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PlcAux

Auxiliary functions to use with Arduino PLC style

V1.0 ©2023 Juan M. Uribe

Some functions commonly used in PLCs sometimes are needed in the Arduino platform.

Here you can find some of them.

NOTE: this library is already included in the ESPPlcTimer library

USAGE

Add the library "PlcAux.h" in your project. Then you can use the follow functions:

edgeUp //Rising edge detection

bool edgeUp(bool input, bool &prev);

Returns a boolean value that is true one CPU cycle if the input have chanbe from false to true. An auxiliary static bool must to be assigned to prev.

Example:

static bool prev;
if (edgeUp(digitalRead(GPIO_NUM_13), prev)){
    Serial.println("Rising edge detection");
}

edgeDown //Falling edge detection

bool edgeDown(bool input, bool &prev);

Returns a boolean value that is true one CPU cycle if the input have changed form true to false. An auxiliary static bool must to be assigned to prev.

Example:

static bool prev;
if (edgeDown(digitalRead(GPIO_NUM_13), prev)){
  Serial.println("Falling edge detection");
}

changeStatus //change status detection

bool changeStatus(bool input, bool &prev);

Returns a boolean value that is true one CPU cycle if the input have changed. An auxiliary static bool must to be assigned to prev.

Example:

static bool prev;
if (changeStatus(digitalRead(GPIO_NUM_13), prev)){
  Serial.println("Change status detection");
}

sqPulse //Symmetrical pulse

bool sqPulse(uint32_t interval);

Returns a boolean value that is true for half of the specified period and false for the other half.

Example: blinking at 1Hz

digitalWrite(LED_BUILDTIN, sqPulse(1000))

asyncPulse //Asymmetrical pulse

bool asyncPulse(uint32_t tON, uint32_t tOFF);

Returns a boolean value that is true during the TON specified time and false during the TOFF specified time.

Example: asymmetrical blinking of 1Hz, led on 300ms

digitalWrite(LED_BUILDTIN, sqPulse(300, 700))

setBool

void setBool(bool &in);

Set true the boolean value passed at in. The in variable must to be global or have to be declared static bool if local.

resetBool

void resetBool(bool &in);

Set false the boolean value passed at in. The in variable must to be global or have to be declared static bool if local.

Set-Reset flip-flop

bool setReset(bool setIn, bool resetIn, bool &prev);

When the setIn input is true, the output becomes true. When the resetIn input is true, the output becomes false. Reset have priority over set. An auxiliary static bool must to be assigned to prev.

Reset-Set flip-flop

bool ResetSet(bool setIn, bool resetIn, bool &prev);

Works like Set-Reset but here Set have the priority over Reset. An auxiliary static bool must to be assigned to prev.

j-k flip-flop

bool jk(bool jIn, bool kIn, bool ckIn, bool &prev);

When ckIn is false the output is unchanged. if ckIn is true, then works like a set-reset flip-flop: j is set k is reset If j and k are both false the output is unchanged, but if j and k are both true the output changes state.

Example: a push button changes state of an output

void loop() {
  static bool aux, aux2;
  bool input = edgeUp(digitalRead(GPIO_NUM_12), aux);
  digitalWrite(LED_BUILTIN, jk(input, input, true, aux2));
};

t flip-flop

bool t(bool tIn, bool ckIn, bool &prev);

Works like a j-k flip-flop but with only one input assigned to both j and k. When ckIn is false the output is unchanged. If ckIn is true then when t is false the output in unchanged, but if t is true the output changes state. Holding t true and applying a frequency signal to cK we will obtain an output signal of half the frequency. (often used as a frecuency divider by 2)

Example: a push button changes state of an output

void loop() {
  static bool aux, aux2;
  bool input = edgeUp(!digitalRead(GPIO_NUM_12), aux);
  digitalWrite(LED_BUILTIN, t(input, true, aux2));
};