Learning Objectives

We're going to undertake three activities in today's lab. It's gonna by fun and busy!

• Sensor board PCB layout design review
• MCU and power-board schematic design review
• Team work

Sensor board PCB layout design review

With your sensor board schematic finished and now laid out, it's time to undertake a review of your layout. Everyone should have their PCB layout finished and submitted as part of EX02.

We've gone ahead and done the review by putting comments on your layout in Altium365. If there are only small issues, you should be all set. If there are issues that are difficult to sort out via comments, then we'll grab you and talk them through.

What are we looking for? Primarily errors, but reviews are also a chance to give out tips.

Here are some things to look out for:

• Are all components wired up according to the schematic?
• Are the sensor ICs arrange at one end of the board, with the connectors on the other end? This makes for a tidy layout, and will make it easier to expose the sensors to the outside world
• Are all the component footprints the right ones?
• Is there is mostly solid ground pour on the back?
• Are the bypass capacitors close to the power pins?
• Are there holes for mounting the board to the enclosure?
• Will connectors get in the way of the attachment?
• Are there informative labels on the silkscreen, and are they oriented so that they are easy to read?
• Is there a board version marking?

MCU & powerboard schematic design review

Next, we'll repeat the schematic review that we did for the sensor board, but now for the other two boards. Same procedure as last week!

Here are some things to look out for.

For the MCU board:

• Correct ESP32-C3 package (aka -WROOM-02-N4)?
• Pins wired up correctly
  • 3V3: 10u, 100n caps to GND
  • EN: connected to switch (to GND), and to 10k/100nF R/C pair
  • SDA, SCL to 2-pin JST connector
  • LBO to 2-pin JST connector
  • GPIO8 to 10k to 3V3
  • GPIO9 to switch to GND
  • GPIO18/19 to D_N/D_P pins on USB connector
  • GPIO2 to 10k to 3V3
  • GND pins to GND
  • All other pins brought out to 8-pin headers
• USB connector
  • 22pF caps to GND on D_N/D_P lines
  • All shield pins to GND, plus pin 5
• Other connectors
  • 2-pin JST for power, ground
  • 2-pin JST for I2C
  • 2-pin JST for LBO
• Status LED on power rail, with current-limiting resistor?
• Test pads or vias accessible and labeled?

For the power board:

• Correct MCP73871-2AAIML and AP7361C-33Y5-13 packages?
• AP7361C
  • 4.7u on pin 5
  • status LED on pin 5
  • pin 3 to GND
  • pin 1 (EN) connected to pin 4 (IN)
• MCP73871
  • OUT (1, 20) connected together,
  • bypass: 4.7u cap to gnd on pin 20; 10u cap to gnd on VBAT
  • VBAT (14,15,16) connected together
  • PROG1: 1k to GND
  • PROG3: 10k to GND
  • THERM: 10k to GND
  • VSS,EP: to GND
  • CE, PROG2, VPCC: to 5V
  • SEL, TE: to GND
  • IN: to 5V
• USB connector
  • pin 1 to 5V, 10u to GND
  • pins 2-4: N/C
  • pins 5+Shield: to GND
• At least two JST 2-pin connectors
• Battery connector should be 2.0mm JST (B2B-PH-K-S(LF)(SN))
• test points on major lines

Team meeting

Now, on to the project. Use this lab time to work on your concepts in preparation of the first set of presentations next Thu March 2.

Details on the presentation are in Concept presentation page.

In particular, for each concept, work on:

• Industrial design for the HW node -- what does it look?
• A wireframe of the web front-end
• The current functional block diagram of the HW, FW, and SW
• Your current specifications, including ones not yet set
• Results of research, modeling, and prototyping that support your specifications
• A set of questions that need answering, either from the team, the staff, or the partner. These are the known unknowns.

And identify your team roles.