使用Linux上的I2C读/写 [英] Reading / writing from using I2C on Linux

问题描述

我试图读取/写入到连接在一个I2C总线上地址 FM24CL64-GTR FRAM 片 0B 1010 011 。

I'm trying to read/write to a FM24CL64-GTR FRAM chip that is connected over a I2C bus on address 0b 1010 011.

当我试着写3个字节（数据地址2个字节，+数据一个字节），我得到一个内核消息（ [12406.360000] I2C适配器I2C-0：sendbytes：NAK救助），以及写收益= 3，见code如下：

When I'm trying to write 3 bytes (data address 2 bytes, + data one byte), I get a kernel message ([12406.360000] i2c-adapter i2c-0: sendbytes: NAK bailout.), as well as the write returns != 3. See code below:

#include <linux/i2c-dev.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdint.h>

int file;
char filename[20];
int addr = 0x53; // 0b1010011; /* The I2C address */
uint16_t dataAddr = 0x1234;
uint8_t val = 0x5c;
uint8_t buf[3];

sprintf(filename,"/dev/i2c-%d",0);
if ((file = open(filename,O_RDWR)) < 0)
    exit(1);

if (ioctl(file,I2C_SLAVE,addr) < 0)
    exit(2);

buf[0] = dataAddr >> 8;
buf[1] = dataAddr & 0xff;
buf[2] = val;

if (write(file, buf, 3) != 3)
    exit(3);

...

然而，当我写2个字节，然后写另一个字节，我没有得到任何内核错误，而是试图从FRAM读的时候，我总是回来0.下面是code从FRAM阅读：

However when I write 2 bytes, then write another byte, I get no kernel error, but when trying to read from the FRAM, I always get back 0. Here is the code to read from the FRAM:

uint8_t val;

if ((file = open(filename,O_RDWR)) < 0)
    exit(1);

if (ioctl(file,I2C_SLAVE,addr) < 0)
    exit(2);

if (write(file, &dataAddr, 2) != 2) {
    exit(3);

if (read(file, &val, 1) != 1) {
    exit(3);

中的所有功能都返回错误值，而我也试了一下：

None of the functions return an error value, and I have also tried it with:

#include <linux/i2c.h>

struct i2c_rdwr_ioctl_data work_queue;
struct i2c_msg msg[2];
uint8_t ret;

work_queue.nmsgs = 2;
work_queue.msgs = msg;

work_queue.msgs[0].addr = addr;
work_queue.msgs[0].len = 2;
work_queue.msgs[0].flags = 0;
work_queue.msgs[0].buf = &dataAddr;

work_queue.msgs[1].addr = addr;
work_queue.msgs[1].len = 1;
work_queue.msgs[1].flags = I2C_M_RD;
work_queue.msgs[1].buf = &ret;

if (ioctl(file,I2C_RDWR,&work_queue) < 0)
    exit(3);

这也是成功，但总是返回0。这是否表明一个硬件问题，还是我做错了什么？

Which also succeeds, but always returns 0. Does this indicate a hardware issue, or am I doing something wrong?

是否有FM24CL64-GTR任何FRAM驱动程序通过I2C在Linux上，并且将这个API是什么？任何一个环节将是有益的。

Are there any FRAM drivers for FM24CL64-GTR over I2C on Linux, and what would the API be? Any link would be helpful.

推荐答案

在NAK是一个很大的提示：WriteProtect引脚被外部上拉，不得不被驱赶到地面后，该地址进行一次写其次是数据字节是成功的（第一个code段）。

The NAK was a big hint: the WriteProtect pin was externally pulled up, and had to be driven to ground, after that a single write of the address followed by data-bytes is successful (first code segment).

有关读出可以写出的地址的第一（使用写入（）），然后顺序数据可以被读取从该地址开始

For reading the address can be written out first (using write()), and then sequential data can be read starting from that address.

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