Page 422 - Programming Microcontrollers in C

Serial Input/Output 407

/* return TRUE when a key has been hit and FALSE otherwise */
int kbhit(void)
{
return U1RX.CHARRDY;
}

/* convert a long to a series of ascii characters
and send it out the serial port */
void printd(unsigned long x)
{
if(x/10)
printd(x/10);
putchar(x%10+’0');
}

/* same as above but output hexidecimal */
void printx(unsigned long x)
{
if(x/16)
printx(x/16);
putchar(x%16+((x%16>9)?(‘a’):(‘0’)));
}
Listing 8-5: Serial Input/Output Functions

At the beginning of the program, the usual headers are included.
In this case, mmc2001.h is needed to identify the address of the
UART, the header uart.h contains all of the definitions needed for
the UART registers, and the serial.h header contains function
prototypes for all of the serial input/output functions. These functions
are for demonstration purposes only. They all work. I have used these
functions at 115200 bit rates and had no problems. None of them
have any built-in tests for errors on reception like parity tests, framing
errors, or overrun errors. These tests need to be included and the
errors handled properly if you want to have a production quality
input/output library.
In the text that follows, each of the several small functions
contained in the above listing will be described individually. The
first function is the inituart() function.

#include “mmc2001.h”
#include “uart.h”
#include “serial.h”