Arduino Multi-tasking - arduino

Question

I'm trying to see if I can combine tasks that are currently being handled by two separate Arduino Unos onto a single Uno. I was shown the Adafruit guide to "multi-tasking" on the Arduino (Link) and thought I would give it a try.
I feel like I'm missing something really obvious, but my code is just not working...
I'm controlling a series of solenoids. They need to each act based on individual timing. I created a Solenoid class that handles telling the solenoid when to start and then monitor when to close it. For the life of me I can't see where my error is, but I never wind up satisfying my end condition.
class Solenoid {
//Class Variables
int solenoidPin;
long chargeTime;
long ventTime;
bool started = false;
unsigned long startMillis;
unsigned long endMillis;
unsigned long previousMillis;
int solenoidState;
//Constructor
public:
Solenoid(int pin, long charge, long vent) {
solenoidPin = pin;
pinMode(solenoidPin, OUTPUT);
chargeTime = charge;
ventTime = vent;
solenoidState = LOW;
previousMillis = 0;
}
void Start() {
Serial.println("Start called");
started = true;
}
void Update() {
//Check to see if it is time to change the state of the solenoid
unsigned long currentMillis = millis();
Serial.println("Update");
if((started == true) && (currentMillis-previousMillis <= chargeTime)) {
//Run
Serial.print("Run: Charge Time=");
Serial.print(chargeTime);
Serial.print(" current-previous=");
Serial.println(currentMillis-previousMillis);
previousMillis = currentMillis;
} else if ((started == true) && (currentMillis-previousMillis >= chargeTime)){
//Stop
Serial.println("Stop");
}
}
};
//Setup the solenoids
Solenoid solenoid1(13, 70, 70);
void setup() {
Serial.begin(115200);
Serial.println("Ready");
solenoid1.Start();
solenoid1.Update();
solenoid1.Update();
solenoid1.Update();
solenoid1.Update();
solenoid1.Update();
}
I'm just running everything in setup so I can see a few runs.
Can you help me with my clearer stupid mistake?

Answer 1

It's possible that the entire setup() void is executing faster than 70ms, meaning you never get to you end position before the 5 calls to solenoid1.Update() complete.
Try this:
class Solenoid {
//Class Variables
int solenoidPin;
long chargeTime;
long ventTime;
bool started = false;
unsigned long startMillis;
unsigned long endMillis;
unsigned long previousMillis;
int solenoidState;
//Constructor
public:
Solenoid(int pin, long charge, long vent) {
solenoidPin = pin;
pinMode(solenoidPin, OUTPUT);
chargeTime = charge;
ventTime = vent;
solenoidState = LOW;
previousMillis = 0;
}
void Start() {
Serial.println("Start called");
started = true;
}
void Update() {
//Check to see if it is time to change the state of the solenoid
unsigned long currentMillis = millis();
Serial.println("Update");
if((started == true) && (currentMillis-previousMillis <= chargeTime)) {
//Run
Serial.print("Run: Charge Time=");
Serial.print(chargeTime);
Serial.print(" current-previous=");
Serial.println(currentMillis-previousMillis);
previousMillis = currentMillis;
} else if ((started == true) && (currentMillis-previousMillis >= chargeTime)){
//Stop
Serial.println("Stop");
}
}
};
//Setup the solenoids
Solenoid solenoid1(13, 70, 70);
void setup() {
Serial.begin(115200);
Serial.println("Ready");
solenoid1.Start();
}
void loop(){
solenoid1.update()
}
The rest looks fine to me; if you still have issues try using explicit variable declarations instead of your constructor to troubleshoot if that's the issue.

Answer 2

Turns out I was erasing my own counter by setting previousMillis = currentMillis. Once I killed that, it started working. I added some other functionality since then, like a delayed start, but this is primarily the same code.
void Update() {
//Check to see if it is time to change the state of the solenoid
unsigned long currentMillis = millis();
if((started == true) && (currentMillis - startMillis <= startDelay)) {
//keep waiting
Serial.println("Waiting");
} else if((started == true) && (currentMillis - startMillis < (chargeTime + startDelay) )) {
//Run
Serial.print("Run ");
Serial.println(currentMillis - startMillis);
digitalWrite(solenoidPin, HIGH);
} else if ((started == true) && (currentMillis - startMillis >= (chargeTime + startDelay) )){
//Stop
Serial.print("Stop ");
Serial.println(currentMillis - startMillis);
digitalWrite(solenoidPin, LOW);
started = false;
}
}