Zigbee tests

How’m I gonna put this into a cohesive post…

So I found out a few days ago that I couldn’t use the slip rings for transmission of data. Just not reliable enough. So I turn to wireless. I’ve used Zigbees in basic ways before with just one pair. For ADB, there’s several things I need to figure out. Networking of several nodes. Also, if I’m going to have Zigbees why not program my micros with them. Finally, Stability is important. Starting with the second task, if you watched the video in the last post you saw that it took two tries to upload new firmware to the device. I came to realize that it’s a difficult thing. Check out the Sparkfun Tutorial. As it explains bootloaders are generally intended for stable, wired connections, which wireless just ain’t. So they went ahead and made their own bootloader and uploading software, the latter of which is called Screamer. I tried it and it works great. It won’t bootload to several chips at once which I was hoping. It also only seems to work with Atmega168’s and I’m intending to work with the 644’s. Apparently it should not be too difficult to adapt the code but that’s perhaps above my abilities to timeline ratio. Taiya will likely be able to do this more readily than I.

I tested out the basic networking with Series 1 Xbees. It worked well. Fairly straight forward. Just power up several and they will talk to each other. Technically they default to a Point to Point network which had me a bit worried at first. But thanks to this explanation it seems appropriate.

As for stability, I found that 57.6k baud was about the fastest that I could transmit reliably. Also I found that an entire string will likely be transmitted without interference from a second device that’s talking at the same time.

two devices talking without delay

But a receiver will likely pay attention to the device with the strongest signal when two talk at the same time. I figured that out by simply covering up one device with my hand causing the receiver to switch between the two speakers. A good protocol with master slave setup should solve this I hope. Then only one should speak at a time. I tested such a protocol today and seemed to work alright. Although, one looming challenge is that it didn’t stand up to high speed situations…even moderate speeds…will look into more.

Dinner time.

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