Finished lab notes for labs 3 and 4
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@ -4,7 +4,7 @@
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\usepackage{fullpage}
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\usepackage{minted}
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%{\renewcommand\fcolorbox[4][]{\textcolor{red}{\strut#4}}
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\usepackage{siunitx}
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\begin{document}
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\maketitle
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@ -26,7 +26,7 @@ GDB = $(GCC_DIR)/msp430-elf-gdb
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CFLAGS = -I $(SUPPORT_FILE_DIRECTORY) -mmcu=$(DEVICE) -Os -g
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LFLAGS = -L $(SUPPORT_FILE_DIRECTORY) -T $(DEVICE).ld
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all: prog1 prog2 adc pwm
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all: prog1 prog2 adc pwm dimmer
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prog1: prog1.c
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$(CC) $(CFLAGS) $(LFLAGS) $? -o prog1.elf
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@ -40,17 +40,17 @@ adc: adc.c
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pwm: pwm.c
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$(CC) $(CFLAGS) $(LFLAGS) $? -o pwm.elf
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$(CC) $(CFLAGS) $(LFLAGS) $? -S -o pwm.asm
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debug: all
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$(GDB) ${EXEC}
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dimmer: dimmer.c
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$(CC) $(CFLAGS) $(LFLAGS) $? -o dimmer.elf
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$(CC) $(CFLAGS) $(LFLAGS) $? -S -o dimmer.asm
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clean:
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rm prog1.elf prog2.elf adc.elf pwm.elf prog1.asm prog2.asm adc.asm pwm.asm
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rm prog1.elf prog1.asm prog2.elf prog2.asm adc.elf adc.asm \
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pwm.elf pwm.asm dimmer.elf dimmer.asm
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\end{minted}
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\section{Program 1}
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Compiling from C, the produced Assembly file has a \textit{lot} of extra code, and appears to have been optimized differently. Below is the relevant section of the compiled .asm with some comments comparing lines to last lab's prog1.asm code.
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\begin{minted}{gas}
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.LCFI0:
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.loc 1 21 0
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@ -91,10 +91,8 @@ clean:
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.loc 1 26 0 discriminator 1
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BR #.L6 ; loop from top of loops
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\end{minted}
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\newpage
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This was generated using the following C code that doubles the count and thus halves the blinking rate.
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\begin{minted}{c}
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#include <msp430.h>
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@ -118,7 +116,6 @@ void main(void) {
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\section{Program 2}
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Below is the C code used to make the LEDs blink in the red--green--both--none pattern, using the same XOR trick described in the last lab notes.
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\begin{minted}{c}
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#include <msp430.h>
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@ -148,8 +145,218 @@ void __attribute__ ((interrupt(PORT1_VECTOR))) PORT1_ISR(void) {
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\end{minted}
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\section{Analogue to Digital Conversion}
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\section{Pulse Width Modulation}
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For a 3.3 V CMOS input, $V_{\textrm{IH}} \ge \SI{2}{V}$ and $V_{\textrm{IL}} \le \SI{0.8}{V}$. The ADC scale goes up to 0x3FF, but according to the provided C program, $V_{\textrm{IH}} \ge \texttt{0x2FF} = 767$. Assuming the ADC scale is linear with voltage and that it begins at 0 V, we have $V_{\textrm{LH}} \le \SI{0.8}{V} * \frac{767}{\SI{2}{V}} = 307 = \texttt{0x133}.$ Below is the code for lighting up the red LED on HI, the green LED on LO, and a yellow LED connected to P1.2.
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\begin{minted}{c}
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#include "msp430.h"
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void main(void) {
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WDTCTL = WDTPW + WDTHOLD; // Stop WDT
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ADC10CTL0 = ADC10SHT_2 + ADC10ON; // ADC10ON
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ADC10CTL1 = INCH_1; // input A1
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ADC10AE0 |= 0x02; // PA.1 ADC option select
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P1DIR |= 0x45; // Set P1.0 to output direction
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while (1) {
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ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
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while (ADC10CTL1 & ADC10BUSY); // ADC10BUSY?
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P1OUT &= ~0x45; // clear all LEDs first
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if (ADC10MEM > 0x2FF) { // HI > 2 V (767 on scale)
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P1OUT |= 0x01; // set red LED on HI
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} else if (ADC10MEM < 0x133) { // LO < 0.8 V (307 on scale)
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P1OUT |= 0x40; // set green LED on LO
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} else { // in-between otherwise
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P1OUT |= 0x04; // set yellow LED connected to P1.2
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}
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unsigned i;
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for (i = 0xFFFF; i > 0; i--); // Delay
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}
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}
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\end{minted}
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\section{LED Dimmer}
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Below is the code combining the ADC and the PWM to create a dimmer when the output of the PWM is connected to an LED. We take the sampled voltage as usual and set the duty cycle to a fraction of the period according to the sample, out of \texttt{0x3FF}.
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\begin{minted}{c}
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#include "msp430.h"
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void main(void) {
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WDTCTL = WDTPW + WDTHOLD; // Stop watchdog
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ADC10CTL0 = ADC10SHT_2 + ADC10ON; // ADC10ON
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ADC10CTL1 = INCH_1; // input A1
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ADC10AE0 |= 0x02; // PA.1 ADC option select
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P1DIR |= BIT2; // P1.2 to output
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P1SEL |= BIT2; // P1.2 to TA0.1
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CCR0 = 1000-1; // PWM period
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CCTL1 = OUTMOD_7; // CCR1 reset/set
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TACTL = TASSEL_2 + MC_1; // SMCLK, up mode
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while (1) {
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ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
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while (ADC10CTL1 & ADC10BUSY); // ADC10BUSY?
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CCR1 = (1000 * ADC10MEM) / 0x3FF; // CCR1 PWM duty cycle set to percentage
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// of sampled voltage out of maximum
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for (volatile unsigned int i = 0xFFFF; i > 0; i--);
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}
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}
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\end{minted}
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\section{Sing!}
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By changing the period of the PWM, we can change the pitch of the tone produced by the piezoelectric buzzer, which means we can make it sing by changing pitches in appropriate intervals. The below makes the buzzer sing Happy Birthday. When connected to the four-digit seven-segment display, it will also display the note being played.
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\begin{minted}{c}
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#include "msp430.h"
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// these aren't actually tuned to those notes,
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// they're just named chromatically for convenience
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#define c 1000
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#define dflat 950
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#define d 900
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#define eflat 850
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#define e 800
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#define f 750
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#define gflat 720
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#define g 670
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#define aflat 625
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#define a 600
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#define bflat 570
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#define b 535
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#define cc 500
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#define n 0
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// notes of happy birthday
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int hbd[30] = {
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c, n, c,
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d, c, f,
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e, c, n, c,
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d, c, g,
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f, c, n, c,
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cc, a, f,
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e, d, bflat, n, bflat,
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a, f, g,
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f, n
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};
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// relative length of each note
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int hbd_lengths[30] = {
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1, 1, 1,
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3, 3, 3,
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6, 1, 1, 1,
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3, 3, 3,
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6, 1, 1, 1,
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3, 3, 3,
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3, 6, 1, 1, 1,
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3, 3, 3,
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6, 3
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};
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int scale[13] = {
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c, dflat, d, eflat, e, f, gflat, g, aflat, a, bflat, b, cc
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};
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int scale_lengths[13] = {
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
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};
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// P1 pin assignment
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// 7 6 4 5 3 2 1 0
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// ..note.. str out A1 A0
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// show the name of the note in the first (rightmost) digit
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// N.B. G displayed as 6
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unsigned char show(int note) {
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switch (note) {
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case c:
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case cc:
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return 0xc0;
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case d:
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case dflat:
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return 0xd0;
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case e:
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case eflat:
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return 0xe0;
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case f:
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return 0xf0;
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case g:
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case gflat:
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return 0x60;
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case a:
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case aflat:
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return 0xa0;
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case bflat:
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case b:
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return 0xb0;
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default:
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return 0x00;
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}
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}
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// if the note is a flat, show F in the second digit
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// if the note is a high C, show as CC
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unsigned char acc(int note) {
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switch (note) {
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case bflat:
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case dflat:
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case eflat:
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case gflat:
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case aflat:
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return 0xf1;
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case cc:
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return 0xc1;
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default:
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return 0x01;
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}
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}
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// argument: one of the notes defined at top
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// used as period for PWM
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// if 0, set duty cycle to 0 to silence
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void play(int note) {
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if (note != 0) {
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CCR0 = note;
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CCR1 = 100;
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} else {
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CCR1 = 0;
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}
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}
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// strobe output to display
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void display(unsigned char out) {
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P1OUT = out;
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P1OUT |= 0x08;
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}
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void sing(int* song, int* song_lengths, int length) {
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while (1) {
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for (int i = 0; i < length; i++) {
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int note = song[i];
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play(note); // set pitch
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display(show(note); // show note
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display(acc(note)); // show if flat
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// set delay by length of note
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for (volatile unsigned int length = song_lengths[i]; length > 0; length--) {
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for (volatile unsigned int i = 0x3000; i > 0; i--);
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}
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}
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}
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}
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// set all digits of display to 0
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void clear() {
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for (unsigned char i = 0; i < 4; i++) {
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P1OUT = i;
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P1OUT = i | 0x08;
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}
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}
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void main(void) {
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WDTCTL = WDTPW + WDTHOLD; // Stop WDT
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P1DIR = 0xFF; // all set to output
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P1SEL |= BIT2; // P1.2 to TA0.1
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CCTL1 = OUTMOD_7; // CCR1 reset/set
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TACTL = TASSEL_2 + MC_1; // SMCLK, up mode
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clear();
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sing(hbd, hbd_lengths, 30);
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//sing(scale, scale_lengths, 13);
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}
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\end{minted}
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\end{document}
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