Computing stuff tied to the physical world

Demo remote LCD

In Hardware, Software on Apr 6, 2010 at 00:01

It’s hard for me to realize just how confusing all this Jee stuff can be, and it’s certainly good to be reminded of that once in a while. Not everything makes sense for people who aren’t immersed into all this every day.

I want to improve that. In fact, it’s the main reason I’ve been chasing around in search of a good forum + wiki setup. As it stands, I’m hesitant to start writing down lots of things and, eh… yes, documenting all this Jee stuff. But this will change. Promise.

For starters, some good news on the forum + wiki front: I’ve decided to standardize on Markdown as formatting language. It’s ancient (i.e. proven), it’s clean, and with just one or two extras it will be good enough for most of the things I need. The reason I’m bringing it up here, is that I’ve just finished converting all the wiki pages to Markdown, as well as 90% of the current Jee Labs documentation pages. The forum remains bbForum, but it has now been adjusted to use Markdown formatting as well. So has WordPress. In fact, this is the first weblog post written in Markdown (in Textmate, my favorite text editor).

Yeay for one set of conventions, and yeay again for simplicity!

Ok, back to the main topic of this post.

Here’s a demonstration on how to send a text string to a remote LCD via wireless JeeNodes. This is the hardware I’m going to use for that remote LCD node:

  • a JeeNode USB
  • an LCD Plug with 2×16 LCD display
  • one extension cable
  • plus a hookup to USB to power this whole thing

Dsc 1300

Ok let’s set up a simple demo sketch for the remote receiver end (code here):

Screen Shot 2010 04 05 at 20.09.58

Very simple, really: wait for an incoming packet and display the bytes as characters on the LCD. Plus some initialization code.

On the sender end, I’m using a JeeLink running the pre-loaded “RF12demo” sketch:

Dsc 1302

First step is to put the JeeLink in the right mode:

8b 4g 1i

That’s the 868 MHz band, group 4, node ID 1.

Now we can send a message to node 9, which is running the remoteLCD sketch, by sending a packet with the individual character codes to the JeeLink (the “9″ at the end is the destination node ID):

84,101,115,116,32,49,50,51,9s

The result:

Dsc 1305

Yippie. No wires. Magic! :)

  1. This is awesome! I was fooling with this and it works great. so quick question, if you receive data. Say 35 121 29 ack

    How do we translate incomming data back into the display output?

    Because I believe I will have to do something like temp= 121 + 256*29 I bet I am going to have to do something like temp = a[1] + 256 * a[2] Or something like this. To then take and print out the temp item in something that is going to be human readable in the display. Got some hints?

    • Does this help? http://talk.jeelabs.net/topic/218/page/2

      BTW, your question could make a great demo. I’ll see if I can set up a network with three nodes, sending the room board data to the central JeeLink, then to JeeMon, then out to another node with LCD. But it will take a few days, got some other posts planned first. Thanks for the idea!

      (P.S. It’s probably better to continue this discussion on the forum)

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