DIP 74HC165 2ชิ้น

ถ้าขาของ Arduino มีแค่ 3 ขา แล้วอยากรับอินพุต 200 ตัว ซึ่งจะต้องใช้ขา Arduino จำนวน 200 ขา

เพื่อควบคุม แน่นอนว่าขาไม่พอ แล้วจะสั่งควบคุมได้อย่างไร IC ตัวนี้คือคำตอบที่ขอแนะนำ

IC ชิฟรีจิสเตอร์ ใช้ขยายขาอินพุต สามารถต่อพ่วงกันหลาย ๆ ตัวได้ ใช้สัญญาณควบคุมแค่ 3 เส้น ใช้ง่าย

มีโคดสำเร็จรูปให้ใช้งาน

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ตัวอย่างการใช้งาน

ใช้ Resistor 10 k ohm

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 ตัวอย่าง Code

/*

 * SN74HC165N_shift_reg

 *

 * Program to shift in the bit values from a SN74HC165N 8-bit

 * parallel-in/serial-out shift register.

 *

 * This sketch demonstrates reading in 16 digital states from a

 * pair of daisy-chained SN74HC165N shift registers while using

 * only 4 digital pins on the Arduino.

 *

 * You can daisy-chain these chips by connecting the serial-out

 * (Q7 pin) on one shift register to the serial-in (Ds pin) of

 * the other.

 * 

 * Of course you can daisy chain as many as you like while still

 * using only 4 Arduino pins (though you would have to process

 * them 4 at a time into separate unsigned long variables).

 * 

*/

/* How many shift register chips are daisy-chained.

*/

#define NUMBER_OF_SHIFT_CHIPS   1

/* Width of data (how many ext lines).

*/

#define DATA_WIDTH   NUMBER_OF_SHIFT_CHIPS * 8

/* Width of pulse to trigger the shift register to read and latch.

*/

#define PULSE_WIDTH_USEC   5

/* Optional delay between shift register reads.

*/

#define POLL_DELAY_MSEC   500

/* You will need to change the "int" to "long" If the

 * NUMBER_OF_SHIFT_CHIPS is higher than 2.

*/

#define BYTES_VAL_T unsigned int

int ploadPin        = 8;  // Connects to Parallel load pin the 165

int clockEnablePin  = 9;  // Connects to Clock Enable pin the 165

int dataPin         = 11; // Connects to the Q7 pin the 165

int clockPin        = 12; // Connects to the Clock pin the 165

BYTES_VAL_T pinValues;

BYTES_VAL_T oldPinValues;

/* This function is essentially a "shift-in" routine reading the

 * serial Data from the shift register chips and representing

 * the state of those pins in an unsigned integer (or long).

*/

BYTES_VAL_T read_shift_regs()

{

    long bitVal;

    BYTES_VAL_T bytesVal = 0;

    /* Trigger a parallel Load to latch the state of the data lines,

    */

    digitalWrite(clockEnablePin, HIGH);

    digitalWrite(ploadPin, LOW);

    delayMicroseconds(PULSE_WIDTH_USEC);

    digitalWrite(ploadPin, HIGH);

    digitalWrite(clockEnablePin, LOW);

    /* Loop to read each bit value from the serial out line

     * of the SN74HC165N.

    */

    for(int i = 0; i < DATA_WIDTH; i++)

    {

        bitVal = digitalRead(dataPin);

        /* Set the corresponding bit in bytesVal.

        */

        bytesVal |= (bitVal << ((DATA_WIDTH-1) - i));

        /* Pulse the Clock (rising edge shifts the next bit).

        */

        digitalWrite(clockPin, HIGH);

        delayMicroseconds(PULSE_WIDTH_USEC);

        digitalWrite(clockPin, LOW);

    }

    return(bytesVal);

}

/* Dump the list of zones along with their current status.

*/

void display_pin_values()

{

    Serial.print("Pin States:\r\n");

    for(int i = 0; i < DATA_WIDTH; i++)

    {

        Serial.print("  Pin-");

        Serial.print(i);

        Serial.print(": ");

        if((pinValues >> i) & 1)

            Serial.print("HIGH");

        else

            Serial.print("LOW");

        Serial.print("\r\n");

    }

    Serial.print("\r\n");

}

void setup()

{

    Serial.begin(9600);

    /* Initialize our digital pins...

    */

    pinMode(ploadPin, OUTPUT);

    pinMode(clockEnablePin, OUTPUT);

    pinMode(clockPin, OUTPUT);

    pinMode(dataPin, INPUT);

    digitalWrite(clockPin, LOW);

    digitalWrite(ploadPin, HIGH);

    /* Read in and display the pin states at startup.

    */

    pinValues = read_shift_regs();

    display_pin_values();

    oldPinValues = pinValues;

}

void loop()

{

    /* Read the state of all zones.

    */

    pinValues = read_shift_regs();

    /* If there was a chage in state, display which ones changed.

    */

    if(pinValues != oldPinValues)

    {

        Serial.print("*Pin value change detected*\r\n");

        display_pin_values();

        oldPinValues = pinValues;

    }

    delay(POLL_DELAY_MSEC);

}

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ข้อมูลเพิ่มเติม  IC 74hc165 DIP

• https://www.sparkfun.com/products/11512
• http://www.adafruit.com/blog/2011/10/14/part-finder-friday-the-74hc165/
• http://www.gammon.com.au/forum/?id=11979
• http://playground.arduino.cc/Code/ShiftRegSN74HC165N

ตัวอย่างวีดีโอ IC 74hc165 DIP

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