Показать сообщение отдельно
Старый 05.12.2007, 12:55   #7
Petr
Senior Member
 
Аватар для Petr
 
Регистрация: 25.02.2007
Возраст: 47
Сообщений: 1,734
Вес репутации: 3438/93
Petr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond reputePetr has a reputation beyond repute
По умолчанию Так я так и не понял. Вы доку то читали или нет ? (+)

А именно вот это место:

In parasite power mode, the 1-wire bus and C
PP can provide sufficient current to the DS18S20 for most
operations as long as the specified timing and voltage requirements are met (refer to the DC
ELECTRICAL CHARACTERISTICS and the AC ELECTRICAL CHARACTERISTICS sections of this
data sheet). However, when the DS18S20 is performing temperature conversions or copying data from
the scratchpad memory to EEPROM, the operating current can be as high as 1.5 mA. This current can
cause an unacceptable voltage drop across the weak 1-wire pullup resistor and is more current than can be
supplied by C
PP. To assure that the DS18S20 has sufficient supply current, it is necessary to provide a
strong pullup on the 1-wire bus whenever temperature conversions are taking place or data is being
copied from the scratchpad to EEPROM. This can be accomplished by using a MOSFET to pull the bus
directly to the rail as shown in Figure 4. The 1-wire bus must be switched to the strong pullup within 10
s (max) after a Convert T [44h] or Copy Scratchpad [48h] command is issued, and the bus must be held
high by the pullup for the duration of the conversion (t
conv) or data transfer (twr = 10 ms). No other
activity can take place on the 1-wire bus while the pullup is enabled.

Это я к тому, что адаптер делает этот самый стронг пулап
а Ваш контроллер нет (похоже на то)

Petr вне форума   Ответить с цитированием