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POwrite()ing to i2c device: Operation not permitted
 

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  1. POwrite()ing to i2c device: Operation not permitted
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    <p>So I have 2 PCA9555 (16 channel digital I/O) chips connected to a small embedded device running Linux over i2c. The PCA9555 devices have 7 bit addresses 0100000 and 0100001.</p> <p>When I power up the board, I run:</p> <pre><code># modprobe i2c-i801 # modprobe i2c-dev # i2cdetect -l i2c-0 smbus SMBus I801 adapter at 0500 SMBus adapter # i2cdump -y -r 0 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- ... (Same for every line) 70: -- -- -- -- -- -- -- # dmesg|tail i801_smbus 0000:00:1f.3 Transaction timeout ... (For every '--' in i2cdump, one of these errors outputted) i801_smbus 0000:00:1f.3 Transaction timeout </code></pre> <p>So then I tried to write a simple program to set all pins on the first PCA9555 chip to output high:</p> <pre><code>char *file; unsigned char buf[3]; int addr, fd; file = "/dev/i2c-0"; addr = 0x20; /* 0100000 */ if((fd = open(file, O_RDWR)) &lt; 0){ err(1, "open()"); } if(ioctl(fd, I2C_SLAVE, addr) &lt; 0){ /* also tried I2C_SLAVE_FORCE */ err(1, "ioctl()"); } /* Set all digital I/Os to output */ buf[0] = 6; buf[1] = 0x00; buf[2] = 0x00; if(write(fd, buf, 3) != 3){ err(1, "write() 1"); } /* Set all outputs high */ buf[0] = 2; buf[1] = 0xFF; buf[2] = 0xFF; if(write(fd, buf, 3) != 3){ err(1, "write() 2"); } return 0; </code></pre> <p>Running this returns:</p> <pre><code># ./i2c ./i2c: write() 1: Operation not supported </code></pre> <p>So I don't really understand what I'm doing wrong. Assuming the hardware is wired correctly where do I go from here?</p>
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    1. PTQuestion
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    1. USRyan
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      1. POwrite()ing to i2c device: Operation not permitted
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      1. VTUpMod
    1. COanything in `dmesg` from the i2c-core?
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      1. POwrite()ing to i2c device: Operation not permitted
      1. USWill Tate
    2. CONope, nothing from i2c-core. Is i2c-core a module? Because I don't see it listed in /lib/modules
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      1. POwrite()ing to i2c device: Operation not permitted
      1. USRyan
 

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