[Gumstix-users] Direct register access control of GPIO ARM interface on Overo Water +TOBI - SOLVED

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This is one way for direct-register access control of the GPIO ARM interface
of the Gumstix Overo Water.
I mounted the Gumstix on a TOBI board for connections. I obtained to control
the gpio_186 digital pin.
The procedure can be easily extended to the other digital pins. I haven't
recompiled the kernel or touched the setup files or 
the pre-existing drivers... nothing of this.
This is my recipe:
1) install on a formatted SD card the stable Gumstix armstrong linux version
( see http://gumstix.org/get-started/how-to.html )
2) connect your Overo Water + Tobi system on Internet by LAN cable
3) connect the Gumstix to your windows PC by the USB cable and by the
software putty.exe, open a control windows
   selecting an emulated serial connection (see putty instructions)
3) Check the internet link, use ( on the Gumstix )
   ifconfig eth1 192.168.0.5 netmask 255.255.255.0
 or whatever the desired IP address+netmask for connecting the Gumstix @
your router    
4) install the C cross compiler :
   $ echo 'src/gz angstrom-base
http://www.angstrom-distribution.org/feeds/unstable/ipk/glibc/armv7a/base' 
> /etc/opkg/angstrom-base.conf
   $ opkg update
   $ opkg install task-native-sdk
 or better use
   $ opkg update
   $ opkg install task-native-sdk
 for updating all the software.
5) Reboot the gustix
6) Put the following code on your home directory ( or wherewer you prefer )
editing it with 
   VI main.c
 or with any other any other editor you like. I use normally Eclipse for
editing my software on the PC and transferring
 it to the remote system (the Gumstix) ( contact me if you want more info on
this); 
 call the file "main.c"

/****************************************************************************************
                             LOCAL INCLUDES DEFINITION

****************************************************************************************/
#include <stdio.h>  
#include "init_mem.h"
#include "init_SPI_1.h"
#include <fcntl.h>      //ok for mmap param
#include <sys/mman.h>   //ok for mmap
/****************************************************************************************
                             LOCAL PARAMETERS DEFINITION

****************************************************************************************/
#define SCM_INTERFACE_BASE 0x48002000
#define SCM_PADCONFS_BASE 0x48002030
#define CONTROL_PADCONF_SYS_NIRQ (*(volatile unsigned long *)0x480021E0)
#define CONTROL_PADCONF_SYS_NIRQ_OFFSET 0x1B0

#define GPIO6_BASE 0x49058000
#define GPIO6_SYSCONFIG_OFFSET 0x10
#define GPIO6_CLEARDATAOUT_OFFSET 0x90
#define GPIO6_SETDATAOUT_OFFSET 0x94
#define GPIO6_OE_OFFSET 0x34
#define GPIO6_CTRL_OFFSET 0x30

#define MAP_SIZE (volatile unsigned long) 4*1024
#define MAP_MASK (volatile unsigned long)( MAP_SIZE - 1 )
/****************************************************************************************
                             COMMON VARIABLES DEFINITION

****************************************************************************************/
#define u32 volatile unsigned long
u32 *A;
u32 *B;
/****************************************************************************************
                             LOCAL FUNCTIONS DEFINITION

****************************************************************************************/

/****************************************************************************************
  Function name:     int main(void)
  Last modification: 04/08/2012
  Version:           1.10
  Notes:

****************************************************************************************/
int main(void){
unsigned long i;
int fd;
printf("\n\n\n\n\n\n\n");
printf("\n\n");
printf("   ------------------------------------------\n");
printf("   |               SPI Sample                |\n");
printf("   ------------------------------------------\n");
printf("   |   Direct Register Access GPIO           |\n");
printf("   ------------------------------------------\n");
printf("Base address  GPIO6: 0x%04x\n",(GPIO6_BASE ));// OK
printf("\n");

fd = open("/dev/mem", O_RDWR | O_SYNC);
if (fd < 0) {printf("Could not open file\n"); return;}
A = (u32 *) mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd,
SCM_INTERFACE_BASE & ~MAP_MASK); 
 if (A == MAP_FAILED) {printf("Mapping failed    value 0x%04x\n",A);
close(fd); return;} // %d.\n
 if (A<=0) {printf("Mapping failed\n"); close(fd); return;}
 printf("SCM_SCM_BASE 0x%08x\n",SCM_INTERFACE_BASE);
 printf("SCM_PADCONFS_BASE 0x%08x\n",SCM_INTERFACE_BASE+0x30);
 printf("SCM_PADCONFS offset 0x%08x\n",CONTROL_PADCONF_SYS_NIRQ_OFFSET);
 printf("Pointer: 0x%08x\n",(u32) A);
 printf("Pointer+offset:
0x%08x\n",(u32)A+0x30+CONTROL_PADCONF_SYS_NIRQ_OFFSET );
 printf("Pointer+offset content: 0x%08x\n",*(u32
*)((u32)A+0x30+CONTROL_PADCONF_SYS_NIRQ_OFFSET) );
 *(u32 *)((u32)A+0x30+CONTROL_PADCONF_SYS_NIRQ_OFFSET)|=(0b100<<16); //
imposta mode 4 sul registro configurazione pad 186; abilita uso pin digitale
 close(fd);
 printf("PAD configuration done.\n",MAP_SIZE);
/************************************************/

fd = open("/dev/mem", O_RDWR | O_SYNC);
if (fd < 0) {printf("Could not open file\n"); return;}
B = (volatile unsigned long*) mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, GPIO6_BASE & ~MAP_MASK); // COM1 0x4806A000
  if (B == MAP_FAILED) {printf("Mapping failed    value 0x%04x\n",B);
close(fd); return;} // %d.\n
  if (B<=0) {printf("Mapping failed\n"); close(fd); return;}

  printf("Map_Size: 0x%08x     ",MAP_SIZE);
  printf("Map_Mask: 0x%08x     ",MAP_MASK);
  printf("Map_Mask: Reverse 0x%08x\n",~MAP_MASK);
  printf("Base address: 0x%08x     ",(GPIO6_BASE & ~MAP_MASK));
  printf("Offset: 0x%08x     ",GPIO6_CTRL_OFFSET);
  printf("Base address+offset: 0x%08x\n",(GPIO6_BASE +GPIO6_CTRL_OFFSET));
  printf("Pointer: 0x%08x\n",(u32)B);

// gpio_186 handling
 printf("Pointer+offset: 0x%08x     ",(u32)B+(GPIO6_SYSCONFIG_OFFSET));
 printf("Pointer+offset content: 0x%08x     ",*(u32
*)((u32)B+GPIO6_SYSCONFIG_OFFSET));
 *(u32 *)((u32)B+GPIO6_SYSCONFIG_OFFSET)|= 0x00000004;// bit2=1 enable/wake
up, free running  clock
 printf("Pointer+offset content: 0x%08x\n",*(u32
*)((u32)B+GPIO6_SYSCONFIG_OFFSET));
 printf("***\n");
   printf("Pointer+offset: 0x%08x     ",(u32)B+(GPIO6_CTRL_OFFSET));
   printf("Pointer+offset content: 0x%08x     ",*(u32
*)((u32)B+GPIO6_CTRL_OFFSET));
   *(u32 *)((u32)B+GPIO6_CTRL_OFFSET)&= 0xfffffffe;  // bit0=0 module
enabled, clock not gated , clock=interface clock divided by 8
   //*(u32 *)((u32)B+GPIO6_CTRL_OFFSET)&= 0xfffffff8;  //
bit0=0,bit1=0,bit2=0 module enabled, clock not gated , clock=interface clock
not divided
   printf("Pointer+offset content mod: 0x%08x\n",*(u32
*)((u32)B+GPIO6_CTRL_OFFSET));
   printf("***\n");
 printf("Pointer+offset: 0x%08x     ",(u32)B+(GPIO6_OE_OFFSET));
 printf("Pointer+offset content: 0x%08x     ",*(u32
*)((u32)B+GPIO6_OE_OFFSET));
 *(u32 *)((u32)B+GPIO6_OE_OFFSET)&= 0xfbffffff;  // bit26=0, gpio_186 output
 printf("Pointer+offset content mod: 0x%08x\n",*(u32
*)((u32)B+GPIO6_OE_OFFSET));
 printf("***\n");
// generate a pulse stream on gpio_186 pin output
for (i=0;i<100000;i++){
	*(u32 *)((u32)B+(GPIO6_CLEARDATAOUT_OFFSET))|= 0x04000000;
	*(u32 *)((u32)B+(GPIO6_SETDATAOUT_OFFSET))  |= 0x04000000;
 }
close(fd);
printf("pointers to memory are ok\n") ;
return(0);
}// eof

7) compile the file "main.c" you have just created with
 gcc -o main main.c
8) execute the compiled file
 ./main
 and you'll see on gpio-186 ( on the TOBI board, the pin 17) the square
waveform of 1.8Vpp.
 See

http://www.gumstix.org/hardware-design/overo-coms/74-overo-connectors/97-gumstix-overo-series-40-pin-header.html
 for the TOBI connector pinout.
 That's all!
 PS Thanks to Dave Hylands for the advices.

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