Refer to the Ultimate Arduino Uno Hardware Manual for the Arduino Uno to find out how analog pins are configured as digital input/output pins, as well as analog input pins. That is because they are multi-function pins. This only works because analog pins can actually be used as digital pins. Some tutorials connect the DATA pin of the DHT11 sensor to an Arduino analog pin such as A0. Arduino Uno DHT11 Temperature Humidity Sensor Circuit Diagram Breadboard layout circuits follow in two subsections for the Uno and MEGA 2560. In fact a value of between 4k7 and 10k works fine for R1. It is intended to be placed close to the sensor power pins to help stabilize the supply voltage. In the circuit diagram, capacitor C1 is an optional capacitor. Use Arduino digital pin 2 in this tutorial, as show in the circuit diagram. Finally connect the DATA or IO pin of the DHT11 to an Arduino digital pin. After that, connect the DHT11 GND pin to Arduino GND. That is, connect the DHT11 VDD or VCC pin to Arduino 5V. Use the same connections on an Arduino MEGA 2560. The following circuit diagram shows how to connect a DHT11 sensor to an Arduino Uno. Arduino DHT11 Sensor Tutorial Circuit Diagram The section after the circuit diagram that follows explains how to install a DHT11 sensor library. In order to use the DHT11 sensor in an Arduino sketch, a DHT11 library is loaded in the Arduino IDE. This is different from the MCP9700 temperature sensor that outputs an analog voltage that represents temperature. That is, it sends serial digital data out on the pin, rather than outputting an analog value. This sensor clocks temperature and humidity data out of the DATA pin. Power the DHT11 sensor with 5V from the Arduino, as explained in the next section. DHT11 Temperature and Humidity Sensor Pinout This allows the sensor to measure the current air temperature and relative humidity. Because of the holes, air passes onto the sensor surface. As can be seen in the image, the sensor has a blue plastic case with square holes. The ATmega2560 however a problem - they ran out of registers in the low I/O space (the bit set clear test instructions only work on the first 32 addresses).The following image shows the DHT11 sensor pin numbering or pinout. If(VPORTB.OUT & 0x01) // 1 word 1 clock for the test, and 1 word for an rjmp (2 if it for some reason needs a jump, but the linker rarely does), just like beforeĤ. VPORTB.OUT |= 3 //3 word, 3 clocks, and not atomic. VPORTB.OUT = 1 // 2 word 2 clock *and not atomic* VPORTB.OUT |= 1 // 1 word and 1 clock (sbi/cbi got faster!) Those are in the low I/O space, and can be accessed like the old PORTx/DDRx/INx registers: The modern AVRs also have "VPORTx.DIR/OUT/IN/INTFLAGS registers.Luckily, DIR and OUT have set/clear/toggle versions - these still take 3 words and 3 clocks to do say, PORTB.OUTCLR = 3 (which would clear the two low bits) but at least it's atomic. These are in extended I/O space, so writes will generally take 2 clocks and reads three, plus the time to prepare the value you want to write (so PORTB.OUT |= 1 would be 5 words and 6 clocks, and is not atomic). On post 2016 AVRs, the register layout is different, PORTB/DDRB/PINB is replaced with PORTB.OUT, PORTB.DIR, PORTB.IN.PORTB |= 0x03 // 3 word, 3 clocks, and not atomic. PORTB = 0x01 // 2 word 2 clocks, *and not atomic* If (PORTB & 0x03) // 2 word 2 clocks for the test then 1 word for a breq/brne - and potentially an extra 1 and 2 ontop of that for an rjmp since conditional branches can only go 64 words in either direction. If(PORTB & 0x01) // 1 word 1 clock for the test, and 1 word for an rjmp (2 if it for some reason needs a jump, but the linker rarely does) - the test instructions are sbic/sbis (Skip if Bit in Io register Clear/Set), that is, they test the bit (taking 1 clock to do so, and depending on the value of the bit either skip (takes 1 clock) or don't skip (takes however long it normally takes) the next instruction, which is almost always a jump of some sort rjmp takes 2 clocks, jmp 3 clocks) Either way, this is atomic, and you don't have to worry about an interrupt firing in the middle PORTB |= 0x01 //1 word, 2 clocks on ATmega2560. PORTx (and DDRx (Data Direction Register) and PIN (PortINput) are "magic" registers because they are located in the "low I/O space", which makes it possible to set, clear, or test them with a single instruction work that executes in 2 clocks on a pre-2016 AVR.Since according to notifications people are still reading this, there are a few things also worth noting: Note that you can also toggle the pin in a single operation by writing a 1 to the PINx register, ex: They typically show the port pin as P, followed by the letter of the port, then the bit within the port (for example PB0 for the pin you referred to). See a pinout chart (google image search will find nice pinout diagrams - just search the board and the word pinout).
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