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Usage of an external library (bcm2835) with halcompile
- tommylight
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7 years 3 months ago #140551
by wicki
Replied by wicki on topic Usage of an external library (bcm2835) with halcompile
My plan was to set a GPIO-pin before sending the eth-packet.
I have bypassed the problem by direct IO (see below - shamelessly stolen from here: www.pieter-jan.com/node/15 ).
Now I can measure the time difference between send and reaction to the reception.
The last image here is the result.
erste.de/timing-tests.PI4.html
license "GPL";
;;
#define BCM2708_PERI_BASE 0xfe000000 /* 0x20000000 */
#define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
#define PIN 22 // GPIO3 // 27 GPIO2 17 // GPIO0
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#define PAGE_SIZE (4*1024)
#define BLOCK_SIZE (4*1024)
int mem_fd;
void *gpio_map;
// I/O access
volatile unsigned *gpio;
// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define OUT_GPIO(g) *(gpio+((g)/10)) |= (1<<(((g)%10)*3))
#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<
?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
#define GPIO_SET *(gpio+7) // sets bits which are 1 ignores bits which are 0
#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
void flash() {
int f1=0;
GPIO_CLR = (1 << PIN);
GPIO_SET = (1 << PIN);
usleep(1);
GPIO_CLR = (1 << PIN);
return;
}
//
// Set up a memory regions to access GPIO
//
void setup_io()
{
/* open /dev/mem */
if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
printf("can't open /dev/mem \n");
exit(-1);
}
/* mmap GPIO */
gpio_map = mmap(
NULL, //Any adddress in our space will do
BLOCK_SIZE, //Map length
PROT_READ|PROT_WRITE, // Enable reading & writting to mapped memory
MAP_SHARED, //Shared with other processes
mem_fd, //File to map
GPIO_BASE //Offset to GPIO peripheral
);
close(mem_fd); //No need to keep mem_fd open after mmap
if (gpio_map == MAP_FAILED) {
printf("mmap error %d\n", (int)gpio_map); //errno also set!
exit(-1);
}
// Always use volatile pointer!
gpio = (volatile unsigned *)gpio_map;
int g,rep;
// Set up gpi pointer for direct register access
INP_GPIO(PIN); // must use INP_GPIO before we can use OUT_GPIO
OUT_GPIO(PIN);
return;
} // setup_io
I have bypassed the problem by direct IO (see below - shamelessly stolen from here: www.pieter-jan.com/node/15 ).
Now I can measure the time difference between send and reaction to the reception.
The last image here is the result.
erste.de/timing-tests.PI4.html
license "GPL";
;;
#define BCM2708_PERI_BASE 0xfe000000 /* 0x20000000 */
#define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
#define PIN 22 // GPIO3 // 27 GPIO2 17 // GPIO0
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#define PAGE_SIZE (4*1024)
#define BLOCK_SIZE (4*1024)
int mem_fd;
void *gpio_map;
// I/O access
volatile unsigned *gpio;
// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define OUT_GPIO(g) *(gpio+((g)/10)) |= (1<<(((g)%10)*3))
#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<
?(a)+4:(a)==4?3:2)<<(((g)%10)*3))#define GPIO_SET *(gpio+7) // sets bits which are 1 ignores bits which are 0
#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
void flash() {
int f1=0;
GPIO_CLR = (1 << PIN);
GPIO_SET = (1 << PIN);
usleep(1);
GPIO_CLR = (1 << PIN);
return;
}
//
// Set up a memory regions to access GPIO
//
void setup_io()
{
/* open /dev/mem */
if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
printf("can't open /dev/mem \n");
exit(-1);
}
/* mmap GPIO */
gpio_map = mmap(
NULL, //Any adddress in our space will do
BLOCK_SIZE, //Map length
PROT_READ|PROT_WRITE, // Enable reading & writting to mapped memory
MAP_SHARED, //Shared with other processes
mem_fd, //File to map
GPIO_BASE //Offset to GPIO peripheral
);
close(mem_fd); //No need to keep mem_fd open after mmap
if (gpio_map == MAP_FAILED) {
printf("mmap error %d\n", (int)gpio_map); //errno also set!
exit(-1);
}
// Always use volatile pointer!
gpio = (volatile unsigned *)gpio_map;
int g,rep;
// Set up gpi pointer for direct register access
INP_GPIO(PIN); // must use INP_GPIO before we can use OUT_GPIO
OUT_GPIO(PIN);
return;
} // setup_io
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