# Gas station without pumps

## 2020 January 11

### First week of class W2020

Filed under: Circuits course — gasstationwithoutpumps @ 21:16
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I’ve just finished the first week of class for BME 51A (Applied Electronics for Bioengineers), and it has been a rather hectic week.

First, I had about 5 people sign up for the class at the last minute (from 56 to 61), which drove the BELS staff to having to do a lot of expensive last-minute purchasing of additional items for the parts kits.  It also meant that when we handed out the parts kits on Tuesday, several of them were incomplete and so more items had to be handed out during the Thursday lab period.  Since getting their kits, 2 students have dropped taking us down to 59, and one other has told me that they might drop (assuming that they can get a coherent plan together for an independent study to replace the course).  This enrollment is less than last year’s 82 students, but still a fairly large number, given that the BELS labs can only accommodate about 24 students.  I’m using two lab rooms for the first section and one for the second section, and have hired 3 group tutors (one for each lab room and time) to work along with me in the labs.

The first week’s labs consist of soldering headers onto the Teensy LC boards and installing software: Python with SciPy (using the Anaconda install), gnuplot, Arduino+Teensyduino, PteroDAQ.  For the first time in years, everyone got their soldering done within the allotted lab times!  I don’t know what was different this year that made it work as it was supposed to.  One thing that helped a little was that when students soldered the male headers on the wrong side of the boards (which happens every year, despite all the written, pictorial, and verbal warnings I can give), I had them cut apart the male headers to unsolder, then gave them new male headers to solder on.

Software installation is always a problem, because students are attempting to install on a variety of platforms, and something is always incompatible. Here are some problems that came up this year:

• Gnuplot on old Mac OS X systems would not install with homebrew, as qt could not be installed—it insisted that you needed the full Xcode (not just the command-line subset), but Apple will not provide the full Xcode for such old, unsupported systems.  There may be already compiled versions of gnuplot for these old systems, but I have not gone looking for them. I’m not sure what to recommend to these students, other than updating to a system that Apple still supports.  I can’t recommend updating to Catalina, as they will lose all 32-bit apps, some of which will never be ported to newer versions of macos (for example, I lost access to Finale Notepad, which is no longer available on Macs—probably because Apple makes it so very difficult for third-party software developers to maintain their code).
• Gnuplot on new Mac OS X systems installs and runs, but produces bad PDF files.  The workaround for this was posted at https://stackoverflow.com/questions/57698204/gnuplot-pdf-terminal-exhibits-font-issues-on-mac. The answer to that stackoverflow question had two lines to fix the problem:
```brew uninstall --ignore-dependencies pango
brew install iltommi/brews/pango
```

The problem is that the default homebrew “bottle” for gnuplot points to a broken version of pango, and you have to remove that version and install an older version.  This one I knew about, because it had bitten me when I was trying to finish the book in December.

• The standard Arduino+Teensyduino installation fails on macos Catalina (10.15). I knew about this one also, as I had tested the PteroDAQ install after I had “upgraded” to Catalina (which broke nearly everything).  The workaround is a beta release of Teensyduino (currently https://forum.pjrc.com/threads/59030-Teensyduino-1-49-Beta-5), which is pointed to from the Teensyduino installation page, but many of the students with macos Catalina did not notice the pointer.  One nice feature of the Teensyduino beta release is that it includes the Arduino IDE, so that you don’t need to install Arduino first.
• The PteroDAQ GUI seems to be crashing on macos Mojave (10.14)—logging the user out when they try to run “python daq” as usual.  I think that this may be a weird filesystem thing, as it seemed to make a difference whether PteroDAQ had been cloned from GitHub or downloaded as a zip file, and whether the files were on the hard drive or on a Google Drive.  The only thing that seemed to work consistently was to clone the files from GitHub onto the hard drive of the laptop, then run the app that is in pterodaq/extras/maclauncher/ .  Why the launcher app works, when invoking “python daq” directly from a terminal results in logging the user out, is a mystery to me.
• On macos Catalina, PteroDAQ can’t find the board if it is connected to the laptop through a USB2 hub connected to a USB3 port (I ran into this problem on my laptop before classes started also).  Apple has once again scrambled their USB stack, and USB Serial no longer seems to be visible through a USB2 hub (though the USB device is visible, the serial interface does not seem to be).  This hasn’t caused a problem for any students yet, as direct connection to a USB3 port works ok, and connection from hubs on USBC ports seems to be ok (probably because they are USB3 and not USB2).
• One student had trouble getting PteroDAQ to run on his Windows 8 machine, with the python program crashing on trying to access the list of ports.  No one else with Windows 8 was having trouble, and his machine was running extremely slowly (slower even than the ancient “Barbie” laptop that I used for testing Windows implementations of PteroDAQ), so I suspect he was having hardware or malware problems on his machine.

I think that nearly all the students got their software installed—at any rate, people left the lab early on Thursday and were not queuing up for installation help, as they had in previous years.  Only one student asked for installation help during Friday office hours (the one with the probably bad hardware or malware), and there were no requests on Piazza for help.  If I’m right that everyone got things installed, then we are well ahead of previous years.

On Thursday, before lab, one of the group tutors ran a tutorial session on $\LaTeX$, which about half the class attended.  That should help somewhat in the prelabs to be turned in on Monday.

Monday’s assignments will be stressing our grading system a bit, as we have a lot coming in, but I couldn’t schedule a grading session until Wednesday at noon.  I’m hoping that we can get both homework 3 and the first prelab graded before Thursday’s lab.  If necessary, we can just give a turned-in/not-turned-in grade for the first prelab, as they are turning in a more complete draft of the same prelab on Friday, but I’d much rather give them feedback so that they can correct mistakes before the Friday draft.

So far, the quiz and homework scores look pretty good, so I’m hopeful that this will be a high-performing class this year.  It would be really nice to give out more B+ (and even A-) grades and fewer C grades.  I’m keeping my fingers crossed (even though that makes typing the blog post hard).

## 2019 December 19

### Macos 10.15 Catalina vs PteroDAQ

I had a serious scare today.

First, I found out that the software for my Analog Discovery 2 was crashing on the MacBook Air that I will be using for lectures and lab next quarter.  It behaved normally at first and then crashed for no discernible reason after a couple of minutes.  I figured that the problem was probably related to the macos “upgrades” I had done recently, so I checked the Digilent website, and they had just posted a new version of the software last week, addressing the changes that Apple had made to their USB stack (which broke almost all 3rd-party software and a fair amount of Apple’s own software).  I downloaded the new version of Waveforms from the Digilent site and everything worked again.

But any changes to the USB stack are likely to break the code that PteroDAQ uses for finding what devices are connected, so I checked PteroDAQ with my usual setup.  The GUI for PteroDAQ did not list the Teensy board as it used to do, and PteroDAQ couldn’t run!  I spent a long time with ioreg trying to figure out how to modify macgetports.py to find the device again.  The Teensy board was visible as an AppleUSBDevice and AppleUSBInterface, but not as an IOSerialBSDClient as it used to be.  I could not figure out how to open it as a serial port!

Now my usual setup involves going through a USB 2.0 hub (in the Cerebrus cable), so I dug around in my drawer of parts until I found a plain USB-micro data cable.  Hooking up the Teensy board directly with that cable did show an IOSerialBSDClient interface, and PteroDAQ worked fine.  So the problem is just that connections through the USB 2.0 hub are not made the same way they used to be—the serial connection no longer is visible the way it used to be.

I’ll enter an issue for this on the PteroDAQ GitHub, but I won’t try to fix it unless it turns out that modern USB C-USB 3 docks exhibit the same problem.

## 2019 December 8

### Book Done!

Filed under: Circuits course — gasstationwithoutpumps @ 22:06
Tags: ,

I’ve posted the latest version of the book—the first version I think of as really completed, so I’m calling it Edition 1.0.

The book is available at https://leanpub.com/applied_analog_electronics/ now, but I won’t raise the price until Tuesday, as I announced last week.  I’ve already sent the students registered for the course coupons for a free book, and they have started picking it up.

The new book takes up 28.7MB and has

651 pages
335 figures
13 tables
509 index entries
155 references

The chapter on Design Report Guidelines is available free at https://leanpub.com/design_report_guidelines. If your students need some advice on writing from an engineering professor, this document may be of more use to them than many longer texts.

## 2019 December 4

### \$1000 royalties!

Filed under: Circuits course — gasstationwithoutpumps @ 08:51
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I’ve finally earned \$1000 in royalties on my textbook!  Thank you to all my purchasers—especially those who chose to pay more than the required minimum.

Incidentally, the royalties come to a little more than the expenses I’ve incurred in developing the labs for the book, but it’s a good thing that I have a salary and could use sabbatical time to write the book, as the royalties come to less than 50¢ an hour of writing (probably more like 20¢ an hour, once expenses are taken into account).

## 2019 December 3

### Applied Analog Electronics price increase coming soon

Filed under: Circuits course — gasstationwithoutpumps @ 21:18
Tags: ,

I’m about 3 days behind my original schedule, but I have now cleared all the to-do notes out of my draft of Applied Analog Electronics.  It will be ready to release when I have run the 62 $\LaTeX$ files through a spelling checker and have gone through and checked all the page breaks, figure placements, figure sizing, and overfull hboxes.  I expect this to take me 2–3 days, but I’m allowing myself up to a week to complete the task.

I’ll be increasing the minimum price for the textbook from \$5.99 to \$7.99 on 2019 December 10, when I’ll be releasing the new version of the book.  Students registered for BME 51A will be getting a coupon for a free PDF of the book at that time also.

Because Leanpub purchases entitle buyers to all future drafts of the book published through Leanpub, those of you who have already bought the book (even with a free coupon) can get the updated electronic copy for free.

Those of you who are still thinking of buying the book can get it cheaper if you buy it now, then get the free update when it is released.  The URL for purchases is https://leanpub.com/applied_analog_electronics

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