Thanks both Tschmidt and CAI_Support for their suggestion and explanation, it totally makes sense.
My board was mounted in basement, is about 3-4 ft from noise sources, such as house furnace, a freezer and a dehumidifier. All 8 digital Inputs were connected to Noise Suppressor DLP-20-6V15 before connecting to board Inputs. I copied this practice from the posting by
W0VHA on
http://cocoontech.com/forums/topic/24741-board-locks-up-or-resets/ , hoping it would solve my problem when I was struggling with board reset. I did not notice any improvement, but would guess it probably eliminates some noises on the input lines that were not as severe as on 1-wire bus. My input lines are 30-40ft long CAT5 cable from basement to garage.
The humidity senor has a very short cable, 3 temp sensors are daisy chained on an old telephone cable, ~20 ft long, 1 monitors furnace intake, 1 for furnace exit, and 1 for main floor. So, in my system, the 1-wire cable is the closest to noise source, also it is probably most vulnerable one based on CAI_Support's explanation of directly connecting to CPU input pin.
I tested Tschmidt's suggestion on running temp sensors through DLP-20-6V15 noise suppressor, did not see any improvement, maybe its clamping voltage is still too high, or my environment is too noisy, or the temp sensor cable is too long. I tested a single temp sensor on a very short cable, 3-4 ft long, the board is running fine.
I think I can live with this problem for now, as long as I know where it is. When I get time, plan to use 2nd board for temperature monitoring, plus do some experiments on different cables and sensor locations, maybe test the idea of adding
5V transzob diode between 1-wire signal and ground. Will report back.
Niandong Liu