@Anna’s - Posts

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Anna Norris — Fri, 26 Jun 2026 00:00:00 +0000

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Anna Norris — Sun, 21 Jun 2026 00:00:00 +0000

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Anna Norris — Sat, 13 Jun 2026 00:00:00 +0000

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Anna Norris — Wed, 27 May 2026 00:00:00 +0000

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Anna Norris — Fri, 10 Apr 2026 00:00:00 +0000

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Anna Norris — Sat, 04 Apr 2026 00:00:00 +0000

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Anna Norris — Thu, 19 Mar 2026 00:00:00 +0000

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Anna Norris — Thu, 05 Mar 2026 00:00:00 +0000

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Anna Norris — Sat, 21 Feb 2026 00:00:00 +0000

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Anna Norris — Sun, 01 Feb 2026 00:00:00 +0000

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Anna Norris — Fri, 11 Jul 2025 19:28:58 -0400

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Anna Norris — Mon, 19 May 2025 14:43:21 -0400

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Anna Norris — Tue, 25 Feb 2025 15:49:59 -0500

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Anna Norris — Mon, 17 Feb 2025 17:34:18 +0100

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Anna Norris — Sun, 16 Feb 2025 20:00:00 +0000

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Anna Norris — Sun, 24 Nov 2024 09:44:08 -0500

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Anna Norris — Sun, 20 Oct 2024 10:36:31 -0400

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Anna Norris — Thu, 03 Oct 2024 07:57:16 -0400

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Anna Norris — Wed, 14 Aug 2024 10:07:47 -0400

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Anna Norris — Tue, 02 Jul 2024 12:06:27 -0400

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Anna Norris — Tue, 25 Jun 2024 09:26:47 -0400

In the late Eighties, when walking through the gorge was her regular commute to work, Betsy noticed some stakes in the ground. She assumed they were going to be building a new walkway, and called Cornell, who owns the land, to learn more. What she learned was that it wasn’t a walkway or enhancement to the natural area: it was an eight-story supercomputer research centre that was going to plunge right into the gorge.

“I told her, Betsy, the stakes are already in the ground. There’s no way you can stop this building,” said Dick. But there was a way: the federal funding for the building required public consultation. The building was a rush job, and the public hearing hadn’t happened yet. All summer Betsy set up a table on the footbridge in the gorge with information about the land and the planned building. She gathered thousands of signatures on a petition and finally, after a public hearing which went long into the night with residents voicing their opposition, Cornell scrapped the plans for the building to extend into the gorge and redesigned it to stand back from the edge of the valley.

“What’s funny,” said Betsy, “Is that a lot of the people who were in favour of the building at first actually thanked me after. The people who worked in the building hadn’t gotten to be part of the planning of the original design, and they said later that the redesign was much better for them.”

“Before that,” said Dick, “She was Dick Darlington’s wife. After, I was Betsy Darlington’s husband.”

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Anna Norris — Tue, 14 May 2024 19:12:36 -0400

Using TI Code Composer Studio to program the MSP-EXP4432E401Y on Linux

Anna Norris — Sun, 05 May 2024 15:10:45 -0400

Although I have a Windows partition installed on my laptop, using it means rebooting the computer and, inevitably, running into some rage-inducing reminder of why I do not use Windows.

For my microcontroller class this semester, we were given instructions on creating and flashing programs to the Texas Instruments MSP432E4 micro using the Windows-only Keil IDE. Since I didn’t want to be left behind in the class demonstrations, I didn’t get too far in investigating Linux alternatives besides the vague impression that I might need to write my own makefiles in order to use example code with the GNU ARM toolchain. Wrong!!! As it turns out, Texas Instruments provides a free IDE for its boards that is available for Mac, Windows and Linux… and now that the class is over, I’ve finally figured out I could have been using it all along.

So, here’s a walkthrough of setting up to program the MSP432E4 on Linux. (I’m on Mint, though I doubt there’s much here that’s terribly distro-dependent.)

First, install the Software Development Kit. This isn’t the IDE, it’s a collection of files that the IDE (or you, if you’re a makefile wizard) will use. As of May 2024, the link to get the SDK for the MSP432E4 is here.

When the SDK installer finishes downloading, you will probably need to allow it permission to execute. Right click on it and choose properties > permissions > allow executing file as program, then run it. The setup wizard will ask where you want to install it; probably just keep the default location, which is a folder called “ti” in the home folder of your local user.

Next, download CCS from here. I chose the offline install for Linux. It comes in a compressed folder, so extract it. Inside that folder is a file which begs you to read it first, which will tell you to run the executable.

That installation wizard will check the dependencies on your system. I had a missing dependency, libpython2.7.so.1.0, which was fixed by running

sudo apt-get install libpython2.7
sudo apt-get install libatlas3-base

if your distro doesn’t use the Debian apt utility, or you have different stuff missing, you’ll need to look up how to correct it before continuing.

After all the dependencies are OK, it will suggest installing itself inside of the ti folder that the SDK already made, so do that. Choose “Custom installtion” and select “SimpleLink MSP432 low power + performance MCU”. Keep the default debug probe selected, I guess, idk what the others are.

When the installer is finished, it tells you to run the driver install script before anything else, so go to the file path it provides and run sudo ./install_drivers.sh. Mine worked fine without rebooting but it will warn you some distros need you to reboot for it to take effect.

You can now launch the IDE from the icon in the ti/ccs12.x.x folder! The first time you launch it, it will ask you what you want to use as a workspace directory. I already have a folder I’m planning on keeping all my microcontroller stuff in, so I chose that one and selected “Use as default and do not ask again.”

Time to try it out with some example code from 2DX3! I downloaded a fresh copy of the provided Studio 4A example code from Avenue. Because it was created using the Keil IDE, it has some extra files and directories generated by Keil that aren’t needed.

From the Getting Started window of CCS, choose New Project. In the wizard that opens, make sure you set the correct board, and since we already have a project with a main function, choose to create an empty project with no main.c file.

The new project should now be visible in the Project Explorer window at the left side of the screen. Right-click on the project name and choose “add files”. Add all of the .c and .h files to the project, and then confirm that you would like to copy them instead of just linking to them.

Press the hammer icon to build the project, and the arrow going into a folder to flash it to the board.

That’s it! Since this code is flashing an external LED from PN2, I attached the circuit to test it:

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Anna Norris — Fri, 03 May 2024 13:04:40 -0400

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Anna Norris — Tue, 09 Jan 2024 16:42:05 +0000

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Anna Norris — Mon, 08 Jan 2024 09:05:41 +0000

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Anna Norris — Sun, 07 Jan 2024 15:56:00 +0000

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Anna Norris — Sat, 06 Jan 2024 17:20:13 +0000

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Anna Norris — Thu, 04 Jan 2024 16:13:44 +0000

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Anna Norris — Tue, 02 Jan 2024 14:22:09 +0000

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Anna Norris — Sat, 30 Dec 2023 14:35:26 +0000

Physical intuitions for impedance matching and critical damping

Anna Norris — Sat, 23 Dec 2023 15:52:33 +0000

Impedance matching is the idea that if you want to deliver maximum power to a load, the amount that the load “pushes back” on the power source should be equal to (the complex conjugate of) the amount the rest of the circuit pushes back. If you were writing a textbook, you would convince your readers like so:

But what if you weren’t writing a textbook, and wanted to convince someone who was planning on simply getting up and walking away the moment any of those libertine little d’s or, god forbid, the imaginary unit (or the jmagjnary unjt, as the case may be) made an appearance?

Then you could say, imagine you are playing that game where you put a jump rope on the ground and send a pulse through it. You want to try to make sure that the pulse that reaches some given point on the jump rope is, as precisely as possible, exactly the same as the pulse that leaves your hand. You have two choices.

First, you could use two jump ropes tied together, where the two ropes have different thicknesses, or might be made of different materials, or maybe one of them is that beaded kind that hurts like a #!%$ when you hit yourself in the ankle with it:

Or your second option, you could just use one really long jump rope, that has the same thickness and material used throughout.

It’s intuitively obvious that, if there’s a possibility of you being asked to transmit that as-faithful-as-possible pulse to the far side of the rope, you’re way better off with the one long rope. If that isn’t obvious, it’s obvious that you can go buy some jump ropes and try it out for yourself. Of course, the rope that has the same “impedance” throughout is going to transmit the pulse more faithfully, while the tied-together bit is going to muck things up.

A piece of physical intuition that was less obvious to me at first was that for critical damping. In one assignment, we simulated in software and built in meatspace three different versions of an LRC circuit: an underdamped one, overdamped one, and then figuring out what resistive value to swap in to get it critically damped.

Of course, an underdamped circuit oscillates, as seen in both the simulation and the oscilloscope hooked up to a breadboard:

And an overdamped circuit decays exponentially:

A critically damped circuit– i.e., one where the characteristic equation of the circuit has repeated roots, and there is only one natural frequency– decays faster than an overdamped one:

Why, though? When the words are spoken, it sounds like the thing called “overdamped” should do the thing called “decaying” the fastest. The math, of course, is entirely clear: with repeated roots to the characteristic equation, the solution to the differential equation has an exponential decay term multiplied by the independent variable of time, while the overdamped case has no such thing. So of course the critically damped case has to decay faster. But that’s just a property of multiplication, not a good explanation (and we lost the no-libertine-d’s-or-i’s-or-j’s observer some time ago.)

The physical intuition, then: imagine you are dropping a little ball into a glass of some kind of fluid. Your goal is for the ball to come to rest on the bottom of the glass– equilibrium– as quickly as possible. If the fluid is not sticky enough to slow down the ball before it hits the bottom, it will bounce (underdamped.) If the fluid is sticky, it will slow down the ball enough that it won’t bounce– but there is a point of stickiness beyond which any extra stickiness isn’t actually helping to prevent bounces, it’s just delaying the ball reaching the bottom. Just the right stickiness to prevent bouncing, without slowing down the ball’s progress more than necessary, is critical damping; excessive stickiness is overdamping.

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Anna Norris — Tue, 05 Sep 2023 00:52:04 +0000

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Anna Norris — Sat, 26 Aug 2023 00:04:29 +0000

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Anna Norris — Mon, 13 Mar 2023 00:38:00 +0000

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Anna Norris — Sat, 15 Oct 2022 16:45:00 +0000