Hi everyone,
I tried i2c communication with p9_17 and p9_18 with /dev/i2c-0 and
/dev/i2c-1.
I got same error in both cases: Remote I/O error.
But my ioctl() function is working and i got '0' return value(success).
Now i am confused with pull up resistors. Is it necessary to pull up p9_17
and p9_18 line to Vdd?
I know that there is internal pull up resistors present in BBB. Is this not
available for two enabled i2c buses?
How to enable all the three i2c buses?
Can I choose i2c1 and i2c2 for communication?
When I connected my slave board to BBB(p9_17 and p9_18) and checked the
command 'i2cdetect -r 1'
I got :
root@beaglebone:~# i2cdetect -r 1
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-1 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n] y
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
for 'i2cdetect -r 0 ' i got
root@beaglebone:~# i2cdetect -r 0
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-0 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n] y
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: UU -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: UU -- -- -- -- -- -- --
I am waiting for your great opinions.
On Thursday, December 11, 2014 11:39:35 AM UTC+5:30, [email protected]
wrote:
>
> Hi,
>
> I am trying to read two bytes of data from a board(slave) using
> BBB(master) through i2c interface.
>
> I connected my board's SDA and SCL lines to P9_18 and P9_17 of BBB
> respectively.
>
> My code is
>
> #include <stdio.h>
> #include <errno.h>
> #include <string.h>
> #include <fcntl.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <linux/i2c-dev.h>
> #include <sys/ioctl.h>
>
>
> int main()
> {
> int fd,i;
> int addr = 0x43;
> char buffer[10] = {0};
>
> fd = open("/dev/i2c-1", O_RDWR); // opening i2c-1 file. returns a file
> descriptor used by read
> if(fd < 0)
> {
> printf("i2c failed to open\n");
> }
>
> if(ioctl(fd, I2C_SLAVE, addr) < 0)
> printf("failed to acquire bus\n");
>
> if(read(fd,buffer,2) != 2) //reading 2 bytes of data
> {
> printf("i2c read failed\n");
>
> }
> else
> {
> for(i=0;i<2;i++)
> printf("the data is %d \n",buffer[i]);
> }
>
>
> return 0;
> }
>
>
>
>
>
>
> I got output --- "i2c read failed"
>
> What is the problem in my code? Or any problem in hardware? When I checked
> the following command, I got output like
>
> root@beaglebone:~# i2cdetect -l
> i2c-0 i2c OMAP I2C adapter I2C adapter
> i2c-1 i2c OMAP I2C adapter I2C adapter
> root@beaglebone:~# ls -l /sys/bus/i2c/devices/i2c-*
> lrwxrwxrwx 1 root root 0 Jan 1 2000 /sys/bus/i2c/devices/i2c-0 ->
> ../../../devices/ocp.3/44e0b000.i2c/i2c-0
> lrwxrwxrwx 1 root root 0 Jan 1 2000 /sys/bus/i2c/devices/i2c-1 ->
> ../../../devices/ocp.3/4819c000.i2c/i2c-1
>
>
> Can anyone find problem? Please reply.
>
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