Eric Maynard’s Status Update for 2/22/2020
What did you personally accomplish this week on the project? Give files or photos
that demonstrate your progress. Prove to the reader that you put sufficient effort into
the project over the course of the week (12+ hours).
I set up the microcontroller on a breadboard to measure power requirements, clock skew, and boot time.
The result of the boot time test was that it is not perceptible. As a result, we have removed the boot time from our model of codeblox. This link is to a video of our boot demo.
https://photos.app.goo.gl/r5nq3Lmh7qaws2mAA
The results for power requirements were 10mA at 5v and 3mA at 2.83. 2.8 volts was the lowest voltage we could drive the micro-controller.
The result of the clock skew measurement is that we can reliably transmit in words of 10 bits.
I ran a script to switch digital output every 500 micro seconds and measured the variation of clock periods. I wanted to confirm that the micro-controller’s internal oscillator is reliable enough to measure data sent at 1kHz rate without a reference clock. The measured period varied by 20 micro seconds. Compounded over a 10 bit word of data, the greatest drift that could occur is 200 micro seconds, which is within our 500 micro second window. Because of this, we can reduce our circuit to just one data out and one data in circuit per side of the tile.
The largest consequence of these three tests is that we no longer believe we need a backup battery. We originally wanted a backup battery in case of temporary tile disconnections, to avoid having to reboot the tiles. During an interrupt in power, we would reset the state of each tile and go into a low energy sleep mode. Then upon re-connection, the tile would not have to reboot, but would have to restart any compilation task that had been initiated. Because the boot time is negligible, there is no advantage in our current design for keeping batteries in the model.
I also got comfortable with Eagle CAD to design the PCB’s and created eagle components for the parts I wanted in our schematic that did not have cad models on digikey.
Is your progress on schedule or behind? If you are behind, what actions will be
taken to catch up to the project schedule?
I am still behind. I want to finish the eagle schematic and pcb layout for the design presentation so that I can order all the components and build a initial prototype next week.
What deliverables do you hope to complete in the next week?
Finished schematic and pcb layout.