LED no reaction after successfully loading lights.c into the cyclone II

Altera_Forum · ‎09-18-2009

Hi, guys,

Thank to the previous help from you, finally I managed to load the c program into the cyclone II using Altera Monitor Program without any error message....

The program is as follows:

#define switches (volatile char *) 0x0001800# define leds (char *) 0x0001810

void main()

{ while (1)

*leds = *switches;

}

it is supposed to "load the addresses of the Data registers in the two PIOs into processor registers r2 and r3. It then has an infinite loop that

merely transfers the data from the input PIO, Switches, to the output PIO, LEDs." according to the sopc introduction tutorial...

however, the no matter how i tilt the switches on the board, the LED never turns on!

How could this be?

Thanks and regards

Altera_Forum · ‎09-18-2009

Please grit, ask your questions in only one thread at a time. Either put all your questions in one thread, or create a new thread for each question, but do not post them in multiple places. It makes it very difficult to follow up.

What you are facing is probably a cache problem. The first time the CPU reads the switches value, it is put in its data cache. Then the other times the CPU will read the cached value instead of the one from the switches. One way to get around this is to uso the IORD/WR macros:

(not compiled/tested, but the basic idea is there)

#include <io.h>
# define SWITCHES 0x0001800
# define LEDS 0x0001810
void main()
{
  while (1)
    IOWR(LEDS,0,IORD(SWITCHES,0));
}

Or even better, to use the dedicated PIO macros:

#include "altera_avalon_pio_regs.h"
# define SWITCHES 0x0001800
# define LEDS 0x0001810
void main()
{
  while (1)
    IOWR_ALTERA_AVALON_PIO_DATA(LEDS,IORD_ALTERA_AVALON_PIO_DATA(SWITCHES));
}

Also check that the addresses that you put in the defines match the ones in your SOPC system. You should use the *_BASE constants that are automatically generated for you in system.h, it will same you some time and trouble.

Altera_Forum · ‎09-18-2009

--- Quote Start ---

Please grit, ask your questions in only one thread at a time. Either put all your questions in one thread, or create a new thread for each question, but do not post them in multiple places. It makes it very difficult to follow up.

What you are facing is probably a cache problem. The first time the CPU reads the switches value, it is put in its data cache. Then the other times the CPU will read the cached value instead of the one from the switches. One way to get around this is to uso the IORD/WR macros:

(not compiled/tested, but the basic idea is there)

#include <io.h>
# define SWITCHES 0x0001800# define LEDS 0x0001810
void main()
{
  while (1)
    IOWR(LEDS,0,IORD(SWITCHES,0));
}

Or even better, to use the dedicated PIO macros:

#include "altera_avalon_pio_regs.h"
# define SWITCHES 0x0001800# define LEDS 0x0001810
void main()
{
  while (1)
    IOWR_ALTERA_AVALON_PIO_DATA(LEDS,IORD_ALTERA_AVALON_PIO_DATA(SWITCHES));
}

Also check that the addresses that you put in the defines match the ones in your SOPC system. You should use the *_BASE constants that are automatically generated for you in system.h, it will same you some time and trouble.

--- Quote End ---

Hi, Daixiwen,

sorry about the thread posting...I will put all my questions in one post next time...

Your code works on my board! and the LEDs are now reacting accordingly.

Thanks a million!

Altera_Forum · ‎09-18-2009

@grit

the problems are due to the caching of the data. The information is only written in the cache and not forwarded to the IO. You could solve your problem either by adding the attribute "volatile" to your IO variable as such:

#define Switches (volatile char *) 0x0001800# define LEDs (volatile char *) 0x0001810
void main()
{ while (1)
*LEDs = *Switches;
}

or by following the suggestions by Daixiwen.

Hope this helps...

Altera_Forum · ‎09-18-2009