With the complete PCB design, we removed some of the planned backup plans since they were not feasible. The big one is that we were planning on leaving some extra DNP pads for more green photodiodes in case our photodiodes are not strong enough. However, there is slightly more risk now since we had to remove this to make layout work.
We noticed that the FPGA board lists some pins as clock pins. The Datasheet does not describe what this means. This is 2 pins from the FTDI chip and the 2 IR laser controlling pins. If this ends up being an issue, we can accommodate it by using an interface with the FTDI chip that does not use those pins (fast serial) and by testing that the IR laser pins operate at high enough speed.
Design Changes
Our PCB will be much smaller than the FPGA board rather than a copy of it. This is because the parts fit on a much smaller footprint, and making it smaller makes buttons and LEDs on the FPGA board accessible, and it will be easier to make sure the boards fit together.
Updated Schedule
In terms of schedule, software developments (Roger) were impacted by inability to develop software for hardware that had not been fully finalized. We have instead begun working on sender implementation as well as a preliminary UI interface to input text files for sending in order to be productive within the schedule constraints.
No changes have been made to the hardware schedule as the PCB and part orders went out on time
Progress
PCB design is complete! Our PCB and all components for it have been ordered and should arrive by the time we return from spring break.
Sender implementation for the bitwise hamming encoding of files has been implemented
We completed our design report paper
New Tools
We will need to learn to use FT_PROG to program the EEPROM to save settings for our FTDI chip
We will need to experimentally identify the best way to view the infrared laser for debugging and testing. We currently plan on using the front-facing camera from our phones, as they typically do not have IR-cut filters. However, this may not work. In that case, we will need to learn to use an IR camera to measure it.
This week, I completed our PCB design. I did our layout and it passed all DFM checks. It is currently in fabrication at JLCPCB and expected to arrive before class resumes after winter break.
I ordered all parts to make our PCB. Our only expected expense that has not been purchased yet is 3d printer filament. This has 1 day shipping so can be purchased later. Setting up our part orders was a bit complex because I wanted to order with bulk discounts where possible and buy extra components in case we need them, but we are running a little close to the $600 budget. I ultimately ordered enough active components for 3 boards and numbers of resistors and capacitors to get bulk discounts.
I wrote my parts of the design report. This was a lot of work to do in parallel with finishing and ordering the PCB, but we managed to finish it.
Schedule
My parts are on schedule. I planned on having the pcb ordered before spring break and set to arrive after spring break, and it should be here by then.
Deliverables
For next week, I plan to have 2 PCBs fully assembled and ready for use. This should be achievable, since all of our parts will have arrived before the beginning of the week.
