I want to convert DS18B20( [link removed by moderator]: )
temperature (4-bytes code from datasheet) to string with accuracy 0.1°C (like sprintf %.1f). AVR. C language (avr-gcc). I need for small code, so sprintf, floating-point types and round from math.h is bad idea. My following current code is bad also:

void reverse_string(char *s)
{
char *p, c;

for (p = s + strlen(s) - 1; s <= p; ++s, --p) {
    c = *p;
    *p = *s;
    *s = c;
}

}

void ts_to_string(uint16_t ts, char *s)
{
int8_t n = (int8_t)(ts >> 4);
uint8_t neg = n & 0x80;
char *p = s;
float f;

if (neg)
    n = -n-1;
do {
    *p++ = n % 10 + '0';
} while ((n /= 10) > 0);

if (neg)
    *p++ = '-';

*p = '\0';
reverse_string(s);
*p++ = '.';

f = (float)(ts & 0xf) / 16.0;
if (neg)
    f = 1.0-f;
*p++ = (char)round(f * 10.0) + '0';
*p = '\0';