我写入后尝试从I2C总线上的存储单元读取一个值.当我在终端中运行它时,我得到奇怪的输出.
这是我的计划
#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;
}
The output from the program looks like this
Successful write
Successful read ��
在我的终端上,这些街区看起来更像钻石内的问号.我不确定在ASCII中对应什么.
为什么我不读回0x10,这是我最初写入的地址字节后的第二个字节？
根据第一组答案,这里是更新的代码：
#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addr时,无论argv [2]是什么,我都会得到FF,FF,FF作为输出.以下是设备树文件的适用部分.请注意,这是模拟的,所以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>;
};
};
};
};
以下是几个示例测试
尝试测试SiLabs时钟发生器
root@plnx_arm:~# /usr/bin/i2c-test-mem-location 0x54 0x00
Value of addr is: 84
Value of reg_addr is: 0
Unable to open device as slave
Device or resource busy
尝试测试eeprom设备
root@plnx_arm:~# /usr/bin/i2c-test-mem-location 0x5d 0x00
Value of addr is: 93
Value of reg_addr is: 0
Unable to open device as slave
Device or resource busy
这是我的第三次尝试的程序.在记下答案中的笔记之后,我写了这篇文章
#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,即便如此,我也遇到了同样的错误.
root@plnx_arm:~# /usr/bin/i2c-test-mem-location 0x00 0x10
The device address on the bus: 84Value of register address: 0
value to write is: 16
Unable to open device as slave
Device or resource busy
root@plnx_arm:~# /usr/bin/i2c-test-mem-location 0x30 0x10
The device address on the bus: 84Value of register address: 48
value to write is: 16
Unable to open device as slave
Device or resource busy
解决方法:
编辑2：我认为你可能没有正确设置你的I2C设备地址.您拥有的I2C_ADAPTER(“/ dev / i2c-0”)表示设备所在的I2C总线.您甚至没有使用I2C_DEVICE宏,但这应该是您应该传递给ioctl调用的内容(例如ioctl(文件,I2C_SLAVE,I2C_DEVICE);)它应该是您要访问的设备的I2C地址(例如0x5D)对于时钟发生器而不是0x00.
我也认为你的读/写不正确.一旦你通过open()和ioctl()指定了总线和设备,你就不用再担心了.您只需要担心要访问的寄存器(如果您的I2C设备使用寄存器)和实际数据.
要写入I2C设备,假设它使用一个字节的寄存器,写入两个字节的缓冲区：第一个是寄存器,第二个是要写入的值：
bool i2cdev_byte_write(int file, uint8_t reg, uint8_t val)
{
uint8_t bytes[2];
bytes[0] = reg;
bytes[1] = val;
/* Write the register followed by the value */
if (write(file, bytes, 2) != 2)
return false;
return true;
}
要从I2C设备读取,假设它使用一个字节的寄存器,写入一个字节的缓冲区(寄存器地址),然后读取一个或多个字节的缓冲区(该寄存器和后续寄存器的值)：
bool i2cdev_bytes_read(int file, uint8_t reg, unsigned int count, uint8_t *out_buf)
{
if (!out_buf)
return false;
/* Write the register */
if (write(file, ®, 1) != 1)
{
printf("Failed to write register value\n");
return false;
}
/* Read the specified number of bytes */
if (read(file, out_buf, count) != count)
{
printf("Failed to read from the i2c bus\n");
return false;
}
return true;
}
再次注意,上述所有注释都取决于它是使用单字节寄存器地址的I2C器件,并且它支持在一次读取多个字节时自动递增寄存器地址.您需要检查I2C设备的数据表,以确切地确定它是如何被访问的.
编辑：这是一个printf()新手失败.你不能只尝试printf一个字节数组.这不是printf()的工作原理.
试试这个：
printf("Buf = [%02X,%02X]\n", buf[0], buf[1]);
另外,正如我在原始响应中所写的那样,在读取寄存器内容之前,您可能需要再次将寄存器地址写回.