if you want to remove an article from website contact us from top.

    in arduino ide, pinmode is a built-in function. choose the best one to configure d0 as an output port

    Mohammed

    Guys, does anyone know the answer?

    get in arduino ide, pinmode is a built-in function. choose the best one to configure d0 as an output port from screen.

    Arduino

    Arduino - I/O Functions, The pins on the Arduino board can be configured as either inputs or outputs. We will explain the functioning of the pins in those modes. It is important to note

    Arduino - I/O Functions

    Advertisements Previous Page Next Page

    Arduino Long Distance Communication

    14 Lectures 1 hours Ashraf Said More Detail

    Arduino Wireless Power Transmission

    13 Lectures 50 mins Ashraf Said More Detail

    Arduino Car Parking Assistant

    9 Lectures 42 mins Ashraf Said More Detail

    The pins on the Arduino board can be configured as either inputs or outputs. We will explain the functioning of the pins in those modes. It is important to note that a majority of Arduino analog pins, may be configured, and used, in exactly the same manner as digital pins.

    Pins Configured as INPUT

    Arduino pins are by default configured as inputs, so they do not need to be explicitly declared as inputs with pinMode() when you are using them as inputs. Pins configured this way are said to be in a high-impedance state. Input pins make extremely small demands on the circuit that they are sampling, equivalent to a series resistor of 100 megaohm in front of the pin.

    This means that it takes very little current to switch the input pin from one state to another. This makes the pins useful for such tasks as implementing a capacitive touch sensor or reading an LED as a photodiode.

    Pins configured as pinMode(pin, INPUT) with nothing connected to them, or with wires connected to them that are not connected to other circuits, report seemingly random changes in pin state, picking up electrical noise from the environment, or capacitively coupling the state of a nearby pin.

    Pull-up Resistors

    Pull-up resistors are often useful to steer an input pin to a known state if no input is present. This can be done by adding a pull-up resistor (to +5V), or a pull-down resistor (resistor to ground) on the input. A 10K resistor is a good value for a pull-up or pull-down resistor.

    Using Built-in Pull-up Resistor with Pins Configured as Input

    There are 20,000 pull-up resistors built into the Atmega chip that can be accessed from software. These built-in pull-up resistors are accessed by setting the pinMode() as INPUT_PULLUP. This effectively inverts the behavior of the INPUT mode, where HIGH means the sensor is OFF and LOW means the sensor is ON. The value of this pull-up depends on the microcontroller used. On most AVR-based boards, the value is guaranteed to be between 20kΩ and 50kΩ. On the Arduino Due, it is between 50kΩ and 150kΩ. For the exact value, consult the datasheet of the microcontroller on your board.

    When connecting a sensor to a pin configured with INPUT_PULLUP, the other end should be connected to the ground. In case of a simple switch, this causes the pin to read HIGH when the switch is open and LOW when the switch is pressed. The pull-up resistors provide enough current to light an LED dimly connected to a pin configured as an input. If LEDs in a project seem to be working, but very dimly, this is likely what is going on.

    Same registers (internal chip memory locations) that control whether a pin is HIGH or LOW control the pull-up resistors. Consequently, a pin that is configured to have pull-up resistors turned on when the pin is in INPUTmode, will have the pin configured as HIGH if the pin is then switched to an OUTPUT mode with pinMode(). This works in the other direction as well, and an output pin that is left in a HIGH state will have the pull-up resistor set if switched to an input with pinMode().

    Example

    pinMode(3,INPUT) ; // set pin to input without using built in pull up resistor

    pinMode(5,INPUT_PULLUP) ; // set pin to input using built in pull up resistor

    Pins Configured as OUTPUT

    Pins configured as OUTPUT with pinMode() are said to be in a low-impedance state. This means that they can provide a substantial amount of current to other circuits. Atmega pins can source (provide positive current) or sink (provide negative current) up to 40 mA (milliamps) of current to other devices/circuits. This is enough current to brightly light up an LED (do not forget the series resistor), or run many sensors but not enough current to run relays, solenoids, or motors.

    Attempting to run high current devices from the output pins, can damage or destroy the output transistors in the pin, or damage the entire Atmega chip. Often, this results in a "dead" pin in the microcontroller but the remaining chips still function adequately. For this reason, it is a good idea to connect the OUTPUT pins to other devices through 470Ω or 1k resistors, unless maximum current drawn from the pins is required for a particular application.

    pinMode() Function

    The pinMode() function is used to configure a specific pin to behave either as an input or an output. It is possible to enable the internal pull-up resistors with the mode INPUT_PULLUP. Additionally, the INPUT mode explicitly disables the internal pull-ups.

    pinMode() Function Syntax

    Void setup () {

    pinMode (pin , mode);

    }

    स्रोत : www.tutorialspoint.com

    Digital Pins

    Discover how digital pins work and how they can be configured.

    Digital Pins

    Discover how digital pins work and how they can be configured.

    LAST REVISION:

    11/23/2022, 02:29 PM

    The pins on the Arduino can be configured as either inputs or outputs. This document explains the functioning of the pins in those modes. While the title of this document refers to digital pins, it is important to note that vast majority of Arduino (Atmega) analog pins, may be configured, and used, in exactly the same manner as digital pins.

    Properties of Pins Configured as INPUT

    Arduino (Atmega) pins default to inputs, so they don't need to be explicitly declared as inputs with pinMode() when you're using them as inputs. Pins configured this way are said to be in a high-impedance state. Input pins make extremely small demands on the circuit that they are sampling, equivalent to a series resistor of 100 megohm in front of the pin. This means that it takes very little current to move the input pin from one state to another, and can make the pins useful for such tasks as implementing a capacitive touch sensor, reading an LED as a photodiode, or reading an analog sensor with a scheme such as RCTime.

    This also means however, that pins configured as pinMode(pin, INPUT) with nothing connected to them, or with wires connected to them that are not connected to other circuits, will report seemingly random changes in pin state, picking up electrical noise from the environment, or capacitively coupling the state of a nearby pin.

    Pullup Resistors with pins configured as INPUT

    Often it is useful to steer an input pin to a known state if no input is present. This can be done by adding a pullup resistor (to +5V), or a pulldown resistor (resistor to ground) on the input. A 10K resistor is a good value for a pullup or pulldown resistor.

    Properties of Pins Configured as INPUT_PULLUP

    There are 20K pullup resistors built into the Atmega chip that can be accessed from software. These built-in pullup resistors are accessed by setting the pinMode() as INPUT_PULLUP. This effectively inverts the behavior of the INPUT mode, where HIGH means the sensor is off, and LOW means the sensor is on.

    The value of this pullup depends on the microcontroller used. On most AVR-based boards, the value is guaranteed to be between 20kΩ and 50kΩ. On the Arduino Due, it is between 50kΩ and 150kΩ. For the exact value, consult the datasheet of the microcontroller on your board.

    When connecting a sensor to a pin configured with INPUT_PULLUP, the other end should be connected to ground. In the case of a simple switch, this causes the pin to read HIGH when the switch is open, and LOW when the switch is pressed.

    The pullup resistors provide enough current to dimly light an LED connected to a pin that has been configured as an input. If LEDs in a project seem to be working, but very dimly, this is likely what is going on.

    The pullup resistors are controlled by the same registers (internal chip memory locations) that control whether a pin is HIGH or LOW. Consequently, a pin that is configured to have pullup resistors turned on when the pin is an INPUT, will have the pin configured as HIGH if the pin is then switched to an OUTPUT with pinMode(). This works in the other direction as well, and an output pin that is left in a HIGH state will have the pullup resistors set if switched to an input with pinMode().

    Prior to Arduino 1.0.1, it was possible to configure the internal pull-ups in the following manner:

    1 pinMode(pin, INPUT); // set pin to input

    2 digitalWrite(pin, HIGH); // turn on pullup resistors

    NOTE: Digital pin 13 is harder to use as a digital input than the other digital pins because it has an LED and resistor attached to it that's soldered to the board on most boards. If you enable its internal 20k pull-up resistor, it will hang at around 1.7V instead of the expected 5V because the onboard LED and series resistor pull the voltage level down, meaning it always returns LOW. If you must use pin 13 as a digital input, set its pinMode() to INPUT and use an external pull down resistor.

    Properties of Pins Configured as OUTPUT

    Pins configured as OUTPUT with pinMode() are said to be in a low-impedance state. This means that they can provide a substantial amount of current to other circuits. Atmega pins can source (provide positive current) or sink (provide negative current) up to 40 mA (milliamps) of current to other devices/circuits. This is enough current to brightly light up an LED (don't forget the series resistor), or run many sensors, for example, but not enough current to run most relays, solenoids, or motors.

    Short circuits on Arduino pins, or attempting to run high current devices from them, can damage or destroy the output transistors in the pin, or damage the entire Atmega chip. Often this will result in a "dead" pin in the microcontroller but the remaining chip will still function adequately. For this reason it is a good idea to connect OUTPUT pins to other devices with 470Ω or 1k resistors, unless maximum current draw from the pins is required for a particular application.

    See Also

    pinMode digitalWrite digitalRead

    स्रोत : docs.arduino.cc

    pinMode() function "defaults" to OUTPUT; should be INPUT (IMHO)

    G'day, folks. I was looking over the library source code at how the Arduino digital pin manipulation functions work, and found the pinMode() function definition in the wiring_digital.c file. I am assuming that this is T…

    pinMode() function “defaults” to OUTPUT; should be INPUT (IMHO)

    DevelopmentSuggestions for the Arduino Project

    DuinoSoar Jan '19post #1 G'day, folks.

    I was looking over the library source code at how the Arduino digital pin manipulation functions work, and found the pinMode() function definition in the wiring_digital.c file. I am assuming that this is THE implementation of pinMode. (I used the "Agent Ransack" file search tool, and could not find any other #define or function implementation of pinMode in the source code included with Arduino 1.8.5.) If I am wrong, somebody please feel free to correct me and point out where any different implementation of pinMode would override the one I found in wiring_digital.c.

    Following is the function definition of pinMode(), copied verbatim from wiring_digital.c:

    void pinMode(uint8_t pin, uint8_t mode)

    {

    uint8_t bit = digitalPinToBitMask(pin);

    uint8_t port = digitalPinToPort(pin);

    volatile uint8_t *reg, *out;

    if (port == NOT_A_PIN) return;

    // JWS: can I let the optimizer do this?

    reg = portModeRegister(port);

    out = portOutputRegister(port);

    if (mode == INPUT) {

    uint8_t oldSREG = SREG;

    cli(); *reg &= ~bit; *out &= ~bit; SREG = oldSREG;

    } else if (mode == INPUT_PULLUP) {

    uint8_t oldSREG = SREG;

    cli(); *reg &= ~bit; *out |= bit; SREG = oldSREG; } else {

    uint8_t oldSREG = SREG;

    cli(); *reg |= bit; SREG = oldSREG; } }

    Something bothers me about this implementation: the "default" mode is OUTPUT (i.e. if any value except INPUT or INPUT_PULLUP was passed to the mode parameter).

    This is fine if the sketch author calling pinMode does not make any mistake.

    But suppose the author uses a uint8_t (or byte) variable as the mode argument of the call to pinMode(), in order to dynamically switch modes between, say, INPUT and INPUT_PULLUP (but never intends it to be OUTPUT). Suppose further that this mode variable somehow gets corrupted (e.g. by a bad pointer reference or an array over-run) and is erroneously set to any value other than INPUT or INPUT_PULLUP. Then the mode will "default" to OUTPUT, and possibly damage external circuitry.

    In my opinion (be it ever so humble ), the "default" value, handled by the last "else" clause of the pinMode() function, should be "INPUT" (high-impedance), and the previous, specific conditional clauses (the "if" and "else if" clauses) should specifically handle OUTPUT and INPUT_PULLUP.

    That way, if the passed-in mode argument is "out of range", the pin mode will, at least, "default" to high-impedance input, and would be less likely to cause damage to external circuitry.

    (Note: In the above scenario, there would still, of course, be a 1 in 256 chance that the corrupted mode variable happens to equal the valid OUTPUT value, and still possibly damage external circuitry. But this, I think, would still be much less likely to occur, than if the OUTPUT mode was handled as the "out-of-range" mode default.)

    I would have written the pinMode() function like the following (changed parts shown with original code in red strike-through and new code in green):

    void pinMode(uint8_t pin, uint8_t mode)

    {

    uint8_t bit = digitalPinToBitMask(pin);

    uint8_t port = digitalPinToPort(pin);

    volatile uint8_t *reg, *out;

    if (port == NOT_A_PIN) return;

    // JWS: can I let the optimizer do this?

    reg = portModeRegister(port);

    out = portOutputRegister(port);

    if (mode == [color=red][s]INPUT[/s][/color][color=green]OUTPUT[/color]) {

    uint8_t oldSREG = SREG;

    cli();

    [color=red][s]*reg &= ~bit;[/s][/color]

    [color=red][s]*out &= ~bit;[/s][/color]

    [color=green]*reg |= bit;[/color]

    SREG = oldSREG;

    } else if (mode == INPUT_PULLUP) {

    uint8_t oldSREG = SREG;

    cli(); *reg &= ~bit; *out |= bit; SREG = oldSREG; } else {

    uint8_t oldSREG = SREG;

    cli();

    [color=red][s]*reg |= bit;[/s][/color]

    [color=green]*reg &= ~bit;

    *out &= ~bit;[/color]

    SREG = oldSREG; } }

    Should this be considered for the next release of Arduino software?

    I have another question about pinMode. I understand why the assignments to oldSREG and SREG are placed inside each individual if/else clause, instead of just once before and after all the clauses. (I believe they are inside each clause, in order to keep the length of the critical code down to a minimum, for each case.) But I am wondering (I really do not know) if the compiler builds and tears down the additional byte (for oldSREG) in the stack frame for each clause? Would it be more efficient, in terms of compiled code size, if the declaration:

    uint8_t oldSREG;

    were put at the top of pinMode(), and still keep the individual assignments:

    oldSREG = SREG;

    in each if/else clause just before the cli() calls?

    Thanks and best regards,

    DuinoSoar.

    created

    Jan '19

    last reply

    May '21 5

    replies

    1.8k

    views

    3

    users

    2 2 pert Jan '19post #2 DuinoSoar:

    I am assuming that this is THE implementation of pinMode.

    Only for Arduino AVR Boards. The core for each architecture will have its own definition of pinMode.

    स्रोत : forum.arduino.cc

    Do you want to see answer or more ?
    Mohammed 3 day ago
    4

    Guys, does anyone know the answer?

    Click For Answer