我试图在写入后从 I2C 总线上的内存位置读取一个值。当我在终端中运行它时,我得到奇怪的输出。
这是我的程序
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
#define I2C_ADAPTER "/dev/i2c-0"
#define I2C_DEVICE 0x00
int main (int argc, char *argv[])
{
int file;
int addr = 0X00; /* XGPIOPS_DATA_LOW_OFFSET */
if((file = open(I2C_ADAPTER, O_RDWR)) < 0) {
printf("Failed to open the bus");
return -1;
}
if(ioctl(file, I2C_SLAVE, addr) < 0) {
printf("Unable to open device as slave %s", strerror(errno));
return -1;
}
char buf[10];
buf[0] = addr;
buf[1] = 0x10;
if(write(file, buf, 2) != 2) {
printf("Failed to write to bus %s.\n\n", strerror(errno));
}
else {
printf("Successful write\n");
printf(buf);
printf("\n\n");
}
if(read(file, buf, 2) != 2) {
printf("Failed to read from the i2c bus. %s\n\n", strerror(errno));
}
else {
printf("Successful read\n");
printf(buf);
printf("\n\n");
}
return 0;
}
程序的输出如下所示
写入成功
读取成功��
在我的终端上,这些块看起来更像是钻石内的问号。我不确定 ASCII 对应什么。
为什么我不读回 0x10,它是我最初写入的地址字节之后的第二个字节?
根据第一组答案,以下是更新后的代码:
#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
#define I2C_ADAPTER "/dev/i2c-0"
#define I2C_DEVICE 0x00
int main (int argc, char *argv[])
{
int file;
long addr, reg_addr;
char *end;
if(argc == 3) {
addr = strtol(argv[1], &end, 16);
printf("Value of addr is: %ld\n", addr);
reg_addr = strtol(argv[2], &end, 16);
printf("Value of reg_addr is: %ld\n", reg_addr);
}
else {
printf("arg failed\n\n.");
addr = 0x00;
}
if((file = open(I2C_ADAPTER, O_RDWR)) < 0) {
printf("Failed to open the bus\n");
return -1;
}
if(ioctl(file, I2C_SLAVE, addr) < 0) {
printf("Unable to open device as slave \n%s\n", strerror(errno));
return -1;
}
char buf[10];
buf[0] = addr;
buf[1] = reg_addr;
buf[2] = 0x10;
if(write(file, buf, 3) != 3) {
printf("Failed to write to bus %s.\n\n", strerror(errno));
}
else {
printf("Successful write\n");
printf(buf);
printf("\n\n");
}
if(read(file, buf, 3) != 3) {
printf("Failed to read from the i2c bus.\n %s\n\n", strerror(errno));
}
else {
printf("Successful read\n");
printf("Buf = [%02X,%02X,%02X]\n", buf[0], buf[1], buf[2]);
printf("\n\n");
}
return 0;
}
此时,每当我使用 0x00 作为地址时,无论 argv[2] 是什么,我都会得到 FF、FF、FF 作为输出。这是设备树文件的适用部分。请注意,这是模拟的,因此我无法探测物理设备。
&i2c0 {
status = "okay";
clock-frequency = <400000>;
pinctrl-names = "default";
i2cswitch@74 {
compatible = "nxp,pca9548";
#address-cells = <1>;
#size-cells = <0>;
reg = <0x74>;
i2c@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
si570: clock-generator@5d {
#clock-cells = <0>;
compatible = "silabs,si570";
temperature-stability = <50>;
reg = <0x5d>;
factory-fout = <156250000>;
clock-frequency = <148500000>;
};
};
i2c@2 {
#address-cells = <1>;
#size-cells = <0>;
reg = <2>;
eeprom@54 {
compatible = "at,24c08";
reg = <0x54>;
};
};
i2c@3 {
#address-cells = <1>;
#size-cells = <0>;
reg = <3>;
gpio@21 {
compatible = "ti,tca6416";
reg = <0x21>;
gpio-controller;
#gpio-cells = <2>;
};
};
i2c@4 {
#address-cells = <1>;
#size-cells = <0>;
reg = <4>;
rtc@51 {
compatible = "nxp,pcf8563";
reg = <0x51>;
};
};
i2c@7 {
#address-cells = <1>;
#size-cells = <0>;
reg = <7>;
hwmon@52 {
compatible = "ti,ucd9248";
reg = <52>;
};
hwmon@53 {
compatible = "ti,ucd9248";
reg = <53>;
};
hwmon@54 {
compatible = "ti,ucd9248";
reg = <54>;
};
};
};
};
这是几个测试示例
尝试测试 SiLabs 时钟发生器
root@plnx_arm:~# /usr/bin/i2c-test-mem-位置 0x54 0x00
地址的值为:84
reg_addr 的值为:0
无法将设备作为从属设备打开
设备或资源繁忙
尝试测试eeprom设备
root@plnx_arm:~# /usr/bin/i2c-test-mem-位置 0x5d 0x00
地址的值为:93
reg_addr 的值为:0
无法将设备作为从属设备打开
设备或资源繁忙
这是我第三次尝试的程序。考虑到答案中所做的笔记后,我写下了这个
#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
#define I2C_ADAPTER "/dev/i2c-0"
#define DEVICE_ADDRESS 0x54
int main (int argc, char *argv[])
{
int file;
uint8_t reg, value;
char *end;
printf("The device address on the bus: %d", DEVICE_ADDRESS);
if(argc == 3) {
reg = strtol(argv[1], &end, 16);
printf("Value of register address: %d\n", reg);
value = strtol(argv[2], &end, 16);
printf("value to write is: %d\n", value);
}
else {
printf("arg failed\n\n.");
}
if((file = open(I2C_ADAPTER, O_RDWR)) < 0) {
printf("Failed to open the bus\n");
return -1;
}
if(ioctl(file, I2C_SLAVE, DEVICE_ADDRESS) < 0) {
printf("Unable to open device as slave \n%s\n", strerror(errno));
return -1;
}
char buf[10];
buf[0] = reg;
buf[1] = value;
if(write(file, buf, 2) != 2) {
printf("Failed to write to bus %s.\n\n", strerror(errno));
}
else {
printf("Successful write\n");
printf(buf);
printf("\n\n");
}
if(read(file, buf, 2) != 2) {
printf("Failed to read from the i2c bus.\n %s\n\n", strerror(errno));
}
else {
printf("Successful read\n");
printf("Buf = [%02X,%02X,%02X]\n", buf[0], buf[1], buf[2]);
printf("\n\n");
}
return 0;
}
不幸的是,即使如此,我还是遇到了同样的错误。
root@plnx_arm:~# /usr/bin/i2c-test-mem-位置 0x00 0x10
总线上的设备地址:84 寄存器地址的值:0
要写入的值为:16
无法将设备作为从属设备打开
设备或资源繁忙
root@plnx_arm:~# /usr/bin/i2c-test-mem-位置 0x30 0x10
总线上的设备地址:84 寄存器地址的值:48
要写入的值为:16
无法将设备作为从属设备打开
设备或资源繁忙