Android 9 读写eeprom at24c256
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2022-07-02 11:50:33
Android 9 读写eeprom at24c256linux 读取eeprom相对来说比较简单,因为内核中集成了大部分eeprom的驱动,文件目录在kernel/drivers/misc/eeprom/at24.c 。而且我们不用区分at24cxx的不同容量导致的读写方式不同,只要将at24.c编译到内核,然后dts中注册相应的i2c通道即可。手中的模块a0 a1 a2 都是接地,所以器件地址为0xa0,而dts中注册为七位地址,即0x50.&i2c1 {status = "okay"...
Android 9 读写eeprom at24c256
linux 读取eeprom相对来说比较简单,因为内核中集成了大部分eeprom的驱动,文件目录在kernel/drivers/misc/eeprom/at24.c 。
而且我们不用区分at24cxx的不同容量导致的读写方式不同,只要将at24.c编译到内核,然后dts中注册相应的i2c通道即可。手中的模块a0 a1 a2 都是接地,所以器件地址为0xa0,而dts中注册为七位地址,即0x50.
&i2c1 {
status = "okay";
clock-frequency = <300000>;
pinctrl-names="default";
pinctrl-0=<&i2c1_h_pins>;
at24c256@50{
compatible = "at24,24c256";
reg = <0x50>;
status = "okay";
};
};
按理说升级编译好的kernel后,就应该在对应的i2c节点下找到eeprom的节点,可是找来找去都没有找到这个节点,查看代码发现有这么个东西。
at24->nvmem_config.name = dev_name(&client->dev);
at24->nvmem_config.dev = &client->dev;
at24->nvmem_config.read_only = !writable;
at24->nvmem_config.root_only = true;
at24->nvmem_config.owner = THIS_MODULE;
at24->nvmem_config.compat = true;
at24->nvmem_config.base_dev = &client->dev;
at24->nvmem_config.reg_read = at24_read;
at24->nvmem_config.reg_write = at24_write;
at24->nvmem_config.priv = at24;
at24->nvmem_config.stride = 1;
at24->nvmem_config.word_size = 1;
at24->nvmem_config.size = chip.byte_len;
at24->nvmem = nvmem_register(&at24->nvmem_config);
if (IS_ERR(at24->nvmem)) {
err = PTR_ERR(at24->nvmem);
goto err_clients;
}
原来新的内核中引入了nvmem的架构对eeprom操作。重新配置内核,打开nvmem的编译选项,重新升级后,找到了nvmem的节点。
应用层对eeprom的操作,都是通过这个节点。
写个应用层代码:
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include "android/log.h"
#include <cutils/properties.h>
#include <stdbool.h>
#include <linux/input.h>
#define FILE_PATH "/sys/bus/nvmem/devices/1-00500/nvmem"
int main()
{
int fd;
int size;
char data[512] = {0};
char r_data[64] = {0};
char *w_data = "Hello World!Good Day!\n";
fd = open(FILE_PATH, O_RDWR);
if (fd < 0) {
printf("Can't open file %s\r\n", FILE_PATH);
return -1;
}
lseek(fd,0,SEEK_SET);
write(fd,data,sizeof(data)); //erase eeprom
lseek(fd,0,SEEK_SET);
write(fd,w_data,strlen(w_data));
lseek(fd,0,SEEK_SET);
size = read(fd,r_data,sizeof(r_data));
printf("read data==%s\n",r_data);
close(fd);
return 0;
}
Android.mk
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES:= max.c
LOCAL_MODULE := max
LOCAL_MODULE_TAGS := optional
LOCAL_SHARED_LIBRARIES += \
libcutils \
liblog
LOCAL_MODULE_PATH :=$(PRODUCT_OUT)/vendor/bin
include $(BUILD_EXECUTABLE)
运行结果如图
本文地址:https://blog.csdn.net/weixin_43932857/article/details/110622051