HEX, INT, BYTE ... Can I simplify this code?

Using Arduino Programming Questions
1

Hi,

I somehow got this working. But for me it looks like there should be a simpler way. Can I simplify this code and avoid the sprintf / buffer somehow?

// uint64_t pt = 0x1105202216300000;

char buf1[5];
sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 32)));
ds3231.setYear((byte)(String(buf1).toInt()));

sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 48)));
ds3231.setMonth(String(buf1).toInt());

sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 56)));
ds3231.setDate(String(buf1).toInt());

sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 24)));
ds3231.setHour(String(buf1).toInt());

sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 16)));
ds3231.setMinute(String(buf1).toInt());

sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 8)));
ds3231.setSecond(String(buf1).toInt());

greetings and thanks,
André

2

If you start with an int, why convert it to a string, then to a String, then back to an int?

sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 32)));
ds3231.setYear((byte)(String(buf1).toInt()));


ds3231.setYear((byte)( pt >> 32));
3

Seems to me that this can be written as:

ds3231.setMonth(pt >> 48);

(edit)

You probably also need to use AND to select a certain number of bits, e.g.,

ds3231.setMonth((pt >> 48) & 0xff);
4

isn't there a problem with these values being in hex?

hex 22 is 34 decimal. the individual nibbles (4-bits) need to be teased out and combined to create a decimal value

#include <stdio.h>
#include <stdint.h>

uint64_t pt = 0x1105202216300000;
uint8_t  *p = (uint8_t*) & pt;

void
set (
    uint8_t     val,
    const char *lbl )
{
    int dec;
    dec  = val & 0xF;
    dec += (val >> 4) * 10;

    printf ("set: %02x  %02d  %s\n", val, dec, lbl);
}

int
main ()
{
    printf (" %llx\n", pt);

    for (int i = 0; i < sizeof(uint64_t); i++)
        printf (" %02x", p [i]);
    printf ("\n");

    set (p [7], "month");
    set (p [6], "day");
    set (p [4], "year");
    set (p [3], "hour");
    set (p [2], "minute");

    return 0;
}

the format is awkward unless it really is intended to be interpreted as nibbles

5

sadly, the bit mask does not work.

ds3231.setYear((pt >> 32) & 0xff);

result: 34

sprintf_P(buf1, PSTR("%02x"), ((byte)(pt >> 32)));
ds3231.setYear(String(buf1).toInt());

result: 22

6

Here is a useful function:


byte bcdToNumber(byte b) {
  // convert BCD (binary-coded decimal) to an ordinary number
  byte tens = (b >> 4) & 0xF;
  byte ones = b & 0xF;
  return (byte)((tens * 10) + ones);
}

That function allows you to do this:

ds3231.setYear(bcdToNumber((byte)((pt >> 32) & 0xff)));
7

You might want tot post your entire sketch, so we can see the actual format of pt.

8

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