I have a standard c function with the following prototype
extern void lcd_puts(const char *s);
in my other function i have something like this
send_to_lcd() {
uint8_t count = 10
lcd_puts(count);
}
my question is how do i convert count to a string pointer to be able to send it to lcd_puts which should print out the count on a lcd screen
thanks
On a microcontroller, you have to be at least a little worried about performance (which rules out sprintf), even division is a very expensive operation on such chips. So you want code optimized for a microcontroller.
I've written some here: http://ideone.com/SsEUW (will need a few changes for use with C-style strings instead of C++, but the method should be clear)
itoa as suggested by Owen might be feasible, but sprintf is a horrible choice on a microcontroller.sprintf is the best choice here; it's a widely-supported standard library function (one can't say the same for itoa).
sprint would be fine, if he's writing to an LCD screen it's not like you're gonna see the 1 ms (1000 cycles on 1MHz proc) or so delay. Be careful with it though because a lot of embedded libraries use a stripped-down, non-standard sprintf that might not do what you expect (like always print in Hex (PIC for %ld)), or none at all
It depends on what lcd_puts does with its argument. One possibility is as follows:
void send_to_lcd(uint8_t count)
{
char str[SOME_CONSERVATIVE_MAX_LENGTH];
sprintf(str, "%d", count); // You might also snprintf() if it's available
lcd_puts(str);
}
But remember that str goes out of scope as soon as send_to_lcd() returns. So if lcd_puts "remembers" its input argument, this will have undefined behaviour.
If that's the case, you will have to malloc a string buffer instead. But then you'll need to remember to free() it at some point, and it all gets rather messy.
malloc(), you could use a static buffer (but I don't think lcd_puts saves it's argument -- it's probably just setting digital pins).sprintf_P instead (nongnu.org/avr-libc/user-manual/…)
This seems like a reasonable approach.
#include <stdint.h>
#include <stdio.h>
const char *u82s(uint8_t count)
{
static char aString[4];
aString[3] = '\0';
aString[2] = (count % 10) + '0'; count /= 10;
aString[1] = (count % 10) + '0'; count /= 10;
aString[0] = (count % 10) + '0';
return aString;
}
int main(void)
{
uint8_t z = UINT8_MAX;
do
{
z++;
printf("%s\n", u8ts(z));
}
while (z != UINT8_MAX);
return 0;
}
printf anyway?
sprintf will format a string
Quick example:
char buf[50];
uint8_t count = 10;
sprintf(buf,'%d',count);
lcd_puts(buf);
Taking your api as a basis.
/* One assumes this is a function that somehow displays a c string on the lcd. */
extern void lcd_puts(const char *s);
send_to_lcd()
{
uint8_t count = 10; /* This is the variable to send to the screen */
lcd_puts(u82s(count)); /* This creates a string representation of count, */
} /* which is then passed to the lcd_puts function */
/* giving you the result you are after. You question */
/* was how to make a c string out of a uint8. */
/* this is a way to do it. */
It is basically the same as the answer you picked. Convert the value count into a c string, so that lcd_puts can use it.
Removed static and tidied up:
void UART_SendInt( uint16_t num )
{
#define MAX_LEN 6 // 32767 is 6 characters with NULL terminator
#define BASE_10 10 // Print decimal format
uint8_t index = MAX_LEN - 1;
char str[ MAX_LEN ];
str[ index ] = '\0';
while( index-- )
{
str[ index ] = ( num % BASE_10 ) + '0';
num /= BASE_10;
if( 0 == num )
{
UART_SendStr( &str[ index ] );
break;
}
}
UART_SendStr( "\r\n" );
return;
}
I can't print above 32767 but i think that's something to do with my compiler options.
itoaorsprintf?