Hello everyone. I am vignesh raja. Here we are going to see about
how to implement multitasking concept in msp430. Multi Tasking is defined as
doing two or more function at same time but independently each other. One
function doesn’t affect other function. Basically when we use delay function in
the program of microcontroller when delay function runs we can’t do any other
function and condition checking except interrupt. Because delay function use
whole cpu. Instead of delay we are going to use millis() function from energia
software’s pre de fined functions. Using this millis() function we are going to achieve multi tasking. The msp430 ic has inbuilt
timer. What millis() function does is that running time on that timer when ic
get powered. It prints the count of current millisecond. If ic runs for exactly
one second from when it powered it print count of millisecond as 1000. Because
the 1000ms is equal to one second. The milis() count approximately get counts
for 53 day . After 53 days it get resetted
. but no problem the resetting doesn’t affect output.
Here in this video I programmed msp430 launch pad to perform
two functions run at the same time. One function led blink with interval of one
second and other function is when the push button pressed then it will print
some string in serial monitor. Here what I did to provide delay between led blinking
is just seeing the millis() function time using if condition . it just like we
watch the time and do work as per time. At first The program set the millis()
value into a variable (current_Millis)
and assign a variable(previous_Millis) with zero value. And IF condition
check subtraction between current_Milis variable and previous_Millis variable
equal to 1000. If the condition is true then it changes the current led state.
If led is high then it become low and vice versa. So here we are didn’t using
delay instead of that we are using condition checking for time. So at mean time
of this function the cpu is free. So it can able to check other function also.
So here I did other function push button checking. So both function work at same time. Multi
tasking is achieved in the microcontroller. Below I provide the code use it and
share your opinion in comment.
coding:
const int ledPin = P1_0; // set P1.0 as led pin
int button = P1_3; // P1.3 conneted with push button in msp430 board
int ledState = LOW; // led state
long previousMillis = 0; // hold last millis value
long interval = 1000; // time intervel to provide delay for led function
void setup() {
pinMode(ledPin, OUTPUT); // set led pin as output
pinMode(button, INPUT); // set button as input
Serial.begin(4800); // start serial communication at the baud rate of 4800
}
void loop()
{
unsigned long currentMillis = millis(); // saving current millis() value to a variable
if(currentMillis - previousMillis > interval) { //comparing subtraction of current millis value to privious millis value with intervel 1000ms = 1 sec
previousMillis = currentMillis; // after comparision assigning current millis to previous one
if (ledState == LOW) //check led state if it is low make it as high
ledState = HIGH;
else
ledState = LOW; // if it is high make it as low
digitalWrite(ledPin, ledState);
}
if (digitalRead(button)== LOW){ // check button is pressed
Serial.println("button pressed!"); // if true then print this string serial monitor
}
}
Thank you for reading.
