Use with a little care - read the i2cdetect man page
root@beaglebone:/home/debian/bin# i2cdetect -y -r 2
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- 18 -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
See: /usr/include/linux/i2c.h for i2c_msg structure and flags and i2c_rdwr_ioctl_data
* Module...: seeed_dip6.c
* Version..: 0.1 (Beta - unfinished)
* Author...: Henrik Thomsen/Mercantec <[email protected]
* Date.....: 10. nov 2023
*
* Abstract.: Implementation of Seeed Grove Sensor "I2C High
* Accuracy Temperature sensor" based on MCP-9808
* Implementet in user space using libi2c
* Mod. log.: 01-06-2021: Could not compile. Got i2c_smbus_read_word_data undefined.
Include <i2c/smbus.h> should be include. (Worked in 2020)
* License..: Free open software but WITHOUT ANY WARRANTY.
* Terms....: see <http://www.gnu.org/licenses>
*
* Documentation - see <https://mars.merhot.dk/w/index.php/Grove_I2C_High_Accuracy_Temerature_Sensor_-_Seeed>
*
* REMEMBER: Install the libi2c-dev package to compile this file
* Compile this example with: gcc seeed_dip6.c -o seeed_dip6 -li2c
*/
#include <stdio.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/ioctl.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
//Device specific information. (Perhaps better as command options or config file)
#define I2C_BUS "/dev/i2c-2"
#define I2C_ADDR 0x03 // Grove DIP-switch 6 slave address default
int main(void) {
int file;
int nmsgs_sent;
unsigned int len;
int i;
char buf[2][20];
struct i2c_msg msgs[I2C_RDRW_IOCTL_MAX_MSGS]; // I2C_RDRW_IOCTL_MAX_MSGS defined in linx/i2c-dev.h
struct i2c_rdwr_ioctl_data rdwr;
// init msgs's
for (i = 0; i < I2C_RDRW_IOCTL_MAX_MSGS; i++)
msgs[i].buf = NULL;
// Maybe errer just assumes bus number
file = open(I2C_BUS, O_RDWR);
if (file < 0) { // If error
fprintf(stderr, "ERROR: opening %s - %s\\n", I2C_BUS, strerror(errno));
exit(1);
}
if (file < 0)
fprintf(stderr, "ERROR: open_i2c_dev failed: %s", strerror(errno));
// Build IOCTL operation message structure. (What you want to do)
//msgs[0] Write one byte - Command in buf[0] - flags 0 = write
msgs[0].addr = I2C_ADDR;
msgs[0].flags = 0;
msgs[0].len = 1;
msgs[0].buf = buf[0];
buf[0][0] = 0x01;
//msgs[1] read 10 bytes to buf
msgs[1].addr = I2C_ADDR;
msgs[1].flags = 1;
msgs[1].len = 10;
msgs[1].buf = buf[1];
rdwr.msgs = msgs;
rdwr.nmsgs = 2;
nmsgs_sent = ioctl(file, I2C_RDWR, & rdwr);
if (nmsgs_sent != 2) {
fprintf(stderr, "ERRORi in line %d: Wrong number of messages: %d\\n", __LINE__, nmsgs_sent);
exit(0);
}
for (i = 0; i < 10; i++)
printf("Read 0x2d: %x\\n", buf[1][i]);
return (0);
}