gpio-webhook-arduino/gpio-webhook-arduino.ino

#include "config.h"
#include "wifi.h"
#include <ArduinoJson.h>

// how long to delay between each request to the
// server, in ms.
const int REQUEST_RATE = 1500;

// how long to keep a momentary switch high.
// results approximate, and must be shorter than REQUEST_RATE.
const int MOMENTARY_PERIOD = 250;

// Custom pin status for momentary switch that shouldn't
// get toggled again yet.
const int OLD_HIGH = 255;

// Holds the current state of all the pins.
// Gets written to by parse_webhook_response().
// Gets read from by set_pins().
int pin_states[NUM_PINS] = {0};

// if any momentary pins went high this loop, we
// wait the agreed upon delay and then turn them off.
// if any momentary data input went low, we "reset"
// the pin.
//
// returns the time spent delaying, if any.
int handle_momentary() {
  bool need_delay = false;
  for (int i = 0; i < NUM_PINS; i++) {
    // if [the pin is momentary] and [it was set high this cycle]
    if (PIN_MAP[i][1] == 0 && pin_states[i] == HIGH) {
      need_delay = true;
      break;
    }
  }

  if (!need_delay) {
    return 0;
  }

  delay(MOMENTARY_PERIOD);

  for (int i = 0; i < NUM_PINS; i++) {
    // if [the pin is momentary] and [it was set high this cycle]
    if (PIN_MAP[i][1] == 0 && pin_states[i] == HIGH) {
      // set the pin back to low and make it 'sticky' until we read a low again.
      digitalWrite(PIN_MAP[i][0], LOW);
      pin_states[i] = OLD_HIGH;
    }
  }

  return MOMENTARY_PERIOD;
}

// poll_server makes the actual HTTP request and handles
// the result. It returns false if an error occurred.
bool poll_server() {
  String data = FetchURL(WEBHOOK_URL);
  if (data == "") return false;
  parse_webhook_response(data);
  return true;
}

void parse_webhook_response(String raw_data) {
  StaticJsonDocument<256> doc;
  DeserializationError err = deserializeJson(doc, raw_data);

  if (err) {
    Serial.print("Couldn't parse json data. Error code: ");
    Serial.println(err.c_str());
  }

  JsonArray data = doc.as<JsonArray>();
  int i = 0;
  for (JsonVariant item : data) {
    if (tripped(i) && data[i] == HIGH) {
      continue;
    }

    pin_states[i] = item;
    i++;
  }

  if (data.size() < NUM_PINS) {
    Serial.println("Did not receive data for all pins.");
  }
}

// Set the pins to the right state, and set them all to high during
// initialization.
void initPins() {
  for (int i = 0; i < NUM_PINS; i++) {
    pinMode(PIN_MAP[i][0], OUTPUT);
    digitalWrite(PIN_MAP[i][0], HIGH);
  }

}

// Uses the current pin_states to actually write to the pins
void writePins() {
  for (int i = 0; i < NUM_PINS; i++) {
    if (tripped(i)) {
      continue;
    }

    digitalWrite(PIN_MAP[i][0], pin_states[i]);
  }
}

// returns true if pin at map index i (not pinout numbering) is momentary
// and has been tripped (received a 1 without a subsequent 0 yet)
// returns false otherwise
bool tripped(int i) {
  return PIN_MAP[i][1] == 0 && pin_states[i] == OLD_HIGH;
}

void setup() {
  Serial.begin(9600);
  initPins();
  InitWifi();
}

void loop() {
  poll_server();
  writePins();
  int elapsed = handle_momentary();

  Serial.flush();
  delay(REQUEST_RATE - elapsed);
}