Howto redirect (convert from hex to dec/Serial.print) fcn output into a var?

Projects Programming
6

Ok, I have been poring over the linux man pages for (s)printf, and have come up with:

char SD_datetime[100];

 sprintf(SD_datetime, "%s-%s-%s-%.2d-%.2d-%.2d", r[6], r[5], r[4], r[2], r[1], r[0]);
  Serial.print("||||| sprintf version: ");
  Serial.print(SD_datetime);
  Serial.print("|||||");

where the r array is filled by

readDS1307(0, r, 8)

and readDS1307() is

uint8_t readDS1307(uint8_t address, uint8_t *buf, uint8_t count) {
  // issue a start condition, send device address and write direction bit
  if (!rtc.start(DS1307ADDR | I2C_WRITE)) return false;

  // send the DS1307 address
  if (!rtc.write(address)) return false;

  // issue a repeated start condition, send device address and read direction bit
  if (!rtc.restart(DS1307ADDR | I2C_READ))return false;

  // read data from the DS1307
  for (uint8_t i = 0; i < count; i++) {

    // send Ack until last byte then send Ack
    buf[i] = rtc.read(i == (count-1));
  }

  // issue a stop condition
  rtc.stop();
  return true;
}

The output I get is... blank.

Krupsi, I will next work on adapting your example into the code to see what happens. Thank you for providing a detailed answer!