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 >> > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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