I am using a ds18b20 Dallas thermometer that communicates with Maxim's one wire protocol. I'm having issues at the initialization sequence. I have pulled the line high for 500 uSeconds, pulled the line low for 510 uSeconds (the reset), pulled high for 45 uSeconds, waited for 120 uSeconds for the thermometer to pull the line low as a response (the presence pulse), and then sampled the signal to make sure it was low. If it is not low, something went wrong. When I look at the signal in my 'scope, I see it get pulled down for 510 uSeconds and the pulled up for 680 uSeconds. This means the thermometer did not respond at all (45 + 120 + 500 = 675 uSeconds). What am I doing wrong?
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