Simple LED Sequence with Button Question..

Question

Hello all..

I want to make a simple 3 LED Sequence circuit and would like some assistance as to where to get started. Basically, press a push button, have LED1 Light, press it again, LED2 Light, Press again LED3 on, Press again back to LED1.Etc... I just can't get it in my head to to what code to use. Thank you for any assistance.

mcb1 · Accepted Answer

George Well done on exploring the possibilities of microcontrollers. Yes you could do this with hardware, but the idea was to do first steps and learn, then progress to more complicated that cannot be done easily with hardware. I see you have used the Debounce example in the Arduino IDE. It works but IMO is wasteful because it constantly writes the LED output, and constantly resets the lastButtonState. (note ... they change lastButtonState constantly) Your problem starts in line 54. You read the input and compare it to lastButtonState. This never changes, so as soon as the button is HIGH line 54 equates to TRUE. You reset the timer, BUT in line 59 you are checking 'are we there yet'. Line 59 will equate to FALSE, and you return to the loop. You then read the button and again reset the timer ... etc. If you add this lastButtonState = digRead1; if (buttonState == 1)
 {
 changeState();
 }
 }
 }
 lastButtonState = digRead1;
 } at Line 75 and shift the } down one more line it should work. One alternative is this approach void Check_Buttons()

/* This routine checks the timer (LastButtonCheck) and if necessary reads the button input
 If the button is detected, it waits until it counts it 10 times at the set time rate.
 This prevents button bounce from triggering and ensures the button is pressed.
 
 Once a valid button press has been detected, it starts a timer (ButtonPressTime),
 
 */ 
 {
 if (millis() - LastButtonCheck > 5) // Reads button state every 5mS and then updates button counts
 { 
 ButtonState = digitalRead(Pushbutton);
 LastButtonCheck = millis();
 
 if (ButtonState == HIGH)
 {
 ButtonCount ++; // Increment the Count by 1
 if (ButtonCount > 5) // the button should be HIGH for 5x5mS = 25mS
 {
 // Button has been pressed for longer than 25mS so its valid
 ButtonPressTime = millis(); // set the Button press timer
 ButtonCount = 0;
 ProcessButton(); // Do something with the valid button press
 }
 }
 else // Button is LOW
 {
 ButtonCount =0; // Reset the counter as the button has been released
 }
 }
 } While it checks the button every xx it doesn't do anything unless its in that state for 5 times x. They do something similar here http://playground.arduino.cc/Learning/SoftwareDebounce Your reset of fsm also needs a tweak. You reset the counter to zero in line 107 and you have no case for zero. It therefore takes two button presses after the third LED is light. It's a simple fix fsm =1; Keep it up its the best way to learn. BTW I always comment at the start about how the inputs are connected, since later I will have forgotten , or if someone uses my code they shouldn't need an explaination. Mark

dmaruska · Answer

George, Give this a try. I'm assuming that you are using the D I/O 13 - 10, and the Button press (pin 10) is low to hi when pressed. LEDS are off when low outputs are on D I/O 13 to 11. I'm sure there are more ways to do this, but I wrote this and its seems to test ok on the simulator. //LED SEQUENCER WITH BUTTON int ledPin1 = 13; int ledPin2 = 12; int ledPin3 = 11; int butPress1 = 10; int countBP = 0; void setup() { pinMode(ledPin1, OUTPUT); pinMode(ledPin2, OUTPUT); pinMode(ledPin3, OUTPUT); pinMode(butPress1, INPUT); } void loop() { digitalWrite(ledPin1, LOW); digitalWrite(ledPin2, LOW); digitalWrite(ledPin3, LOW); countBP = digitalRead(butPress1); while (countBP != 0) { switch (countBP) { if (countBP == 0) { case 1: digitalWrite(ledPin1, HIGH); digitalWrite(ledPin2, LOW); digitalWrite(ledPin3, LOW); countBP = countBP + digitalRead(butPress1); break; } if (countBP == 1) { case 2: digitalWrite(ledPin1, LOW); digitalWrite(ledPin2, HIGH); digitalWrite(ledPin3, LOW); countBP = countBP + digitalRead(butPress1); break; } if (countBP == 2) { case 3: digitalWrite(ledPin1, LOW); digitalWrite(ledPin2, LOW); digitalWrite(ledPin3, HIGH); countBP = countBP + digitalRead(butPress1); break; } default: digitalWrite(ledPin1, LOW); digitalWrite(ledPin2, LOW); digitalWrite(ledPin3, LOW); countBP = 0; break; } } }

Simple LED Sequence with Button Question..

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