PIO

[Altera_Forum]

Hi all, 

 I&#39;m trying to write/read to and from some PIO. I have read as much as I can find about this topic on the forums and nios wiki but im not having much luck. Ive made a little test program:  <div class='codetop'>CODE</div><div class='codemain' style='height:200px;white-space:pre;overflow:auto'>#include <stdio.h># include <asm/io.h>  int main(void) { printf("writing to port:\n"); writew(0xFFFF,0x10402020); //data return 0; }</div>  where 0x10402020 is the address of my PIO. The code doesn&#39;t do anything really... ive tried a few other methods, none seemed to work. Can anyone help!?!?!?

[Altera_Forum]

You will need to bypass cache by turning on address bit 31. 

 writew(0xFFFF,0x10402020 | 0x80000000); //data  - Hippo

[Altera_Forum]

<div class='quotetop'>QUOTE (hippo @ Aug 7 2009, 10:54 AM) <{post_snapback}> (index.php?act=findpost&pid=23449)</div> 

--- Quote Start ---  You will need to bypass cache by turning on address bit 31.  writew(0xFFFF,0x10402020 | 0x80000000); //data  - Hippo[/b]  --- Quote End ---    Hi, what does that acually mean?   Unfortunately that didn&#39;t work. My output port are all set to high no matter what. Also, I have two ports, one output and one bidirectional. Is there a way to change the direction of a port? Or does writew /readw take care of that?

[Altera_Forum]

<div class='quotetop'>QUOTE (Gaz @ Aug 7 2009, 10:16 AM) <{post_snapback}> (index.php?act=findpost&pid=23448)</div> 

--- Quote Start ---  Hi all,  I&#39;m trying to write/read to and from some PIO. I have read as much as I can find about this topic on the forums and nios wiki but im not having much luck. Ive made a little test program:  <div class='codetop'>CODE  --- Quote End ---  <div class='codemain' style='height:200px;white-space:pre;overflow:auto'>#include <stdio.h># include <asm/io.h>  int main(void) { printf("writing to port:\n"); writew(0xFFFF,0x10402020); //data return 0; }</div>  where 0x10402020 is the address of my PIO. The code doesn&#39;t do anything really... ive tried a few other methods, none seemed to work. Can anyone help!?!?!?[/b]  --- Quote End ---     got it! had to find the correct register to change the direction (can find them in the nios2eds io.h). so doing utw(0xFFFF,(0x10402020+4)) wrote 0xFFFF to the direction register and changed the port to an output. Maybe this will help someone else one day....