Status Reports

REV 1 SCHEMATICS: I completed the schematics for Rev 1 and sent them out for review on Monday (3/1/2021). The response from our reviewers (our TA and advisor) was mostly positive, but our TA identified a new ADC component which could offer superior performance over our existing solution, which led me to redesign the input stage with input from my teammates and our advisor on Thursday/Friday. The new input stage features a 4-channel audio ADC which communicates with the microprocessor on SPI and a new audio-class amplifier for the preamp block.

REV 1 LAYOUT: In parallel with the above, I began laying out the Rev 1 PCB board. Rev 1 is a mixed signal board including both audio and RF signal paths, as well as moderate-frequency digital signals, necessitating care in layout.

As can be seen in the image above, I’ve finished internal layout for most of the main blocks, including the Analog Effect, LCD bus, and BM83. Most of the Power Module and part of the UI module remains to be routed, but I expect that I am close to completion because the routing for these remaining components is less complex than what I have done so far.

DESIGN REVIEW PRESENTATION: I will be delivering the design presentation next week, so I have been working together with my teammates to create the slides and understand the content I need to present, which includes substantial work that was not done by me. We plan to hold a dry run presentation on Sunday before the slides are due.

I had previously hoped to finish the layout and order the board by the end of this weekend. However, due to the late redesign with the ADC, it seems more realistic to let this deadline slip by a few days and order the PCB before Wednesday. Finishing the layout and all of the associated tasks necessary to order this PCB will be the main focus of my effort in this coming week, along with participating in the design review process. Overall impact of this change on our project schedule should be minimal.

ANALOG EFFECT: This week, I completed the Analog Effect circuit (a 3V3 clone of the Colorsound Overdriver). By importing WAV files into SPICE, I was able to verify that the circuit produced the intended modulation effects, and was not functionally affected by my revisions to make it 3V3 compatible. This gave me the confidence I needed to implement the circuit using real hardware in the Rev 1 Schematics.

REV 1 SCHEMATICS: As planned, I spent the majority of my time this week on the schematics for our Rev 1 board, a near-complete prototype of our project hardware which has fewer audio channels but contains all of the necessary peripherals. I have sourced essentially every component in the design, and I am filling out a BoM for delivery to PCBWAY in conjunction with the schematics.

Currently, the schematics are approximately 90% complete, pending feedback from my teammates and a few small changes. The plan is to complete the schematics in the next few days, followed by a design review with our TA / advisor. At that point, I can begin laying out the PCB with a goal of sending it out for manufacturing by around the end of the coming week. This will enable us to verify our software on actual hardware.

In the coming week, I will also be preparing to give the Design Review presentation, which is my designated presentation to give.

90%-completed schematics are attached to this update.

Rev 1 Schematics V0.9 WIP

The portions of the project for which I am responsible remain on track or ahead of schedule. The objectives I focused on this week include:

PROJECT TEST PLAN: I wrote the BARI Test Procedure document, outlining a set of ten quantitative tests that we will perform at various points throughout our project to verify System Requirements. In my section of the proposal slides (metrics and testability), I linked these tests to the System Requirements they verify. Most tests remain as outlines, but several are fully written out with instructions for recording results.

PRE-AMPLIFIER: I have selected an overall topology as well as specific components for the BARI pre-amplifier functional block. Through the use of a switched gain block and attenuator, the pre-amplifier will achieve tunable gain to within +/- 1 dB across a 70 dB range. See Slide 8 of the Proposal Slides.

ANALOG EFFECT: Sam helped me downselect to the “Colorsound Overdrive” pedal, an analog effect that is only available in expensive pedals and will be an excellent selling point for our product. We have reference schematics from several sources for the Colorsound, but it’s my responsibility to (1) Verify the correctness of these schematics and create a Reference Overdrive Pedal model in SPICE, and (2) redesign the circuit to function at 3V3. (The original circuit runs from 9V.) As of right now, I’ve subdivided the Colorsound Overdrive into three stage (fuzz face, tone stack, and output amplifier), and I’ve created both 9V and 3V3 versions of the fuzz face stage.

REV 1 SCHEMATICS: This weekend I am beginning to work on schematics for our Rev 1 circuit board, which should be a fully functional prototype of the system. I have an aggressive deadline to complete these schematics in time for a schematic review on 3/1.

In the coming week, I plan to focus entirely on finishing my redesign for the Analog Effect and finishing the Rev 1 Schematics. This will also enable me to help the team create power and fiscal budgets, since the Rev 1 (and Rev 2, if necessary) boards will be a large part of those budgets.