This whole week was spent inside of eagle. I started by making a breakout board for the new lower power gyro. This took a long time, since this gyro is not offered by one of the big hobbyist sights I had to create the eagle part from scratch and design the circuit myself. Luckily the the data sheet has a suggested circuit in it that I was able to use with a few small tweaks. The data sheet schematic does have a few weird things in it though. For one it has one pin connected to a 01.uF capacitor, and another pin in the same design connected to a 100nF capacitor. These two values are of course the same, and it’s weird to write the same number two different ways in the same document like that.
In addition to creating the gyro board I also began work on an evaluation board for the microSD card slots we’re considering. We have gotten down to 3 slots and I am going to build a board with all 3 on it and then chose the one I like the best.
I will probably order these boards later this week and I’ll make sure to give updates when they come in.
Home coming week was pretty crazy so I did not get a ton of time to work in the lab. Most of the week was spend doing research. I researched BLE chips and am getting closer to finding a chip and a way to integrate blue tooth into sharkduino. I also spend a lot of time reading the data sheet for the new gyro, making sure I know how it works and will do what I want. I will start design a break out board for it soon. Finally I did a poster presentation at the W&M Physics fest. This was a lot of fun and it is always great to see what everyone in the department is working on.
Next week things will have settled down and I’ll have so more substantive and exciting stuff to talk about.
Fall break was this week, but that doesn’t mean I did not get some good work in.
I started the week by looking more closely at layer 3. What I wanted to figure out was if the the temperature sensor is necessary or if the one integrated into the pressure sensor is good enough. To do this I just had the two sensors output the temperature and compared them to each other at a range of temperatures. I found that temperature sensor can give more significant figures and responds more quickly to changes in temperature. The data sheet says that the temperature sensor has about ±0.5°C while the pressure sensor only claims ±2°C. This seems realistic from my tests. To decided if I will keep the real temperature sensor I still need to meet with the rest of the team and flesh out how much precision and response is needed by the temperature sensor. Getting rid of if would reduce both the power draw and complexity of the system, which is a definite up side.
Also this week the boards for the new RTC came in. I worked on assembling them and determining an optimal order of operations for assembly. The first one I fully assembled worked, which is always very exciting. I was able to confirm that it is programmable over I2C with a 3.3v Arduino Pro Mini, and that the alarm interrupts seem to be functioning as expected. Now I’m going to assembled two more of them, and go forward with the sharkduino design overhaul with confirmation the new clock circuit is good. A picture of working breakout board is below.
DS1339 breakout board
Sorry that this week’s post is a little late, I was busy.
I began the week by setting up and testing the adafruit Bluetooth Low Energy (BLE) breakout board. It was fairly easy to get up and running. I was able to get it to work and stream sensor data in real time from my phone to an arduino. I feel pretty good that I can get BLE working and use it to do what we need.
Next I tried to get the adafruit NFC board to work. This was not nearly as easy or straightforward as the BLE. I spent a few hours fighting with the board and the code to try to get it work. I ended up giving up on using SPI on it and was going to try again later with I2C. However I never did this because in the meantime we had a meeting and it was decided that we would use Bluetooth in the sharkduino because it is more commonly used and has more support. I may go back and play with the NFC more some other time just so it has not bested me, but it will not be used in the project.
I also did more work with the inductive charging. I connected one of the coils to a LiPo charger and battery and successfully charged a battery wirelessly. I now need to look into how I want to embed this technology into the project.
Finally I got in a big shipment of uSD readers. I got a bunch of different ones with different types of holders for the cards. The readers are cheap enough that it seemed easier to physically buy a bunch to look at then try to figure out which holder is the best just from the data sheets. I think that I’m going to go with a push pull reader for the Shakrduino, now I just need to decided which one I want and make a test board for it.