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RE: [avr-gcc-list] Possible bug in avr-gcc 4.3.2?
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From: |
Michael |
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Subject: |
RE: [avr-gcc-list] Possible bug in avr-gcc 4.3.2? |
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Date: |
Tue, 26 May 2009 10:46:55 +1000 |
I think I may know the problem.
Not only are your strings are stored in program memory, but also your
pointers to these strings are stored in program memory.
So the line:
> lcd_write_int16(dow[k]); lcd_putc(','); // outputs: address in dow[1]
Does not actually output the address of "Pon", but the address in
program memory of which the pointer to "Pon" is stored.
If you remove PROGMEM from the following line, I believe your code will
run as expected.
> PGM_P dow[] PROGMEM = { dow0, dow1, dow2, dow3, dow4, dow5, dow6 };
Otherwise you will need to call functions to read the PGM_P's stored in
progmem into actual PGM_P's.
There is a good progmem tutorial in the forum section on avrfreaks:
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=38003
Regards, Michael.
> -----Original Message-----
> From: address@hidden
[mailto:avr-
> address@hidden On Behalf Of Zoran
Rilak
> Sent: 24 May 2009 02:09
> To: address@hidden
> Subject: [avr-gcc-list] Possible bug in avr-gcc 4.3.2?
>
> Hi all,
>
> I am fairly new to the world of uC programming. I've been using
avr-gcc
> 4.3.2 with ATmega168 and stumbled upon something rather peculiar.
> Please consider the following code snippet (the crux of the matter is
in
> the last block of code):
>
> #include "lcd.c"
>
> // Day-of-week names
> char dow0[] PROGMEM = "Ned";
> char dow1[] PROGMEM = "Pon";
> char dow2[] PROGMEM = "Uto";
> char dow3[] PROGMEM = "Str";
> char dow4[] PROGMEM = "Stv";
> char dow5[] PROGMEM = "Pia";
> char dow6[] PROGMEM = "Sob";
>
> // Days of week in an array.
> PGM_P dow[] PROGMEM = { dow0, dow1, dow2, dow3, dow4, dow5, dow6 };
>
> // Time struct from BQ3285
> typedef struct {
> // time values
> uint8_t sec; // seconds (0..59)
> uint8_t min; // minutes (0..59)
> uint8_t hour; // hours (0..11, or 0..23 if BQ_HF is set in BQ_REG_B)
>
> // calendar values
> uint8_t dow; // day of week (1..7, 1 = Sunday)
> uint8_t day; // day of month (1..31)
> uint8_t month; // month (1..12)
> uint8_t year; // year (0..99)
> } bq_time_t;
>
> // current time
> volatile bq_time_t now;
>
> // ...
>
> /* called from interrupt handler */
> // write the day of week
> uint8_t k = 1;
> uint8_t l = now.dow;
> lcd_write_int16(k); lcd_putc(','); // outputs: 1
> lcd_write_int16(l); lcd_putc(','); // outputs: 1 (now.dow is
> inited to 1 outside)
> lcd_write_int16(k==l); lcd_putc(','); // outputs: 1 (as it should)
> lcd_write_int16(dow[k]); lcd_putc(','); // outputs: address in dow[1]
> in pgm. space
> lcd_write_int16(dow[l]); lcd_putc(','); // outputs: 0 (?!)
>
>
> Whenever I try to index the dow[] array using a value from now.dow, I
> get zero. This is all the more interesting, because the following
> block, albeit unreasonable, works just as advertised:
>
> switch (now.dow-1) {
> case 0: lcd_write_string_P(dow[0]); break;
> case 1: lcd_write_string_P(dow[1]); break;
> case 2: lcd_write_string_P(dow[2]); break;
> case 3: lcd_write_string_P(dow[3]); break;
> case 4: lcd_write_string_P(dow[4]); break;
> case 5: lcd_write_string_P(dow[5]); break;
> case 6: lcd_write_string_P(dow[6]); break;
> default: lcd_write_string_P(PSTR("???")); break;
> }
> // But this doesn't: lcd_write_string_P(dow[now.dow-1]);
>
>
> Any help would be more than appreciated.
>
> Thanks,
> Zoran
>
>
>
>
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