This week I worked on figuring out the compatibility of the parts that we want to use on the project. Initially, we thought about using two RPIs, and dedicating one to the front end and one to the back end. The only reason for this would be to make the GPS and cellular data card easier to hook up to the system. However, the increased development time and complexity of two RPIs communicating data to each other is not worth it. I did some research on the data card and the GPS and have determined that we can hook both of them up to one RPi. Since we aren’t going to be anywhere near the computational limits of the RPi, it seems as if the most logical route to take. The GPS unit has the ability to change it’s I2C address, so we can run both the GPS unit and the cellular data card on the same I2C lines. An alternative would be to communicate to the cellular data card via I2C, and the GPS via UART if problems arise.
I also did research on the environment we will be running our tasks in. I originally contemplated scheduling 3 separate python processes on the RPi kernel, one for GPS data gathering and filtering, another for the backend, and another for the audio output, however the communication of the data to and from each process is not simple. An easier way to do this would be through the use of one single python process utilizing asyncio to perform cooperative multitasking with each of the 3 threads. Since we are not bound by computation power, we do not need to utilize all of the cores on the RPi, and this would allow for data communication between the threads to be much simpler. We also do not have very hard RTOS requirements, so we do not need preemption if we work out a simple cooperative scheduling scheme. Any extra development time that can be taken away from the environment that can be put towards the main direction algorithm of the project will be very useful for us.
I am doing okay in terms of the schedule. I accomplished a lot of what I wanted to in terms of figuring out exactly what parts to use and how they will communicate with each other. I have ordered the RPi from the ECE inventory, and have figured out what we will be running on the RPi in terms of software. Something that I would have liked to get done was to actually receive the RPi last week, however I was not able to and I will be doing so Monday morning.
Next week I need to get a few things done. The first would be to set up python on the RPi and start on the frameworks for all of our threads to communicate with eachother. The most important goal for next week is to order all of the extra parts that we will need for the project. Those parts would be the GPS/IMU, cellular data card, antennas for both of those parts, and some wires to hook up the devices to the RPi.