Defining char types

Projects Programming
1

Hi, I'm running this code to convert a date from individual char types to one dec number.
unsigned long date_convert() { //converts 6 ascii digits in eprom_date array into integer returned

When my input is > 39999 I get a huge incorrect final value out. I need to convert up to 92000.

I'm really messing with caller ID dates but I think for our purposes it doesn't matter.

I feel like the unsigned long should be ok.
Any help would be appreciated.

 unsigned long retval = 0;   //

  eprom_date[0] = '3';    // test values  (want to go up to 92000 here
  eprom_date[1] = '9';
  eprom_date[2] = '9';
  eprom_date[3] = '9';
  eprom_date[4] = '9';

  retval =  (eprom_date[0]  - 0x30)  * 10000;  // year ones
  retval +=  (eprom_date[1]  - 0x30)  * 1000;  // month tens
  retval +=  (eprom_date[2]  - 0x30)  * 100;   // month ones
  retval +=  (eprom_date[3]  - 0x30)  * 10;    // day tens
  retval +=  (eprom_date[4]  - 0x30);          // day ones

  Serial.print("Date Convert= ");    Serial.println(retval, DEC);   // expect 39999 here
  return (retval);
2

Don't post snippets (Snippets R Us!)

Your math such as (eprom_date[0] - 0x30) * 10000; is conducted using int
an int on an 8 bit microcontroller goes to 32767
if you want to make that unsigned long math, you need to force the data type adding ul to the literals for example

  retval =  (eprom_date[0]  - 0x30ul)  * 10000ul;  // year ones
1 Like
3

This is all of the code except the void date_convert () { } at the end.

4

I edited my post whilst you were typing

(still don't post snippets, for example we don't know the type and size of the eprom_date array)

5

You're right. I know the array sizes are OK but should have shown it.

The "UL"'s worked. Thanks very much. !

6

great :slight_smile:

have fun

PS/

probably more readable as

  retval  =  (eprom_date[0]  - '0')  * 10000ul;  // year ones
  retval +=  (eprom_date[1]  - '0')  * 1000ul;   // month tens
  retval +=  (eprom_date[2]  - '0')  * 100ul;    // month ones
  retval +=  (eprom_date[3]  - '0')  * 10ul;     // day tens
  retval +=  (eprom_date[4]  - '0');             // day ones

PS2/ you'd probably be better off to store the unsigned long in EEPROM rather than the ASCII representation and use get() and put()

7

That is easier to read. Thanks for the tip.

8 
unsigned long retval = 0;   //

  eprom_date[0] = '3';    // test values  (want to go up to 92000 here
  eprom_date[1] = '9';
  eprom_date[2] = '9';
  eprom_date[3] = '9';
  eprom_date[4] = '9';

  for (byte i=0;i<4;i++)retval = (eprom_date[i] - '0') + retval * 10;
  
  Serial.print("Date Convert= ");    Serial.println(retval, DEC);   // expect 39999 here
  return (retval);
9

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