Hi Evan,

The "write" address IS the "slave" address.  Depending on the manufacturer and their terminology, you may need to bitshift by 1, but other than that they're one in the same.

See here for more info (under the heading Userland Programming):

If using the "write" address as the "slave" address doesn't work, try bitshifting right by 1 (0x40 becomes 0x20, 0x26 becomes 0x13, etc).


On 03/27/2013 06:23 PM, Evan wrote:
Hi all,

I am trying to communicate via i2c with an Adafruit 16-Channel 12-bit
PWM/Servo Driver. This device receives i2c input signals, then outputs
pulses to 16 pwm ports. The issue is that the manufacturer only includes
"write" addresses (depending on which solder jumpers are used). I have
working voltage level converters from 1.8V to 5V, and I have tried a variety
of combinations with the solder jumpers, but whenever I type "i2cdetect -y
-r 3" in the command window, no slave addresses from this device are shown.

Normally I would control the i2c with c code by opening the port with 'fh',
then ioctl(fh, I2C_SLAVE, slave_addr), then write(), but I cannot do this
with only a "write" address and no "slave" addresses.

Would you have any suggestions with communicating via i2c with only a
"write" address? Any help would be much appreciated. Thank you.


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