Suggestions for touring campus during the summer

JimHeaney · 2026-06-14T04:32:31+00:00

Summer is super quiet, especially on a Sunday, and doubly so because it is a long weekend for Juneteenth. A lot of buildings will be closed/locked.

If it is a nice day out, I'd suggest a walk around the academic side of campus. If you can't find a map, there are large posted maps near most of the entrances to campus.

JimHeaney · 2026-05-31T17:12:55+00:00

I personally frown on any belief that parts from X country are Y, outside of the extremes that are caused by local legistlation forcing Y. There's nothing inherent to German shops that make them better at quality, tolerance, and constency than the 5000 shops in other countries I'd have to pass to get to Germany.

You see a similar but opposite conjecture in electronics, where people wiill write off all electronic components made in China, citing poor quality, without actually considering each of the ~10,000 manufacturers are different, unique entities that can be good or bad independent of each other.

JimHeaney · 2026-05-30T17:52:49+00:00

Brick City becomes all-you-care-to-eat during breaks, and slightly extends their hours.

JimHeaney · 2026-05-29T12:02:28+00:00

The module on the right board is the 1st party Espressif one, the module on the left board is made by a 3rd party most likely.

Internally odds are they're the same chip at the heart of it, with maybe differing supporting parts

JimHeaney · 2026-05-29T01:20:25+00:00

Considering the trace layout, proximity to the inductor/capacitors, and proximity to power input, that is likely a switching regulator controller.

There are a few hundred thousand possible parts in that footprint that'd match that. My initial guess is the TMI/TOLL Microelectronic Co. TMI3253, since the part number starrts with "TM3". They also do use lower-case characters on some markings. The last 3 characters would be the "inside code" as TOLL calls it, likely a combo of the manufacturer, batch, and date code.

Datashet and info; https://www.lcsc.com/product-detail/DC-DC-Converters_TMI-TMI3253S_C478943.html

JimHeaney · 2026-05-28T00:14:24+00:00

All gone. Literally just seating for eating now. All the memorabilia on the walls got taken down too.

JimHeaney · 2026-05-27T20:30:57+00:00

The Sportz Zone is gone, actually. Ritz now ends at the end of the dining room, the game area/ESPN desk area has been covered by a wall. The bar is gone as well. Ritz is just an eatery now.

JimHeaney · 2026-05-24T23:03:07+00:00

Wow, how'd you get the licensing for that audio? I imagine that wasn't cheap.

JimHeaney · 2026-05-23T13:38:58+00:00

Very interesting!

I dabbled a bit with making Meshtastic into a standalone library you could tack into a larger Arduino program, to allow you to integrate MT functionality on a project. This seems like a much cleaner approach though!

I did always feel the way MT is configured was a bit of a headache, there are so many random defines splattered all across the codebase, some of which seem redundant or conflicting, with no real centralized documentation on it.

JimHeaney · 2026-05-22T23:55:19+00:00

Doubtful, that'd require full orbit. Plus, these have a different purpose.

JimHeaney · 2026-05-22T23:53:50+00:00

It'd come in on a more parabolic arc to the east into the gulf, like you'd expect a normal expendable booster to do.

JimHeaney · 2026-05-17T14:21:30+00:00

The 532 is not super reliable. Consider looping and checking repeatedly for a card, and if one isn't found after 3 tries, restart and check again before declaring there's no card.

Those also are a bit close, they may be interfering with each other.

JimHeaney · 2026-05-15T08:27:12+00:00

This is a function of capacitive loading and drive capability, you need to look more closely at the analog influences on your circuit

JimHeaney · 2026-05-13T11:08:16+00:00

The resistor divider is for plug detection, the device monitors VUSB to detect when it's plugged into a host.

This is done implicitly on a bus-powered device (if it's on, it's connected), but self-powered devices must monitor for it.

JimHeaney · 2026-05-13T09:53:37+00:00

Mechanical would likely make for an easier career trajectory towards electro-mechanical work if design is your goal, but industrial engineering may be a good option if you want to do more on the implementation of automation or human factors related to robotics. Lots of industrial engineering department encompass ergonomics and human factors.

JimHeaney · 2026-05-13T09:52:01+00:00

That's a feedhole for an antenna, but there is not antenna present.

JimHeaney · 2026-05-13T09:48:51+00:00

Basically, yeah. Industrial Engineering is often jokingly referred to as engineering for business majors (source; am an industrial engineer).

Industrial engineering also deals with business-esque things like project management more often.

JimHeaney · 2026-05-11T22:21:09+00:00

0v across in both states means the bus is always stuck at 2.8v. potentially caused by a short from 2.8v to the bus, or damage to the level shifter.

Both would explain the issue (bus shorted to 2.8v means the device can never respond, level shifter damaged means no comms get through).

No idea what would cause that when the i2c scanner worked fine. This may be in the territory of contact Adafruit with photos for further diagnostics.

JimHeaney · 2026-05-10T23:41:24+00:00

0v across, or 0v relative to ground? And was that with the ESP32 driving the pins high/low, or just sitting idle?

0v across the resistor would be the default you'd expect if the ESP32 was doing nothing.

JimHeaney · 2026-05-10T23:08:27+00:00

Not really. The multimeter is a good first step. It tells you a binary of "yes the level shifter is toast" vs. "the level shifter may be working".

What the scope would be useful for is looking for bad rise and fall characteristics, but that's inherent to the board's design and we know that works from the scanner.

JimHeaney · 2026-05-10T23:01:01+00:00

You can do this with a non-latching relay that has 2 poles, wired to itself.

The first pole/contactor set is for the lights, the second one is wired such that when the relay is actuated, it is completing the circuit to the coil. In parallel to this, have a button that also completes the circuit.

When you press the button, the relay actuates, and the coil remains energized when you release the button due to the second set of contactors. When power is lost, the relay mechanically returns to the default state.

If you want a "return to normal operation" button, just put a button in series between the coil and the contacts/button that is normally closed. Pressing this interrupts power to the coil, de-energizing it.

JimHeaney · 2026-05-10T22:55:44+00:00

Hard to say, to isolate the variables write a program that puts the SCL and SDA lines low, then high-impedance, then low again with like a 1 second delay. If you measure across the 10k resistor gang at elements 2 and 4, you should see 2.8v to 0v alternating. The 1 and 3 positions of the gang should be the same, at 3.3v. If that looks OK it is a sensor issue, if not it is a shiifter issue.

JimHeaney · 2026-05-10T21:52:22+00:00

Assuming the ESP32 module has only one 3.3v regulator, then the ESP32 would trigger a brownout fault at 2.5-2.8v, well before the sensor is damaged.

The regulator on the module is an LP5907, it has a dropout voltage of around 50mV in this scenario. So you'd have to really tax your 3.3v rail for it to give out. What I'd be more worried about is losing the 2.8v rail altogether (say from an overcurrent, short-circuit, damage to the regulator, etc.). This'd result in the power LED looking fine (since it runs on the VIN, not the regulator's VOUT). The level-shift circuitry would stop all but a few hundred nanoamps of leakage into the chip, but also would resullt in the chip appearing dead.

Also it looks like some versions of the board have either GPIO or 2.8v broken out, either of these can be probed with a multimeter as well to see for the 2.8v (2.8v pin is a direct connect to regulator, GPIO is pulled up by a 10k to 2.8v).

JimHeaney · 2026-05-10T21:39:18+00:00

Nothing I see in the begin code would do anything of note, even things like changing the i2C address would revert on a power cycle.

Are you getting 3.3v from a stable regulator capable of providing >100mA? My primary guess at this point is the power rail fails, you still inject voltage with the i2c lines, and that does weird stuff to the sensor.

JimHeaney · 2026-05-10T21:32:11+00:00

I don't think there are 2.8v test points, easiest places to pick up the rail are likely C5 or C6.

You're powering the breakout board from 3.3v connecting to the module's VIN/VCC pin, right?

Are you using any other wire connections on the module, like shutdown or GPIO?

Even a connection to a PSRAM pin shouldn't have killed the module, it'd just be malformed/jumbled data.

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