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2016 November 15

Not getting a new MacBook Pro

Filed under: Uncategorized — gasstationwithoutpumps @ 21:40
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My old MacBook Pro (late 2009 model) has been failing for the past few months (the SD card reader no longer works, the battery only lasts about 2–3 hours, the case is now failing in a way that exposes the electronics, …), and so I was planning to get a new MacBook Pro when the 2016 models came out.

But having seen the descriptions of them online and the prices, I’m not very enthusiastic about the new laptops.  One problem is the USB-C-only approach.  This video sums up my attitude:

(My wife says that the real story of the video is a restaurant worker who lost all the paella pans to the tide after leaving them on the beach.)

Other problems for the new MacBook Pro include the small sizes for the RAM and SSD drives  (my current laptop has 735GB of files on it and 8GB of RAM, so a new one would not be more capacity). Maybe I’ll wait a year to see if they can get a decent price/performance ratio on them.I’m also not excited about the low-travel keyboard, and the large trackpad might make it difficult for me to type, as I often rest the heels of my hands on the case, just a little outside the old, smaller track pad.  So the machine description did not make me want to rush out and spend a couple of grand on a machine that I may be unhappy with.

But my laptop is unlikely to survive another quarter, much less another year, so I’m faced with a bit of a dilemma, as I need a functioning laptop for giving lectures—particularly for demoing PteroDAQ and gnuplot.

I had recently bought the household a refurbished MacBook Air for travel (11″ early 2014), as my laptop is a bit too heavy for convenient travel, and my wife prefers a small laptop to an iPad (which we don’t have). Today, my wife suggested that I use the tiny MacBook Air for lecturing, and get another iMac as a desktop machine (we already have a mid-2011 iMac). The MacBook Air is sufficient for lecturing and travel—it has a couple of USB-A ports, so I can use flash drives or run PteroDAQ or the BitScope USB oscilloscope for lectures, and it has a mini-display port, so I can use my existing VGA dongle to connect to the classroom projector (which is VGA, not HDMI, according to the website of classroom media capabilities—I’d better double-check IRL).

If I decide to use the MacBook Air for lecturing, I can set it up over Winter break with all the software I’ll need and not worry about replacing my MacBook Pro for a few more months.

And then I probably will get an iMac. I can get much more machine for the money buying an iMac rather than a MacBook Pro, but I’ll have to think about exactly which iMac to get. Currently I’m leaning towards a 27″ retina display  model with an i7 processor, but I’ll have to look at prices and specs a bit more.  I’ll want a machine that will not cost more than about $500/year, amortized over its usable life, and preferably a little less.  There is a tradeoff between getting a high-performance machine that will be usable for a year or two longer, or a refurbished machine that has somewhat lower performance but can reasonably be replaced sooner.

2016 August 5

Digilent Analog Discovery 2 USB Oscilloscope

Filed under: Circuits course — gasstationwithoutpumps @ 14:12
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I have recently learned about a new USB oscilloscope, Digilent’s Analog Discovery 2, which seems to be a step up from the BitScope BS10 USB oscilloscope that I currently own. Digilent’s offering has differential inputs, 14-bit ADC (instead of 8), 100MS/s (instead of 40MS/s), and much nicer-looking user interfaces (no more black background!).  It costs a little more ($279 vs. $245, both costing more to get BNC connectors for higher-speed oscilloscope probes), but Digilent has an academic program that reduces the cost to only $179, so that even with an extra $20 for the BNC adapter and $20 for scope probes, the price is still lower than the BitScope.

I’m considering getting the Analog Discovery 2 scope (if I qualify for the academic discount), but I’ll probably wait until I replace my laptop.  The free Waveforms 2015 software runs on a wide range of Windows versions, but only 10.9 or newer on Mac OS.  (It also runs under some versions of Linux).  I’m still running Mac OS 10.6.8 on my laptop, and I don’t want to “upgrade” to a newer OS on the old hardware—I’m planning to replace the laptop this year, but I’m waiting to see whether Apple comes out with a usable MacBook Pro in 2016, or whether they’ve gone all in for connector-less laptops, in which case I’ll probably have to switch to a cheaper, but clunkier Linux laptop.

One of the things I like about Digilent’s marketing is that they have a very thorough reference manual online, which goes through the design of the hardware, explaining the schematics and some of the design choices for what chips they used. The online reference manual for Waveforms 2015 seems decent, but not as thorough as the hardware manual.

I’m curious whether any of my readers have tried the Digilent USB oscilloscopes.

2015 March 31

First lab for Spring

Filed under: Circuits course — gasstationwithoutpumps @ 21:50
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I had a very long day today (as I expect all Tuesdays and Thursdays to be this quarter).  It started out with me in a panic, because I had gotten a message late yesterday afternoon, telling me that the parts kits for the course were not ready yet, but not telling me what was available, so I didn’t know whether I’d be able to run today’s lab or not. I thought I probably would be able to do the essential parts, because the main part of the lab was soldering headers onto the KL25Z boards, and the boards and headers were ordered from Digi-key, which has very fast delivery (thanks to their almost instant packing of parts for shipping and their using the post office rather than FedEx, which has been unbelievably slow this year).

I went into work a bit early this morning to check on what parts were available (after a night of thinking about what labs I could do if the KL25Z boards were not available—pretty much only the thermistor lab scheduled for next Tuesday, and that takes about an hour of setup to prepare the lab and have hot water and ice water available).  As it turns out, the person who had informed me of the incomplete parts list had sent out a spread sheet with the information—he’d just forgotten to CC me on it. The KL25Z boards, the headers, and the USB cables were all available, so we could do the main part of the lab.  We couldn’t do the unpacking of the parts kit and identifying parts, but that can happen later, as the parts come in.

For Thursday’s lab, it would be good if they had their breadboards, resistor kits, and electrolytic capacitors—but I don’t know whether those will all be ready by then (the resistor kits haven’t all arrived yet).

Once the boards arrived, I started part of the class soldering (we only had 6 soldering stations, two of which were not very functional, despite my request 2 years ago for enough soldering irons for the 12 benches).  While some were soldering, the rest were downloading the PteroDAQ software and trying to get it to work on their machines.

The soldering went well, with one serious exception.  One student soldered in the connectors on the wrong side of the board, and neither the group tutor nor I noticed in time (and we could have, because we had looked at the board and just not noticed). We helped remove the connectors (removing a 2×10 female header from a board is a lot of work), but the student did not have enough time to get all the connectors replaced by the end of lab.  The tutor will provide some supervision at another time before Thursday’s lab to finish up.  All the solder joints looked clean—I saw neither bridges nor voids.  I did send several students back (more than once) to reheat cold-solder joints, but in the end all the students had good connections.  Since only 2 or 3 of the 32 students had ever held a soldering iron before, I think that getting each to make 64 good solder connections is a pretty positive outcome.  They’ll have 3 more labs this quarter where they will have to solder (their own designs, not just headers), but I think that they’ll approach those labs with more confidence now.

The PteroDAQ downloads were not quite as successful.  I think that everyone managed to get the MBED.ORG download software installed, and transferred the daq_kl25z.bin executables to the KL25Z boards. Most (all?) got PteroDAQ working with the lab computers. But few, it any got PteroDAQ working on their own machines.  There were three classes of problems:

  • On Windows 7 machines, I forgot how to use the mbed-usb-windows.inf files to install Windows drivers for the USB port on the KL25Z board. I looked it up after class before going home and found a page about installing Windows drivers for Arduino boards that seems to have all the right instructions (but use the .inf file in the PteroDAQ extras directory, not arduino.inf):
  • On Windows 8 machines, I don’t know whether the same approach will work, but I hope that some of the students will try. The approach given in the MBED handbook did not seem to work, but I’m not very comfortable with Windows, so I may have missed something obvious to a serious Windows user.
  • On Mac OX 10 machines, we had two problems:
    1. OS 10.10, 10.10.1, and 10.10.2 were not willing to write to the MBED device. This seems to be a known problem that the MBED user community is pretty upset about. The MBED developers have been working (slowly) on the bug since last October, with patches for only a few of their many supported boards (not, so far as I can see, the KL25Z).  There are claims on the developer forum about the bug that OS X 10.10.3 beta finally fixes the bug, but no one in their right mind would suggest that students install Apple beta code on a machine that they plan to use for anything. A student was going to enter an “issue” ticket on the PteroDAQ website, but it doesn’t seem to be there yet.
    2. If the Windows 7 machines in the lab were used to put the daq_kl25z.bin onto the boards, then OS 10.10 seemed to work ok (a student got it running), but OS 10.10.1 and 10.10.2 machines failed.  The problem seemed to be with Tkinter: the selection of the port for the KL25Z was not sticky—it deselected itself within a second of being selected. Some of the students had freshly downloaded versions of Python 3.4, so the problem doesn’t seem to be with old code, though I suppose a Tcl/Tk incompatibility with Python is possible—I didn’t have any of the students try re-installing Tcl.  I hope that a student with an OS 10.10.1 or 10.10.2 machine will post an issue ticket about this issue on the PteroDAQ website also.

    I’m now very glad that I did not “upgrade” my old OS 10.6.8 Mac to 10.10 on my 2009 MacBook Pro—it seems that I would have broken many of the things that I rely on my Mac for. Perhaps I’ll wait until I get new a new laptop before “upgrading”—and I won’t buy a new Apple as long as they don’t work with MBED, even though my current laptop has a very sick battery and is beginning to show its age. (I have no intention of buying a MacBook with only one USB-C port, either: I routinely use the power cable, the ethernet port, the firewire port, the display port, both USB ports, and the SD card port, and often use three or four of these at once.)

It would be really nice to have installation instructions with PteroDAQ—I forgot some steps of how to do the installation on Windows (the driver installation), and it would be nice to have a written description of the steps for a Mac that I could just point students to, rather than walking them through it.

I set up a mailing list for the class this evening, and I hope that students who manage to get PteroDAQ working on Windows 8 or OS 10.10.1 or 10.10.2 will share the information.

2013 August 15

Adding RAM to my MacBook Pro

Filed under: Uncategorized — gasstationwithoutpumps @ 17:21
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I’ve been having trouble with running out of RAM on my MacBook Pro laptop lately, resulting in huge delays as everything is swapped out to disk. There are two reasons for this:

  1. Firefox is a memory hog, especially if Flash has ever been run.
  2. I’ve been running some very poorly written programs that read in an entire data set to a NumPy array before processing the data (rather than processing the data as it is read).  I know that this program is terribly written, because I wrote it—I needed a quick and dirty test of an algorithm in Python before writing a better implementation with better I/O (which will probably be in C or C++).

My MacBook Pro was bought in mid-2009, only 4 years ago, and I’m not quite ready to replace it.  But I’ve been finding the 4GB RAM in it rather limiting (though not as limiting as the 2kB RAM that my first computer had, or the 128kB of my first Mac).

This week I finally decided to splurge and replace the RAM with (2×4GB) memory cards.  I looked on the web to find out first what Mac I had (using How to Identify MacBook Pro models), then what sort of RAM I needed.  The Crucial web site is a good one for identifying what RAM you need, though there are many others.

Crucial recommended 8GB Kit (4GBx2), 204-pin SODIMM, DDR3 PC3-8500 memory module with 1066MHz and CAS latency of 7 and I confirmed the specs with the Apple technical specs web site for my Mac.

I then spent some time looking for cheap RAM that met the specs.  Some of the cheapest RAM was on various e-Bay stores, but they did not give the manufacturer of the RAM, and I was not willing to risk off-brand parts for $5 in savings—I’ve been burned on eBay before.  I found a reasonable price for name-brand RAM on Amazon, which turned out to be for Crucial RAM that was cheaper than buying direct from Crucial—only $65, including shipping.

I ordered the RAM on Sunday 2013 Aug 11, it was shipped on 2013 Aug 12, and  it arrived today (Thurs 2013 Aug 15).

Today I followed Apple’s instructions on MacBook Pro: How to remove or install memory to install new RAM. It was very straightforward, and I didn’t even drop any screws. The installation does require a small Phillips screwdriver, but no other tools (unlike some of the early Macs, that needed special tools to open the cases).  Replacing RAM is well within the capability of the average user—at least, the average user who knows how to use a screwdriver.

So now I have an 8GB laptop instead of a 4GB one, and I should get a little less swapping.

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