Microcontrollers JULES CALELLA

Microcontrollers vs Microprocessors  Microprocessors – do not contain RAM, ROM, I/O  Microcontrollers – The whole package (mini computer)

Where are Microcontrollers Used?  Mouse, toys, phones, game controllers, etc.  Anything that requires complex instructions but doesn’t need a full OS

How Do You Control a Microcontroller?  Programming in C or Assembly  C – slower, good starting point for beginners, easy to debug  Timing doesn’t work as expected

Microchip’s Models  8-bit Start here  16-bit (includes dsPIC)  32-bit

Using the Data Sheet  Contains everything about the device  Summary of modules  Pinout  Dimensions  Registers

Errata Sheet  Revisions and mistakes

Configuration Bits  Oscillator  Watchdog timer  Brown-out reset  Every model offers different options

Oscillator  Controls the timing  Internal or external  4MHz, 8MHz (PLL)

 OSCCON = 0xD2 ( )  OSCCONbits.IRCF = 0x5

GPIO  TRIS – output (0) or input (1)  LAT – Turn ON (1) or OFF (0)  PORT – Read ON (1) or OFF (0)

Example: TRISA = 0x00; //All are outputs LATAbits.LATA5 = 1; //Turn LED on char pinState = PORTAbits.RA5; //Determine if LED is on

ADC  Analog-to-digital converter  10 – 14 bit resolution  Reference voltage (increase sensitivity)  Only some ports have functionality (ANSx)  Temperature sensors, light sensors, potentiometers, pressure sensors

 ANSx = 1  TRISx = 1//Disables digital output driver  Left justifiedx x x x x x x x x x _ _ _ _ _ _  Right justified_ _ _ _ _ _ x x x x x x x x x x  Time Acquisition

Interrupts  Practically every module has one  Interrupt Flags  Priority

Timers  Hardware based counters with interrupts  8, 16, 32 bit timers  Divisible  Used as timer or counter

void interrupt Timer0_ISR(void) { if (T0IE && T0IF) { T0IF = 0; //Perform some task (e.g. blink LED) //LATA = !LATA; TMR0 = 4; //Depends on how long task takes }

Communication  UART – slow, 2-wire, asynchronous  I2C – faster, 2-wire, synchronous  SPI – fastest, 3-4 wires, synchronous  Controllable Baud Rate  USB – able to communicate with USB hosts

Wires for Communication  UART – RX & TX  I2C – Data & Clock  SPI – SS, SCLK, SDO, SDI

USB  4 wires (PWR, D+, D-, GND)  Host mode and Device mode  Internal USB PLL offers higher clock rate  Look up and download “Microchip MLA”

Peripheral Pin Select  Modules multiplexed amongst pins  Allows the user to move the modules to desired pin  Requires an unlock sequence

#include //PRAGMAS //Defines and Global Initializations //Timer Function int main(){ OSCCON = 0x00;//Set up or functions for setup TRISA = 0xF0;//Half input, half output //Don’t forget de-bounce when using buttons while(1) { //Program here } return 0; //You should not reach this point }

Debugging  For WHEN your program doesn’t run as expected  Break points  Stopwatch  Watch (variables)  In-circuit debugging

How To Get Started  Programmer/debugger (Pickit 3)  Starter board (8-bit recommended)  Additional microcontrollers  IDE (MPLAB X)  Compiler (XC or mikroC)  Breadboard, LEDs, etc.  A book with code examples (optional, but not really…)

Final Tips  Learn how to display data (LEDs/LCD/computer)  Use binary operations  Make sure IC’s are shipping from the U.S.  Ensure Oscillator works correctly  Make small programs to test functions  Review Microchip’s tutorial documents  Join forums to ask people for help  

Thank You  Questions?