- Sat Apr 22, 2017 2:50 pm
#65146
NodeMCU 1.0 (V2 Amica) - Arduino 1.6.9 - OneWire 2.3.3
I'm using the OneWire library to read several DS18B20s on one IO in parasite power mode. Regardless of whether I use D2 or D4, I'm seeing some strange signal levels on the OneWire data bus after the "convert temperatures w/ parasite power" command. See the attached pics below. A 328P Arduino keeps it's IO HIGH after issuing the OneWire convert command whereas the ESP8266's IO drops to about 1/2 Vcc right after the convert cmd but not right after the "skip ROM" cmd. This drop causes the DS18B20s to falsely & consistently report a temperature of either 85.0 or 127.92 deg C. Also note the difference in timing (pulse low/high lengths) of the 328P vs ESP8266. I used the identical sketch on both micros.
I'm using the OneWire library to read several DS18B20s on one IO in parasite power mode. Regardless of whether I use D2 or D4, I'm seeing some strange signal levels on the OneWire data bus after the "convert temperatures w/ parasite power" command. See the attached pics below. A 328P Arduino keeps it's IO HIGH after issuing the OneWire convert command whereas the ESP8266's IO drops to about 1/2 Vcc right after the convert cmd but not right after the "skip ROM" cmd. This drop causes the DS18B20s to falsely & consistently report a temperature of either 85.0 or 127.92 deg C. Also note the difference in timing (pulse low/high lengths) of the 328P vs ESP8266. I used the identical sketch on both micros.
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