every five days, reinitialise the clock to fix any eventual drift in the ESP32 real time clock, which isn’t as accurate as the Swiss clocks.<\/li><\/ul>\n\n\n\nThe initials are as always in any Arduino\/ESP32 project, but there are some interesting parts.<\/p>\n\n\n\n
define MAX2719_DIN 27 \/\/ Pins connected to the MAX chip\ndefine MAX2719_CS 25\ndefine MAX2719_CLK 26\ndefine DHTTYPE DHT11 \/\/ DHT 11\ndefine DHTPIN 16 \/\/ Digital pin connected to the DHT sensor\ninclude \"DHT.h\" \/\/ temp and humidity sensor library\ninclude \"WiFi.h\" \/\/ wifi library\ninclude \"time.h\" \/\/ time functions library\nDHT dht(DHTPIN, DHTTYPE);<\/pre>\n\n\n\nThe MAX2719 can be set to listen to almost any pins, but I set them as such in this app. DHTs come in two flavors, DHT11 and DHT16, and as the library can use both, it must be explicitly stated as above. Also, DHTPIN must be selected for use here. WiFi.h and time.h are needed to connect to the WLAN and get the time from the Network Time Server.<\/p>\n\n\n\n
The next bit gets the time structures in place:<\/p>\n\n\n\n
\/\/ time service settings\nconst char* ntpServer = \"pool.ntp.org\"; \/\/ server address\n\/\/ timezone setting. GMT+1 = 3600 GMT+2 = 7200 etc.\nconst long gmtOffset_sec = 7200;\n\/\/ in effect when Daylight Saving Time is in effect\nconst int daylightOffset_sec = 3600;\nstruct tm timeinfo;<\/pre>\n\n\n\nAfter this, you have an object called timeinfo that has the time for further reference. It is loaded using the function goGetTime:<\/p>\n\n\n\n
void goGetTime() {\n\/\/ connect to WiFi\nSerial.printf(\"Connecting to %s \", ssid);\nWiFi.begin(ssid, password);\nwhile (WiFi.status() != WL_CONNECTED) {\ndelay(500);\nSerial.print(\".\");\n}\nSerial.println(\" CONNECTED\");\n\/\/ init and get the time\nconfigTime(gmtOffset_sec, daylightOffset_sec, ntpServer);\nstruct tm timeinfo;\nif (!getLocalTime(&timeinfo)) {\nSerial.println(\"Failed to obtain time\");\nreturn;\n}\n\/\/ disconnect WiFi as it's no longer needed\nWiFi.disconnect(true);\nWiFi.mode(WIFI_OFF);\n}<\/pre>\n\n\n\nSo now you have the function to get the Real Time Clock initialised and running. <\/p>\n\n\n\n
The setup starts the DHT, gets the LEDs initialised and goes to get the time.<\/p>\n\n\n\n
void setup() {\ndht.begin(); \/\/ start the temp-humi sensor\nSerial.begin(115200); \/\/ start serial to device\n\/\/ set pin modes\npinMode(modePinTemp, INPUT_PULLUP);\npinMode(modePinHumi, INPUT_PULLUP);\npinMode(resetButtonPin, INPUT_PULLUP);\npinMode(ledPinHumi, OUTPUT);\npinMode(ledPinTemp, OUTPUT);\npinMode(ledPinDate, OUTPUT);\ninitialise(); \/\/ function for starting LED displays\ngoGetTime(); \/\/ update system time from Network Time\n}<\/pre>\n\n\n\nThen there are a few functions to help figure out what the user wants to see. I have a three way switch rigged in the system, and two pins are connected to the switch. If it is in the up position, you see the date, if down, you see the temperature, and if in the middle and both pins are off, you see the humidity.<\/p>\n\n\n\n
\/\/ function to check if the mode switch is in TEMP setting\nboolean checkModePinTemp() {\nif (digitalRead(modePinTemp) == HIGH) {\nSerial.println(\"Temp mode\");\nreturn true;\n}\nelse {\nreturn false;\n}\n}\n\n\/\/ function to check if the mode switch is in HUMIDITY setting\nboolean checkModePinHumi() {\nif (digitalRead(modePinHumi) == HIGH) {\nSerial.println(\"Humidity mode\");\nreturn true;\n}\nelse {\nreturn false;\n}\n}\n\n\/\/ function to check if the RESET button is pushed\nboolean checkResetButton() {\nif (digitalRead(resetButtonPin) == HIGH) {\nSerial.println(\"Reset request\");\nreturn true;\n}\nelse {\nreturn false;\n}\n}<\/pre>\n\n\n\nThe main loop<\/h3>\n\n\n\n
The main loop is longish, so I’ll just illustrate a few points from it. <\/p>\n\n\n\n
The DHT is read using the following code:<\/p>\n\n\n\n
float h = dht.readHumidity(); \/\/ Read humidity\nString humiStr = String(h);\nfloat t = dht.readTemperature();\/\/ Read temperature as Celsius (the default)\nString tempStr = String(t);\nfloat f = dht.readTemperature(true);\/\/ Read temperature as Fahrenheit (isFahrenheit = true)\n\/\/ error handling routine\nif (isnan(h) || isnan(t) || isnan(f)) {\nSerial.println(F(\"Failed to read from DHT sensor!\"));\ndelay(1000);\nreturn;\n}<\/pre>\n\n\n\nThey are converted into strings, because later on, the numbers must be picked out into tens, ones, decimal tens, and decimal ones, for both the humidity and the temperature displays. For temperature, it looks like this:<\/p>\n\n\n\n
\/\/ this returns the tens of the temperature as Integer\ntempTens = tempStr.substring(0, 1).toInt();\n\/\/ this returns the ones of the temperature as Integer\ntempOnes = tempStr.substring(1, 2).toInt();\n\/\/ this returns the decimal tens of the temperature as Integer\ntempDeciOnes = tempStr.substring(2, 3).toInt();\n\/\/ this returns the decimal ones of the temperature as Integer\ntempDeciTens = tempStr.substring(3, 4).toInt();<\/pre>\n\n\n\nNow I have four integer variables that can be passed to the display unit as single digits. tempTens<\/strong> is picked from the string that contains the temperature with the substring <\/strong>structure. Picking the substring of character 0 to 1 gives you the single digit, but it is in the datatype String. Therefore you need to add the function .toInt()<\/strong> to it, before you pass it on to the LED later on – the digit has to be Integer, not String. <\/p>\n\n\n\nFiguring that out took me a loooong time.<\/p>\n\n\n\n
Before actually lighting up the eight LED digits, I will buffer values into variables once more, to make the actual data passage understandable.<\/p>\n\n\n\n
\/\/ for showing temperature\nif ((boolTempPin == true) && (boolHumiPin == false)) {\n\/\/ if (loopCounter<10) {\nledLeft1 = tempTens;\nledLeft2 = tempOnes + 128; \/\/ +128 gives the decimal point \nledLeft3 = tempDeciTens;\nledLeft4 = tempDeciOnes ;\ndigitalWrite(ledPinTemp, HIGH);\ndigitalWrite(ledPinHumi, LOW);\ndigitalWrite(ledPinDate, LOW);\n}<\/pre>\n\n\n\nHere you also see that I have three LEDs, which indicate the mode of the display. In this IF clause, I pull the ledPinTemp UP HIGH and the others remain LOW. <\/p>\n\n\n\n
If the switch is in the middle position, both pins are LOW and the system is set up to show temperature. And when the switch is in the up position, the ledPinHumi is HIGH, and the system displays the humidity in the left digits.<\/p>\n\n\n\n
The time is always passed to the right side 4 LEDS, hence the time is also parsed into separate digits as thus:<\/p>\n\n\n\n
\/\/ tens digit of day\ndayTens = timeinfo.tm_mday \/ 10;\n\/\/ ones digit of day\ndayOnes = timeinfo.tm_mday % 10;\n\/\/ tens digit of month\nmonthTens = timeinfo.tm_mon \/ 10;\n\/\/ ones digit of month, +1 needed to adjust\nmonthOnes = timeinfo.tm_mon % 10 + 1;\n\/\/ tens digit of hour\nhourTens = timeinfo.tm_hour \/ 10;\n\/\/ ones digit of hour\nhourOnes = timeinfo.tm_hour % 10;\n\/\/ tens digit of minutes\nminuteTens = timeinfo.tm_min \/ 10;\n\/\/ ones digit of minutes\nminuteOnes = timeinfo.tm_min % 10;\n\/\/ set the right LED values for time\n\/\/ ths happens every time, because clock is always on\nledRight1 = hourTens;\nledRight2 = hourOnes + 128;\nledRight3 = minuteTens;\nledRight4 = minuteOnes;<\/pre>\n\n\n\nPushing the digits to the display<\/h3>\n\n\n\n
Once all the data is set in single digit variables, ie. ledLeft1-4 and rightLed1-4, they can be pushed out to be displayed by the dual LED display. This is achieved by using this function:<\/p>\n\n\n\n
void output(byte address, byte data)
{
digitalWrite(MAX2719_CS, LOW);
\/\/ Send out two bytes (16 bit)
\/\/ parameters: shiftOut(dataPin, clockPin, bitOrder, value)
shiftOut(MAX2719_DIN, MAX2719_CLK, MSBFIRST, address);
shiftOut(MAX2719_DIN, MAX2719_CLK, MSBFIRST, data);
digitalWrite(MAX2719_CS, HIGH);
}<\/pre>\n\n\n\n It is given a address as a byte as well as a piece of data as a byte. First the clock pin of the chip is pulled LOW to reset it, then it does two shiftOut operations. Then it is pulled HIGH to display the byte. When this is done eight times, all eight digits are loaded by the shift register, and then displayed at one go.<\/p>\n\n\n\n
\/\/ send all data to LED units\noutput(0x08, ledLeft1); \/\/ Left led 1 value\noutput(0x07, ledLeft2); \/\/ Left led 2 value\noutput(0x06, ledLeft3); \/\/ Left led 3 value\noutput(0x05, ledLeft4); \/\/ Left led 4 value\noutput(0x04, ledRight1); \/\/ Time value in hours, tens\noutput(0x03, ledRight2); \/\/ Time value in hours, ones\noutput(0x02, ledRight3); \/\/ Time value in minutes, tens\noutput(0x01, ledRight4); \/\/ Time value in minutes, ones<\/pre>\n\n\n\nWiring the system<\/h3>\n\n\n\n
I’ll describe the wiring in writing here because this is a rather simple system. Remember to prepare the DHT11 so that you have a 10K resistor between the data lead and the 5V lead – there are still three leads from it, voltage, data, and ground.<\/p>\n\n\n\n
The parts you need are<\/p>\n\n\n\n
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