So… been playing around with a pair of CYD’s, which I intend to turn into sorta… weather clocks. To that effect, I also got some DHT22 sensors for temperature and humidity. The Particular CYD’s I got have a GPIO pin right next to the 3.3V out and a ground port, which is ideal since I could use a single cable bundle to hook everything up, but there’s one problem: The pin in question is GPIO35, is input only, and does not feature a pullup resistor.
So when testing, I hooked up a second cable bundle to connect it to a different GPIO pin. This worked as intended, with the sensor doing everything it was supposed to, at least as accurately as my existing temp and humidity sensors. That’s great, but I’d rather not have to go get additional cables.
So… I looked it up, found out it was supposed to have a 4.7kohm pullup between data and 3.3v, I hooked it back up to pin 35, overrode the config block, and tested it. I was hoping it would just work, since the board for the sensors does look like it has some resistors on it, but it did not. Well, no matter, I have a bunch of old resistors, so I pulled out a 4.7kohm resistor, tested it at 5.0kohm on my multimeter which… should be fine, and then hooked it all up. No dice. Still giving the exact same readings as no resistor.
So I made sure everything was connected, took measurements. The raw sensor module, between 3.3V in and the data pin, measured ~3.3kohms, and with the resistor in place, it measured ~2.0kohms, which… should be accurate for a 5.0kohm resistor running parallel, so it’s not that it’s not connected. Also made absolutely sure the pins were connected to the where they were labeled and everything. So… I should have the correct pull-up resistor there, more or less, right? But still no readings, unless I use the internal pull-ups.
Anyone have any clue what I might be doing wrong? Anything obvious I might be doing wrong with the resistor? Or am I just shit outta luck for using that particular pin, and need to go buy a few extra specialty connectors?