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// Source: Programmable Microcontrollers with Applications, p.115
// Turning on the red LED when the push button is pressed
// MSP430 LaunchPad Rev.1.5

#include <msp430g2553.h>

#define LED BIT0                        // P1.0
#define BUTTON BIT3                     // P1.3

void main(void){

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* Model for uA741 Op Amp (from EVAL library in PSpice)
* connections: non-inverting input
* | inverting input
* | | positive power supply
* | | | negative power supply
* | | | | output
* | | | | |
*
.subckt uA741 1 2 3 4 5
*

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// Source: Programmable Microcontrollers with Applications, p.117
// Toggling the green LED when the push button is pressed
// MSP430 LaunchPad Rev.1.5

#include <msp430g2553.h>

#define LED BIT6                        //P1.6 LED2
#define BUTTON BIT3                     //P1.3 S2

void delay_ms(int);                     // declare function delay_ms

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// a PWM signal is created with the TimerA0 where CCR0 is the periode 20ms and CCR1 the duty cycle
// the PWM signal is output through pin P1.6 that correspond to TA0.1 (see MSP430G2553 uC datasheet)
// this code does not generate interruptions but uses the reset/set mode to generate the PWM signal when the timer counts up to CCR1
// in this case a duty cycle of 2ms (CCR1 = 2000 - 1) will rotate the axis clockwise (see sg90 datasheet)
// a duty cycle of 1.0ms (CCR1 = 1000 - 1) will rotate the axis anticlockwise
// a duty cycle of 1.5ms (CCR1 = 1500 - 1) will rotate the axis to the center position
// the servo used was a sg90 but I guess the code will work with any servo (refer to the servo's datasheet to confirm this)

#include <msp430g2553.h>

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// test external crystal by observing ACLK frequency on ACLK pin
// ACLK correspond to pin P1.0 in MSP430G2553 (see MSP430G2553 datasheet)
// an external crystal connects to the XIN, XOUT pins
// XIN and XOUT correspond to pins P2.6 and P2.7 respectively in MSP430G2553 (see MSP430G2553 datasheet)
// P1SEL = BIT0 and P1DIR = BIT0 show ACLK in P1.0 (see MSP430G2553 datasheet, pin functions)
// this only works with small crystals in cylindrical package

// stand-alone uC test:
// DVCC to 3.3V
// DVSS to GND

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// source current to a LED through digital pin 7
// connection: pin7 set to high - LED's anode .. LED's cathode - 1k resistor - GND
// LED's anode (+) long terminal
// LED's cathode (-) short terminal
// 1k resistor color code: brown black red
// code executed on Arduino Leonardo

void setup(){
  pinMode(7, OUTPUT);
}

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// sink current through a LED to digital pin 7
// connection: VCC - LED's anode .. LED's cathode - 1k resistor - pin7 set to low
// VCC is 5V
// LED's anode (+) long terminal
// LED's cathode (-) short terminal
// 1k resistor color code: brown black red
// code executed on Arduino Leonardo

void setup(){
  pinMode(7, OUTPUT);

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void setup(){
  pinMode(7, OUTPUT);
}

void loop(){
  digitalWrite(7, HIGH);
  delay(500);
  digitalWrite(7, LOW);
  delay(500);
}

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// turn LED ON and OFF using switch
// we read the state of the switch through pin 7
// switch is connected between pin 7 and GND
// we use the microcontroller's internal 20k pullup resistor
// why do we use a pullup resistor? read here: https://learn.sparkfun.com/tutorials/pull-up-resistors
// you can choose between LED ON or LED OFF when switch is pressed
// pin 8 will source current to the LED
// refer to source_current.ino file to see how to connect the LED
// code executed on Arduino Leonardo

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// PWM signal through pin 3
// 8 bits PWM: 0 (0% or GND) to 255 (100% or VCC)
// what's a PWM signal? read here: https://en.wikipedia.org/wiki/Pulse-width_modulation
// pin 3 will source current to the LED
// refer to source_current.ino file to see how to connect the LED
// code executed on Arduino Leonardo

void setup(){
  pinMode(3, OUTPUT); // observe that only pins preceded by ~ in the board can output a PWM signal
}