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Class 9

Last time we talked about general serial radios.Talked about transmitter-receiver vs. transreceiver. Sending ASCII is really useful, you can always send ASCII and then convert that to what you want in the receiver side. AS we remember, receiver always gets some data from the air, even if it is not paired with transmitter. So sending ASCII makes sense since we can differentiate between ASCII and garbage. Their baudrate is 2400 instead of typical 9600 we are used to. Typically they run about 3.3 to 6 volts.

We can use the AT commands to list the blueradios in our range. Maybe we can use this information to do something. Ethnernet Mac address plus bluradios addresses are being bought from Cambridge and assigned to companies. So we have similar numbers.

It is very good for onetoone peering. It is not so good to do general stuff. Writing below programi s hard to do for arduino. How do we do this with a program?

reset “AT” wait ok/ nothing ok > check stat > look > colllect…

Zigbees

ZIgbees are much more like UDP. They have an AT command set. It is another AT command set but structure of it is the same. Also like bluetooth we have command mode and data mode. (We have this changeable mode in lantronix too) Data mode vs. command mode is important. When you send +++ it will disconnect and go into command mode. In zigbees the nice thing about them are they go in data mode.

You can get the datasheet from maxlink site.

In order to connect our device to another device first we need to get the address. 64 bit address, two 16 bit words. IT drops into data mode pretty easily so you need to send +++ without a carrier return. ATSL is low mode. first part of the address ATSH is high mode. second part of the address

The address is reverse side of the zigbees. S is the serial number D is the destination.

Keeping lastSensorReading makes us send data over a threshold, when the data is changed.

WR means save this into non votalite memory! HandleSerial is something that we read the byte and change the string into number and and light the led. So we are sending strings of numbers to light up the leds. In the program we need to send our address first. It does a network stack. Collision could be a problem in order to avoid it we can listen too much and send too less.

Each zigbee has two unique address, hardware an software address. You can do a broadcast too, it will send to every zigbee on the floor with that message. But the listener says only listen messagges that start with certain headers. You can do personal area network to avoid collision too. There is a wikipage to get that.

Radios have high frequency signal strength. So doing a triangulation is not the best idea. In order to do that, you can get a audio streength sensor hooked up to the zigbee and gowith that. Ultrasonic sensors maybe . RSSI. Realtime location systems RLS are expensive. You are going to get indirect reflections of the signal which are multipass and it will interfere with the direct signal.

Projects

Dirty Nails

10 arduinos 10 plants 10 soil moisture sensor 10 light sensors. Basically they are going to log plants over time and plants will tell us whne they need water when they have too much water etc.

Logging a data from a plant could be interesting. Could this tell us something we don't see with bared eyes? David's project about touching and feeling remotely is interesting too. What if we just connect those people and get feedback and basically turn this into a conversation.

This page last modified on 2006/10/31 11:39.