Why argue with me and make me explain it numerous times when you could have just looked at the picture and understood
I got your point the first time but you don't seem to have figured that out.
I was asking questions not directly relevant to your post, not trying to have an argument nor to hear that I didn't get your point.. again and again and again. You are wrong. I understood the first explanation. And given that yes, I did question the absolute world-enlightening brilliance of parasite mode over using a grody little power wire instead, I should be flayed alive and fed to ants.
At 20 mA output, an i/o pin is only guaranteed to give you 4.1V with a 5 V supply.....People that read datasheets already know this though.
Figure 35-24.ATmega328P: I/O Pin Output Voltage vs. Source Current (VCC = 5V)
And 20 mA with 5Vcc in worst case at *105 C* is just below 4.3V according to ATMEL. At 25 C which is warm it's just under 4.5V on the chart. I had the old datasheet more than a year ago and just got the updated one last week.
Unless those lines take a sharp turn between 20 mA and 40 mA, it stands to get a little below 4V. Will the DS18B20 run at such low voltages? Maxim says it can run on 3V.
Will it kill my 328P pin to push 40 mA for 100 milliseconds? I doubt it. But keep doing that and the lifetime of the MCU should shorten though I bet not drastically.No, it's not bright but, once again, it is possible.
Would I do it? It depends on what for. It's NOT a good idea, the charts only show to 20 mA for a reason but that is not because you will fall off the edge of the world if you do it. It's also not bright to overclock a CPU but that's done too and generally the CPU lasts until it's obsolete and so cheap to replace most people don't care.
I know it's not a great idea and far, far worse, I mentioned it to you.
*NOTICE: Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent damage
to the device. This is a stress rating only and
functional operation of the device at these or
other conditions beyond those indicated in the
operational sections of this specification is not
implied. Exposure to absolute maximum rating
conditions for extended periods may affect
Here's some bits from Maxim that haven't been brought up, possibly because they don't indicate parasite power as the end-all be-all mode for DS18B20 and offer just a little hope that discussion on powered mode won't result in death by boredom through repeated explanations of how the wonderful parasite mode can be the only way to use these chips.
If the DS18B20 is powered by an external supply, the master can issue “read time slots” (see the 1-Wire Bus System section) after the Convert T command and the DS18B20 will respond by transmitting 0 while the temperature conversion is in progress and 1 when the conversion is done. If the DS18B20 is powered with parasite power, this notification technique cannot be used since the bus must be pulled high by a strong pullup during the entire temperature conversion. The bus requirements for parasite power are explained in detail in the Powering the DS18B20 section.
And there's a whole section on TIME SLOTS. Just guessing but it looks like the things run faster when they're coordinated. But really, who wants THAT? It, gasp, uses an extra wire!
Parasite power is very useful for applications that require remote temperature sensing or that are very space constrained. Figure 1 shows the DS18B20’s parasite-power control circuitry, which “steals” power from the 1-Wire
How can this be when parasite power is the only mode these chips *should* be run? How dare they?
How dare -anyone- question using parasite power? If not in the Maxim doc then at this forum! It should be banned!
The DS18B20 can also be powered by the conventional method of connecting an external power supply to the VDD pin, as shown in Figure 5. The advantage of this method is that the MOSFET pullup is not required, and the 1-Wire bus is free to carry other traffic during the temperature conversion time.
You give me too little credit and you jump to conclusions too easily. You can't tell tell when someone makes anything like a less than a totally serious remark.
It's not like I asked or told about something that would cause bodily harm or legal proceedings.
Hey OP! I'd go with the power wire if I was you! It should be easier, cheaper and maybe faster not just running but getting debugged.