Has anyone already done this? A cursory search of the codeshare brought up a DHT11, DHT22 on a FEZ with two pins In and Out tied together for some interrupt reason. It also brought up Gus’ SHT11 EMX version but that’s a serial port version and I’ve just got the plain vanilla RHT03 units from sparkfun or adafruit.
All I want to do is plug about 4 or these into an extender board off my spider. I’ve got the temp/humidity module which is great if you want to tie up one socket for one input, and I’ve already worked a DS18B20 interface and have 6 of those tied off of a single extender module (works great BTW).
Any tips/guidance would be appreciated. Although I could do this myself, I’m just not finding enough time to get it done…
This unit has VDD and GND plus one data pin. Unlike the DS18B20’s though, you can’t share data pins on this device, you must have a data pin per device.
I don’t know the full reasoning behind the use of two interrupt capable pins. You’ll need to check the datasheet and code, and prove that you do or don’t need that for your module, but from what I remember of the conversation at the time this was to avoid the use of RLP.
Your biggest issue will be interrupt pins, there really isn’t a concentration of them anywhere on a socket. So you may in fact be stuck with 4 extender modules on 4 sockets, one for each module. That is unless you can rewrite the code in RLP and remove that dependency. Then, you have many more options to achieve what you want on a single socket/extender.
Thanks for the tip. Ideally I’d like to get more than one on a port but if I have to go one per extender, I suppose that will have to do. As for using the extra pin, I didn’t read enough into why that poster did it. Instead I just figured I’d start from scratch. It’s not like it’s that hard. Getting a bunch of DS18B20’s running off one extender was pretty nice, but I’m nearly out on my Spider…
DS18B20’s are special in that they are designed to work in a bus scenario, these units aren’t. In fact, many times sensors like this must not share pins. Other bus types that can share pins (reducing your pin count) are I2C, that shares all pins as it uses a device’s address to communicate to it, and SPI that uses a dedicated Chip Select pin per device.
Thanks, I’ve got that bit. My post is for multiple DHT22s on a single extender, NOT sharing a single pin like the DS18B20. It’s pretty clear on the data sheet that while it refers to the connection as a one wire connection it’s NOT a multi point one wire connection like those found on the Dallas devices. Your first post on interrupts leads me back to the socket and pin out pages somewhere n the wiki… If I had only bookmarked them this would be easier!
So it looks like pin 3 is an interrupt pin on most sockets. I’m typically using and X or Y for these sorts of things so it looks like I may be stuck using the previous code. I suppose I could get all 4 working on a single Y based extender.