);<\/code><\/p>\r\npinMode<\/code> is set as usual. But there is one particularity. If you want to activate the pull-down resistor of D0 (GPIO 16), then you have to do like this: pinMode(D0, INPUT_PULLDOWN_16)<\/code>.<\/p>\r\nanalogWrite()<\/code> is available for all I\/O pins. This also applies to the pin D0, which has otherwise limited PWM capabilities. In contrast to the Arduino UNO, the resolution is 10 bits. This means that analogWrite(pin, 1023)<\/code> delivers the full voltage.<\/p>\r\nanalogWrite()<\/code> is 8 bit due to compatibility issues. To return to the old behavior, you just have to add analogWriteRange(1023);<\/code> to the setup (see also here<\/a>).<\/p>\r\n\ndigitalRead() \/ analogRead()<\/h3>\n\n
digitalRead()<\/code> works like the Arduino with all pins D0 – D8. The pins RX and TX have their own peculiarities. Therefore, I would not use them for this purpose.<\/p>\r\n<\/p><\/p>\r\n\nanalogRead()<\/code> on the Wemos D1 Mini Boards much more than that on the Arduino UNO. With the Arduino UNO, the analogRead values fluctuate by +\/- two units, even when a stable voltage source is connected. The values determined with the Wemos D1 Mini, on the other hand, do not fluctuate at all.<\/p>\r\n\nInterrupts<\/h3>\n\n
attachInterrupt(digitalPinToInterrupt(Pin), ISR, mode);<\/code><\/p>\r\ndetachInterrupt(digitalPinToInterrupt(Pin));<\/code><\/p>\r\n\r\n
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IRAM_ATTR<\/code> before the function name of the ISR, i.e.: void IRAM_ATTR ISRname() {.....}<\/code>.<\/li>\r\n<\/ol>\r\n\nICACHE_RAM_ATTR<\/code> in older code. It still works, but it is deprecated.<\/p>\r\n\nI2C with the Wemos D1 Mini Board<\/h3>\n\n
Wire.begin()<\/code>, then D1 serves as SCL and D2 as SDA. However, it is not a problem to select other pins according to the scheme Wire.begin(SDA-PIN,SCL-PIN)<\/code>.<\/p>\r\n<\/a>SPI with the Wemos D1 Mini Board<\/h3>\n\n
Serial interface<\/h3>\n\n
Serial.swap()<\/code> after Serial.begin()<\/code> in the setup. <\/p>\r\n\nAttention – biting watchdog<\/h3>\n\n
while()<\/code> loop forever.<\/p>\r\n\nvoid setup() {\r\n pinMode(D1, INPUT); \/\/ Actually redundant, since this state is default\r\n pinMode(LED_BUILTIN, OUTPUT);\r\n for(int i=0; i<10; i++){\r\n digitalWrite(LED_BUILTIN, LOW); \r\n delay(50); \r\n digitalWrite(LED_BUILTIN, HIGH); \r\n delay(50); \r\n }\r\n \/\/ESP.wdtDisable();\r\n}\r\n\r\nvoid loop() {\r\n while(!digitalRead(D1)){\r\n \/\/delay(0); \r\n }\r\n}<\/pre>\r\ndelay()<\/code> or – quite explicitly – by ESP.wdtFeed()<\/code> (the watchdog is fed). Uncomment line 15, and you’ll see that your board isn’t constantly restarting.<\/p>\r\n\nExtending the watchdog period<\/h4>\n\n
What is this is good for?<\/h4>\n\n
delay()<\/code> is executed. If it is not given the opportunity to do so, the ESP8266 prefers to restart to ensure the correct Wi-Fi function. However, this in turn can lead to problems like in the sketch above.<\/p>\r\n\nWi-Fi – Functions<\/h3>\n\n
#include \"ESP8266WebServer.h\"\r\n#define LEDPIN D1\r\n\r\nconst char* ssid = \"Deine SSID\";\r\nconst char* pass = \"Dein Passwort\";\r\nIPAddress ip(192,168,178,xxx); \/\/ xxx = w\u00e4hlt eine frei IP in eurem Heimnetz\r\nIPAddress gateway(192,168,178,1);\r\nIPAddress subnet(255,255,255,0);\r\n\r\nESP8266WebServer server(80);\r\n \r\nString led1= \"<a href=\\\"\/led_an\\\">LED An<\/a>\";\r\nString led0= \"<a href=\\\"\/led_aus\\\">LED Aus<\/a>\";\r\n\r\nvoid handleRoot() {\r\n String message=\"<h1>Testprogramm - Minimalprogramm ESP8266<\/h1>\";\r\n message += \"Hallo ......, das ist ein Gruß vom ESP8266 Server<\/BR><\/BR>\";\r\n message += led1;\r\n server.send(200, \"text\/html\", message);\r\n}\r\n\r\nvoid ledan(){\r\n digitalWrite(LEDPIN, HIGH);\r\n server.send(200, \"text\/html\", led0);\r\n}\r\n\r\nvoid ledaus(){\r\n digitalWrite(LEDPIN, LOW);\r\n server.send(200, \"text\/html\", led1);\r\n}\r\n\r\nvoid setup(){\r\n pinMode(LEDPIN, OUTPUT);\r\n digitalWrite(LEDPIN, LOW);\r\n\/\/ Serial.begin(9600); \r\n\/\/ Serial.println(\"Testprogramm - Minimalprogramm ESP8266\");\r\n\/\/ Serial.print(\"Verbinde mich mit Netz: \");\r\n\/\/ Serial.println(ssid);\r\n WiFi.begin(ssid, pass);\r\n WiFi.config(ip, gateway, subnet); \r\n \r\n\/\/ while(WiFi.status() != WL_CONNECTED){\r\n\/\/ delay(500); Serial.print(\".\");\r\n\/\/ }\r\n\/\/ Serial.println(\"\");\r\n\/\/ Serial.println(\"WiFi Verbindung aufgebaut\");\r\n\/\/ Serial.print(\"Eigene IP des ESP-Modul: \");\r\n\/\/ Serial.println(WiFi.localIP());\r\n\r\n server.on(\"\/\",handleRoot);\r\n server.on(\"\/led_an\", ledan);\r\n server.on(\"\/led_aus\", ledaus);\r\n server.begin();\r\n\/\/ Serial.println(\"HTTP Server wurde gestartet!\");\r\n} \r\n \r\nvoid loop(){\r\n server.handleClient(); \r\n}<\/pre>\r\nSpeed test<\/h2>\n\n
digitalRead();<\/h3>\n\n
digitalRead()<\/code> function. To achieve this, I had the board perform this function a million times. I measured the time required for this by using the millis()<\/code> function.<\/p>\r\n\nvoid setup() {\r\n Serial.begin(9600);\r\n}\r\n\r\nvoid loop() {\r\n long startTime = millis();\r\n for(long i=0; i<1000000; i++){\r\n digitalRead(10);\r\n }\r\n long duration = millis() - startTime;\r\n Serial.println(duration);\r\n}<\/pre>\r\n\r\n
Mathematical operations<\/h3>\n\n
pow(i,0.5)<\/code> which is known to be computationally intensive:<\/p>\r\n\nvoid setup() {\r\n Serial.begin(9600);\r\n}\r\n\r\nvoid loop() {\r\n long startTime = millis();\r\n float f = 0.0;\r\n for(long i=0; i<50000; i++){\r\n f = pow(i,0.5);\r\n }\r\n long duration = millis() - startTime;\r\n Serial.println(duration);\r\n Serial.println(f);\r\n}<\/pre>\r\n\nSerial.println(f)<\/code> is important because the compiler “optimized” the calculation of f by just ignoring it when f is not used. I was very surprised when I always got “0” as a result for “duration” until I noticed that f must be used. <\/p>\r\n\r\n
Deep Sleep<\/h2>\n\n
void setup() {\r\n pinMode(LED_BUILTIN, OUTPUT);\r\n for(int i=0; i<10; i++){\r\n digitalWrite(LED_BUILTIN, HIGH);\r\n delay(50);\r\n digitalWrite(LED_BUILTIN, LOW);\r\n delay(50);\r\n }\r\n ESP.deepSleep(10e6); \/\/ sleep for 10 x 10^6 \u00b5s = 10s\r\n}\r\n\r\nvoid loop() {}<\/pre>\r\n","protected":false},"excerpt":{"rendered":"
\nI present the Wemos D1 Mini Board with its technical features and show how you integrate it into the Arduino IDE. I will highlight the main differences from the Arduino UNO Board. <\/p>\n","protected":false},"author":1,"featured_media":8706,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[543],"tags":[1266,1263,1264,1265,2618,1506,2619,970,1050,1262],"class_list":["post-10729","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-boards-and-microcontrollers","tag-d1-mini-en","tag-d1-mini-lite-en","tag-d1-mini-pro-en","tag-d1-mini-v3-en","tag-d1-mini-v4-en","tag-deep-sleep-en","tag-problems-using-clone-boards","tag-speed","tag-watchdog-en","tag-wemos-d1-mini-en"],"yoast_head":"\n