RFID Children's Game



RFID Children's Game

Jared Wilkin and Chris Good

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Issues Resolved and Pending

The main issue that was raised in the previous update which was our biggest unknown has been solved. Our biggest hurdle was to correctly send and receive packets from the ipaq out over the wireless camby. We know this has been solved because our experiments have yielded enough positive data for us to be sure it is working correctly. Our chief experiment for this unknown was to have a mote attached to the serial port of our PC, on which we had a listener running. This listener just printed to the screen any packet that the mote received. We then had another mote sending out a steady stream of packets that we hoped would be picked up and read by the ipaq. The first success came when we were able to print out the packet contents to the screen of the ipaq. The next success came when we were able to call the blocking select function and successfully return from it when a packet arrived. This was huge as our game engine relies heavly on listening for packets while interrupts move the game along. The final success for this experiment came when we sent packets out from the ipaq which caused correct behavior in a mote which meant that the mote received them correctly.

Another unknown that we solved is which language to use on the ipaq. We decided on C since the game relies heavily on speedy wireless communication and we didn’t want to take the chance that a java program would be too slow. We had to sacrifice having a pretty gui to do this, but we believe it was the right choice.

One final unknown that we solved was what type of switching mechanism we are going to use for the lights. Initially we planned on having high voltage halogen lights which would require some sort of transistor circuit as the mote is only 3 Volts. After thinking about it and doing some testing we decided that it would cause much to much drain on the battery. So we opted to just use LEDs instead. This meant that we could run them directly off the mote pins and didn’t need any sort of transistor.

After solving all of our previous unknowns we ran into a very minor unknown that is at the moment still pending. After we got the motes communicating with the Ipaq, we sent a command telling the mote to turn on all of its lights. After testing the pins on the mote with a multimeter, we discovered that only 2 of the 3 were high. We then sent a packet telling the mote to turn all of its lights off and the same 2 were high. This could mean one of two things. Either we aer not controlling those pins correctly, or they are being used for something else. At present we don’t know which it is so we are in the process of running tests to solve the problem.

Components and their Use

As stated in our previous update our design is relatively simple. It consists of a few software modules and a couple hardware components. As of this point we have received at least one of every hardware component we need. We have also been able to test each hardware component and we are confident that each one will operate as we need them to. This includes making sure the RFID readers correctly send the ID tag via serial to the mote, making sure each mote can correctly handle the tags as well as respond to commands to light LEDs, and checking the data communication between the camby and the Ipaq. Since all of these components have been tested and seem work like we expect them to it leaves the software components to check.

As of right now we have begun work on each needed software component, but until now we have mainly concentrated on the hardware side. Since we are now sure that the hardware is working correctly we are confident the software side will come quickly and work how we need them to.

Construction and Debugging Plan

Currently at least one instance of all the hardware pieces have been built and tested. This includes the RFID reader/Mote set up that is the majority piece of the game stations and the team reader station. The only part of those stations that hasn’t been completed yet is the housing they will go in. We have built the communication software layer between the camby and the C program running on the Ipaq. This layer has been extensively tested so we are completely confident that packets being sent from the C program are making it correctly out on the radio. The only major piece left to be completed is the Base Station code running on the Ipaq. This will just consist of data structures and timings that will cause the game to work.

We have the basic pieces in place that will be there for the demo, but the actual game isn’t working yet. We can send commands to the Game Station and have it light a given light. We can also read a tag and print the tag on the screen of the Ipaq. What we need to do now in order to get the to a point where we can demo the game, is to put all the pieces together and polish the UI. page.

Appendices

Software architecture drawing showing all major components and the communication between them:

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