Month: October 2022

This week all of our parts that we ordered came in and I was able to connect all of them to the RPI. I mainly worked on interfacing with the GPS/IMU. Zach and I think it would be a good idea if we could have something running by the end of this week that would allow us to gather location data while walking around. This way we can walk some routes and save the data so we can simulate walking the route at a later time for development purposes without having to physically be walking the route whenever we want to test.

This brings up the need for some mobile system that includes a power supply and a case to protect all of the components. I should be able to throw together some sort of case quickly, however I need to get the battery ordered. I did some research about batteries for the design report and found this 26800 mAh battery: https://www.amazon.com/Charmast-26800mAh-Portable-Li-Polymer-Compatible/dp/B07P5ZP943. The battery outputs 5v which is how much voltage the RPi runs at, and since our design constraint of battery life is 16 hours, this gives us 8.375 Watts maximum. The RPi uses about 5 Watts at 100% CPU load, and the peripherals will use less than 2 Watts combined, giving us about 7 Watts of power being used. This estimate is on the high end and we may be able to go much lower with careful attention to minimizing power consumption. This battery will give us an estimated 1.375 Watts of slack which is a comfortable amount, especially because I do not want to rely on the battery performing properly at less than 5% charge.

My goals and schedule have somewhat changed from our initial thoughts, with the need to get some real data quickly, I am now focusing more on the construction of the device and the battery. I aim to receive a battery next week and perform some route walks while gathering the location data along the way so that we can do testing/development. I will be somewhat ahead of schedule regarding the battery and device development, however I will be going slightly behind on schedule regarding the wireless communication aspect of the device in order to focus on the location data collection.

This week I accomplished everything that I wanted to based off of my prior status report. I wanted to get all of our hardware ordered (except for the battery) so we could begin to experiment with the equipment as well as working out a framework for the software to run on the Raspberry Pi. Zach and I also spent a lot of time on the design review report.

Most of my time this week was spent on developing the software to run on the RPi. My main goal was to come up with a system where all three of our main threads could run while communicating with each other. I decided to add a fourth overall thread to the system which would be the controlling thread. This thread tells the other three threads when to run and handles the data communication. Since we will be using a single process and asyncio in python to be able to run threads, we do not have to worry about concurrency issues when communicating data since only one thread will be running at once. The controlling thread will initially tell the location thread to gather location data, and then put that data into a buffer. Then the second thread that will be interpreting the location data and communicating with the API’s will be called. That thread will be given the buffer to take the location data and then use it to determine what sort of feedback to give to the user. The feedback will then be put into a separate buffer and given to the third thread by the controlling thread. The third thread will then run the text-to-speech engine and output to the 3.5mm audio jack for the user to listen to. This process will continue until the user has reached their destination.

Next week I would like to hook up our components that have been ordered into the physical system. I would like to communicate to the components through the software and be able to gather the necessary location data to be able to know where the user is. I would also like to hook up the software to the blues wireless notecard API to be able to communicate to our external directions API. If I could get all of this done next week I would be on schedule and I would be able to begin to collaborate with Zach in order to start getting the skeleton of our entire system working. We would hopefully be able to have the hardware supplying data to the directions thread which would allow us to work out the next steps to a fully functional system.

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.

This week our team altered our project to now provide directions along blind-friendly routes to aid the visually impaired. Due to Eshita dropping the class, Zach and I lack the machine learning knowledge to be able to proceed with the prior design.

I will now be focusing on the front-end of our system. I will be using a Raspberry Pi to gather data from a GPS unit to be able to determine the user’s location. The SparkFun GPS-RTK Dead Reckoning pHAT board appears to be a good unit for the project. The unit attaches to an RPi4 through the 40 pin header, and is easily interfaced with I2C. The unit contains a GPS locator, and an IMU to provide more accurate position readings when a loss of GPS signal is encountered. The unit has heading accuracy of within 0.2 degrees, however the unit does not contain a magnetometer. It achieves this by relying on the GPS moving, combined with accelerometer readings. This may be a potential problem for us given that our user may be standing still for a long period of time, and the heading reading will be prone to drift without the user moving in a direction. A solution to this would be to add a secondary board with a magnometer to tell direction, however this may not be necessary will significantly increase complexity of the unit because we would no longer be able to use the PiHAT 40 pin connector for the GPS and we would have connect both boards to the RPi, sharing the header.

I will also be taking commands from the back-end Pi to give directions to the user via audio. I will be using a Text-To-Speech engine to tell the user where to go and give various status updates given from the back-end Pi. The RPi4 comes with a 3.5mm audio jack capable of outputting audio to a wired ear bud which the user will be able to hear the directions from.

I am currently behind schedule given that our team is re-designing the project, however I am very happy about the new direction of the project. In the past day we have been focusing heavily on the project and will continue to do so in order to have a good design done by Sunday for the design review.