User manual

1-Wire Application Guide v1.04 Page 14 of 41
and the connections between the serial port and TEMP08. See the Trouble-
shooting PC Problems section later in this manual for other considerations.
Issue a TMP command now and make sure that the on-board 1-Wire sensor is
reporting back correctly. If it is, proceed to the next steps. If it is not, then
something may have damaged the 1-Wire interface to TEMP08 and it may have
become defective. Return to Midon Design for repair, if necessary.
Now, connect one branch of your star network at a time to TEMP08. If you are
using a simple bus network, go ahead and re-connect it. Were there any
problems? If so, physically disconnect, one at a time, any sensors that indicate
error readings. Have the problems gone away when any one sensor is
disconnected? If so, disconnect all sensors again and then reconnect that one
sensor directly to TEMP08 with a short piece of cable. Does the sensor still give
a problem? If so, you have a defective sensor. If not, there is a wiring problem
to the original location of that sensor: fix it before proceeding. Don’t forget to
check for power wiring problems!
TEMP08 will report a short on the 1-Wire bus by issuing a “OW Bus Error”
message. If you see that at any time in this process, then consider the possibility
that a sensor is installed “backwards”; in other words, DQ and Ground are
reversed for that sensor. Also, consider the possibility that a short does exist in
your wiring, OR, although highly unlikely, a sensor has become completely
defective and is shorting out the bus.
Follow the above steps for all branches of your network.
If the steps above did not resolve the problem, and you are running a star
network, the problem might be a result of reflections. If you do not have 100-
Ohm resistors in the branch feeds, now would be a good time to insert them and
re-test your set-up.
If everything is now working, close HyperTerminal and restart your PC software.
If there are no problems, wonderful! If you are still having problems, report them
to the author of your PC software.