$/*$ Seven$-$segment display counter

$*$

$*$ This program counts number $0-3$ on the seven segment display.

$*$ The seven segment display is driven by a shift register which is

$*$ connected to SSI$2$ in SPI mode.

$*$

$*$ Built and tested with Keil MDK$-$ARM v$5\mathrm{.}28$ and TM$4$C$\_$DFP v$1\mathrm{.}1\mathrm{.}0$

$*/$

#include $"$TM$4$C$123.$h$"$

void delayMs$($int n$)$;

void sevenseg$\_$init$($void$)$;

void SSI$2\_$write$($unsigned char data$)$;

int main$($void$)\{$

const static unsigned char digitPattern$[]=\{0$xB$0,0$xA$4,0$xF$9,0$xC$0\}$;

int i;

sevenseg$\_$init$()$; $//$ initialize SSI$2$ that connects to the shift registers

while$(1)\{$

SSI$2\_$write$($digitPattern$[$i$])$; $//$ write digit pattern to the seven segments

SSI$2\_$write$((1<<$ i$))$; $//$ select digit

if $(++$i $>3)$

i $=0$;

delayMs$(4)$; $//1000/60/4=4\mathrm{.}17$

$\}$

$\}$

$//$ enable SSI$2$ and associated GPIO pins

void sevenseg$\_$init$($void$)\{$

SYSCTL$->$RCGCGPIO $|=0$x$02$; $//$ enable clock to GPIOB

SYSCTL$->$RCGCGPIO $|=0$x$04$; $//$ enable clock to GPIOC

SYSCTL$->$RCGCSSI $|=0$x$04$; $//$ enable clock to SSI$2$

$//$ PORTB $7,4$ for SSI$2$ TX and SCLK

GPIOB$->$AMSEL &$=$ ~$0$x$90$; $//$ turn off analog of PORTB $7,4$

GPIOB$->$AFSEL $|=0$x$90$; $//$ PORTB $7,4$ for alternate function

GPIOB$->$PCTL &$=$ ~$0$xF$00$F$0000$; $//$ clear functions for PORTB $7,4$

GPIOB$->$PCTL $|=0$x$20020000$; $//$ PORTB $7,4$ for SSI$2$ function

GPIOB$->$DEN $|=0$x$90$; $//$ PORTB $7,4$ as digital pins

$//$ PORTC $7$ for SSI$2$ slave select

GPIOC$->$AMSEL &$=$ ~$0$x$80$; $//$ disable analog of PORTC $7$

GPIOC$->$DATA $|=0$x$80$; $//$ set PORTC $7$ idle high

GPIOC$->$DIR $|=0$x$80$; $//$ set PORTC $7$ as output for SS

GPIOC$->$DEN $|=0$x$80$; $//$ set PORTC $7$ as digital pin

SSI$2->$CR$1=0$; $//$ turn off SSI$2$ during configuration

SSI$2->$CC $=0$; $//$ use system clock

SSI$2->$CPSR $=16$; $//$ clock prescaler divide by $16$ gets $1$ MHz clock

SSI$2->$CR$0=0$x$0007$; $//$ clock rate div by $1,$ phase$/$polarity $00,$ mode freescale, data size $8$

SSI$2->$CR$1=2$; $//$ enable SSI$2$ as master

$\}$

$//$ This function enables slave select, writes one byte to SSI$2,$

$//$ wait for transmit complete and deassert slave select.

void SSI$2\_$write$($unsigned char data$)\{$

GPIOC$->$DATA &$=$ ~$0$x$80$; $//$ assert slave select

SSI$2->$DR $=$ data; $//$ write data

while $($SSI$2->$SR & $0$x$10)\{\}//$ wait for transmit done

GPIOC$->$DATA $|=0$x$80$; $//$ deassert slave select

$\}$

$/*$ delay n milliseconds $(50$ MHz CPU clock$)*/$

void delayMs$($int n$)\{$

int i$,$ j;

for$($i $=0$ ; i$<$ n; i$++)$

for$($j $=0$; j $<6265$; j$++)$

$\{\}/*$ do nothing for $1$ ms $*/$

$\}$