Hi Brandon,
I'm currently using mmap (in Python) to achieve register wide GPIO. I'm
concerned though, that the kernel still thinks it owns that memory and
might inadvertently write to it (for ex: if you forget to disable the
heartbeat trigger). Do you know of a way to disable the sysfs interface /
claim those pins as being in use so that you can safely manipulate the mmap
either through software or a device tree overlay?
Thanks for your help.
On Tuesday, July 29, 2014 3:09:08 PM UTC-4, Brandon I wrote:
>
> That's still one bit control. There's going to be some unknown time
> between the bits that will depend on cpu usage. For true 8 bit, you need to
> use mmap to get a pointer to the gpio control block and modify the
> registers directly.
> Each gpio block has 32 pins, and each gpio block has a set and clear
> register that's 32 bits wide, one bit for each pin. Setting a bit in the
> set register will set the pin. Setting a bit in the clear register will
> clear the pin. So, to set 8 pins at once, you would write the 8 bits to the
> set, then to clear all 8, you would write those 8 bits to the clear
> register. This will truly be "at once", at least to the capabilities of the
> hardware.
>
> Sysfs has some pretty absurd overhead, so you'll get a few hundred kHz at
> most. With the the register manipulation using mmap, you'll end up with ~4
> MHz for a toggle like that.
>
>
> On Sunday, July 27, 2014 4:09:56 AM UTC-7, kthab...@gmail.com wrote:
>>
>> /sys/class/gpio/export this driver file i have used.
>>
>> but this control only one bit. so, i try to 8bit control like this
>>
>> #include "bb_gpio.h"
>> #include <stdio.h>
>> #include <sys/time.h>
>> //#include <string.h>
>>
>> void main(void)
>> {
>> gpio_export(p9_11); gpio_export(p9_12);
>> gpio_export(p9_13); gpio_export(p9_14);
>> gpio_export(p9_15); gpio_export(p9_16);
>> gpio_export(p9_17); gpio_export(p9_18);
>>
>> gpio_direction(p9_11,out); gpio_direction(p9_12,out);
>> gpio_direction(p9_13,out); gpio_direction(p9_14,out);
>> gpio_direction(p9_15,out); gpio_direction(p9_16,out);
>> gpio_direction(p9_17,out); gpio_direction(p9_18,out);
>> while(1){
>> pin_write(p9_11,1); pin_write(p9_12,1);
>> pin_write(p9_13,1); pin_write(p9_14,1);
>> pin_write(p9_15,1); pin_write(p9_16,1);
>> pin_write(p9_17,1); pin_write(p9_18,1);
>> sleep(1);
>> pin_write(p9_11,0); pin_wirte(p9_12,0);
>> pin_write(p9_13,0); pin_wirte(p9_14,0);
>> pin_write(p9_15,0); pin_wirte(p9_16,0);
>> pin_write(p9_17,0); pin_wirte(p9_18,0);
>> sleep(1);
>> };
>> }
>>
>>
>> ================#include "bb_gpio.h"================
>>
>> #ifndef BB_GPIO_H_
>> #define BB_GPIO_H_
>>
>> #include <stdio.h>
>> #include <string.h>
>>
>> /********************************************
>> * BB_GPIO headerfile
>> * This file only used to gpio control
>> * other feature using device-tree-overlay
>> * when using GPIO, the pin work to MODE7
>> *=====formula======
>> * GPIO N1[N2]
>> * gpio_number = (32 x N1) + N2
>> *==================
>> *********************************************/
>>
>> #define out 1
>> #define in 0
>>
>> #define export_PATH "/sys/class/gpio/export"
>> #define value_PATH "/sys/class/gpio/gpio%d/value"
>> #define direction_PATH "/sys/class/gpio/gpio%d/direction"
>> #define unexport_PATH "/sys/class/gpio/unexport"
>>
>> //*********************P9***********************
>> #define p9_11 30
>> #define p9_12 60
>> #define p9_13 31
>> #define p9_14 50
>> #define p9_15 48
>> #define p9_16 51
>> #define p9_17 5
>> #define p9_18 4
>> //#define p9_19 13
>> //#define p9_20 12
>> #define p9_21 3
>> #define P9_22 2
>> #define p9_23 49
>> #define p9_24 15
>> #define p9_25 117
>> #define p9_26 14
>> #define p9_27 115
>> //#define p9_28 113
>> //#define p9_29 111
>> #define p9_30 112
>> //#define p9_31 110
>> #define p9_41 20
>> //#define p9_41 116
>> //#define p9_42 114
>> #define p9_42 7
>> //*********************************************
>>
>>
>> //*********************P8***********************
>> //*********************************************
>>
>>
>>
>> //******************function*********************
>> int gpio_export(int);
>> int gpio_unexport(int);
>> int gpio_direction(int, int);
>> int pin_write(int, int);
>> int pin_read(int);
>> //***********************************************
>>
>>
>> #endif /*BB_GPIO_*/
>>
>> int gpio_export(int gpio_number)
>> {
>> FILE* fp=0;
>>
>> if((fp = fopen(export_PATH,"w"))==NULL){
>> printf("Cannot open export file(>>%s).\n", export_PATH);
>> return -1;
>> }
>> fprintf(fp,"%d",gpio_number);
>> fclose(fp);
>> }
>>
>> int gpio_unexport(int gpio_number)
>> {
>> FILE* fp;
>>
>> if((fp = fopen(unexport_PATH,"w"))==NULL){
>> printf("Cannot open unexport file(>>%s).\n", unexport_PATH);
>> return -1;
>> }
>> fprintf(fp,"%d",gpio_number);
>> fclose(fp);
>> }
>>
>> int gpio_direction(int gpio_number,int direction)
>> {
>> FILE* fp;
>> char set_value[4]={0};
>> char dir_path[50]={0};
>> sprintf(dir_path, direction_PATH, gpio_number);
>> if((fp = fopen(dir_path,"w"))==NULL){
>> printf("Cannot open direction file(>>%s).\n",dir_path);
>> return -1;
>> }
>> rewind(fp);
>> if(direction == out){
>> strcpy(set_value,"out");
>> fwrite(&set_value,sizeof(char),3,fp);
>> fclose(fp);
>> } else if(direction == in){
>> strcpy(set_value,"in");
>> fwrite(&set_value,sizeof(char),2,fp);
>> fclose(fp);
>> } else{
>> printf("invalue pin mode(%d)\n",direction);
>> return -1;
>> }
>> fclose(fp);
>> return 1;
>> }
>>
>> int pin_write(int gpio_number,int value)
>> {
>> FILE* fp;
>> char val_path[50]={0};
>> char set_value[2]={0};
>>
>> sprintf(val_path, value_PATH, gpio_number);
>> if((fp = fopen(val_path,"w"))==NULL){
>> printf("Cannot open value file(>>%s).\n",val_path);
>> return -1;
>> }
>>
>> rewind(fp);
>> if(value == 1){
>> strcpy(set_value,"1");
>> }
>> else if(value == 0){
>> strcpy(set_value,"0");
>> }
>> else {
>> printf("invalid value pin(%d)(%d)\n", gpio_number, value);
>> return -1;
>> }
>>
>> fwrite(&set_value, sizeof(char), 1, fp);
>> fclose(fp);
>> return 0;
>> }
>>
>> int pin_read(int gpio_number)
>> {
>> FILE* fp;
>> int value=0;
>> char val_path[50]={0};
>>
>> sprintf(val_path, value_PATH, gpio_number);
>> if((fp = fopen(val_path,"r"))==NULL){
>> printf("Cannot open value file(>>%s).\n",val_path);
>> return -1;
>> }
>>
>> rewind(fp);
>> value = fgetc(fp) - '0';
>> fclose(fp);
>> return value;
>> }
>>
>>
>>
>>
>> but compile error...
>>
>> root@beaglebone:/home/debian/workspace/sources/gpio_control# \
>> > gcc -o led_blink led_blink.c
>> /tmp/ccfrwmlk.o: In function `main':
>> led_blink.c:(.text+0x5c8): undefined reference to `pin_wirte'
>> led_blink.c:(.text+0x5e0): undefined reference to `pin_wirte'
>> led_blink.c:(.text+0x5f8): undefined reference to `pin_wirte'
>> led_blink.c:(.text+0x610): undefined reference to `pin_wirte'
>> collect2: ld returned 1 exit status
>> root@beaglebone:/home/debian/workspace/sources/gpio_control#
>>
>> i don't know why .. help please
>>
>
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