I am trying to use I2C parts on a house monitoring network and am having
a problem. I am looking for a way to detect whether an address is present or
not on the network, since there is the possiblity for a device to be
disconnected. I decided to use the ack part of the I2C frame to detect
whether a device is present, thinking that without a device being present
the ack wouldn't be received. According to the NS LM75 data sheet (one of
the devices I am using) the device sends an ack (by making SDA low) right
after the address byte is sent, unfortunately this is always returned as a 0
(ack accepted) whether or not a device is present. I don't understand how
this could be, do other devices on the network send the ack even if they are
not being addressed?? Has anyone sucessfully detected the ack sent by the
LM75 (or other I2C device)? Am I understanding the concept of an ack
properly? Just as an addition, I have made sure that the master is high
during this time that ack should be sent. Thank you for any help. TTYL