Buck board schematic peer review

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A Python Error Occurred:

Error on line 2 of Python tag (line 3 of source):
    board_kerbs = str(BUCKBOARD_REVIEWS[cs_username])[1:-1]

KeyError: 'None'

Learning objectives

In ex02 we captured the schematic of a buck converter circuit to turn a variable input voltage into a 3.3V output.

Just like for the sensor board, we'll undertake peer review before proceeding to layout.

Timelines

We have limited time for design reviews because we need to get on to layout.

You'll be assigned the three student designs Tuesday evening. Your reviews are due Friday 5pm.

Getting your peer designs

We've randomly assigned you to review 3 other designs. You've been assigned the schematics of: <div><font color='red'><b>A Python Error Occurred:</b><p>

Error on line 1 of Python tag (line 20 of source):
    print('%s' % (board_kerbs,))

NameError: name 'board_kerbs' is not defined
<p></font></div>

  1. Clone the repos. They will have very similar format to your repo. Open a terminal window. Navigate to the directory where you'd like to store these repos. Then clone:

git clone git@github.mit.edu:6-900-S25/buckboard-[kerberos].git

where [kerberos] should be replaced by the name of each student's project that you are assigned to. You'll clone 3 different repos.

  1. Open the project. From the KiCad main window, hit File->Open Project, navigate to the repo and select the *.kicad_pro file.

It's possible we've assigned you to review a schematic from someone who has dropped the class. If the repo you clone is empty, please send us an email.

  1. Open the schematic. From the KiCad main window, you should now see the *.kicad_pcb and *.kicad_sch files. Double-click the schematic file to open it.

If that all works you should now see your peer's design.

Doing your review

We're using the same process as for the prior two peer reviews, aka a markdown file.

  1. Open up your favorite text editor.

  2. Create a blank markdown file in the main folder of the design you are reviewing. Name it None-schematic-review.md. Save it.

  3. In your text editor, add two lines:

## Function

## Style

You're going to give feedback about the function of the design, aka does it work, and feedback about the style of the design, aka is it easy to read and understand.

Function

Here you're trying to figure out if there are any errors in the design that will prevent it from working.

Some checks to make (not an exhaustive list!):

  • IC is LM3671 with SOT23-5/SOT753 footprint
  • There should be two Cs and one L
  • One cap connected to VIN pin, 4.7 uF
  • One cap connected to output side of chip, 10 uF
  • One inductor of 2.2 uH
  • Cs, R, LED are 0805 footprint
  • Inductor footprint is weird, but not 0805
  • 3 or 4 2x2 connectors
    • Connector_PinHeader_2.54mm:PinHeader_2x02_P2.54mm_Vertical footprint
    • 1 connector has GND and power, labeled as VPP, VCC, VBUS, or something similar
    • the other connectors are 3V3 and GND
  • The EN pin is tied to the same node as VIN pin
  • The 3V3 node is on the far side of the inductor
  • One LED with series resistor, powered by 3V3 node (a 2nd LED/resistor on the VIN side is also fine)
  • Running ERC returns no errors beyond "Input power pin not driven by any Output Power pins"
  • Testpoints on VIN, 3V3, GND

Note that this isn't a complete list. Use your judgement if you see any other issues!

If you find an error, add a line to the Function section, explaining the issue and being as specific as possible. For example:

## Function

* C1 and C2 are not connected to ground
* Missing testpoint on EN pin

## Style

If the design has no functional issues, write that:

## Function

* No issues

## Style

Style

Here you're trying to give feedback to make the design easier to understand for others, since one role of a schematic is to communicate with humans.

Some checks to make (not an exhaustive list!):

  • Parts and their text are not overlapping
  • Use of net labels
  • Label connectors with a name that makes sense, like power in, or out

If you find a style issue, add a line to the Style section, explaining the issue and being as specific as possible. For example:

## Function


## Style

* R1 and R2 are overlapping

If the design has no style issues, write that:

## Function


## Style

* No issues

Feedback doesn't necessarily need to be constructive. If the schematic you are reviewing has no issues in a section, leave two points about aspects that are well done in their design pertaining to that section. Positive feedback is also valuable feedback!

Finish and submit your review

  1. When you're finished with your review, save your markdown file.

  2. Then stage, commit, and push the review.

Here we only want to stage your markdown file. Don't stage everything as you don't want to mess with your peer's design in case you made any inadvertent changes in KiCad.

git add None-schematic-review.md

git commit -m 'peer review by [your kerberos]'

git push origin main

Close out of the schematic file. If prompted do not save any changes to the schematic file.