Saturday, January 17, 2015

Better PC Sound Card Oscilloscope software (windows).

TL;DR - Visual Analyzer, PC Sound Card Oscilloscope software.  Nice spectrum analyzer.  Worth checking out.

Through a really good YouTube Post on using an SDR for Frequency Deviation Measurement on FM transmitters I learned about Visual Analyzer. I should probably do a separate post just on this.

Previously I used Xoscope on Linux and Zeitnitz Soundcard Oscilloscope (

I had also found, but not used Zelscope, Soundcard Oscilloscope and Spectrum Analyzer.

I originally got some pointers on sound card osclloscopes, from Virginia Tech's Introductory Electronics courses that were based on their Lab in a Box, so that students would have all of their own materials for doing the electronics work without having to be in a physical lab.   See:

Virginia Tech, Experiment 12, Calibrating a Sound Card Oscilloscope

I only went so far with sound card oscilloscopes, because shortly after I started experimenting, the Rigol DS-1052E oscilloscope became available within my budget.  I bought it for $400 direct from China.  The Rigol caused a little bit of a revolution in terms of oscilloscope availability and pricing.

That was all back in 2009 and 2010 when I started reading a lot more about electronics.  In December, 2009, I finally took the exams from my amateur radio license.  I passed both Technician and General with 100% and went back for the Extra Class at the next exam session.  I got one wrong on my Extra.

Of course, the interesting bit that got me here writing this today is that the RTL-SDR stick can be used as the analog (ok radio frequency) front end for a software oscilloscope, spectrum analyzer, deviation meter, etc.  Especially for those of us without much in test equipment.

Monday, January 12, 2015

Intel Atom (Avoton) Mini-ITX (NAS) Server Build Notes

I'm building a mini-ITX NAS style server using Intel's low-power Atom server chip, known as Avoton.  The highlights are 8 cores, 64 GB max memory, yet passively cooled, quiet and low power, 20W TDP.The system's idle power usage without spinning disks is only 14 Watts. This makes it ideal for a SOHO file server, NAS server, lab box, etc.

The system I'm assembling resembles iXsystem's FreeNAS mini.  The main difference is that I went with the Supermicro motherboard instead of the ASRock motherboard.  I'll compare the two motherboards later and/or in a separate blog post.  However, I'll summarize my decision as The ASRock is better if you are going for a pure storage (NAS) box.  I went with the Supermicro as a better general purpose system with USB 3.0 ports and 4 x GbE ports.


Case and Power Supply

One of the most difficult decisions was trying to find a good case and power supply.  There is a lot of poorly designed cases.  There aren't many reviews for mini-ITX NAS-style cases. Through the reviews that are available I found one good choice which is also the same case that iXsystems uses for the FreeNAS Mini, the Ablecom CS-M50. Unfortunately the Ablecom isn't sold in the US directly.  It is primarily sold to OEMs in large quantities. I stumbled around for a while until a kind person clued me in that Supermicro sells the Ablecom CS-M50 as the Superchassis 721TQ-250B. It is even linked from the page for the A1SAi-2750F motherboard and I didn't notice it or assumed it would be yet another crap case.

The summary is the Ablecom CS-M50, aka Superchassis 721TQ-250B is a very nice case with real hot swap drive support. The most detailed reviews are actually for the FreeNAS Mini.  You can also find some reviews searching for the Ablecom CS-M50.

The one problem so far is that the front panel USB ports are USB 2.0.  The A1SAi motherboard has header connectors for USB 3.0, which use a different style header connector.   Currently, I've got no front panel USB ports. I've emailed Supermicro support.

Other People's Builds

Here are some of the sources that I used in making my decisions:

To Do

  • Determine what combination of hypervisors and operating system
    • Linux Host + VirtualBox
    • Linux Host + KVM
    • VMware ESXi
    • FreeNAS native FreeBSD
  • Solve Front Panel USB port connectivity problem:
    • Ideally there is a board from Ablecom, Supermicro or someone else that will give me USB 3.0 front panel ports.
    • Alternatively, an adapter cable that gives me USB 2.0 ports would be preferred.

Things I've Learned

  • The Supermicro 721TQ-250B case is the same as the Ablecom CS-M50 and is available at retail in the US.
  • The AST2400 IPMI BMC controller with fully integrated keyboard, video, and mouse, iKVM is very nice. I could have configured the system out of the box without ever attaching a monitor to.
  • The Supermicro/AST default Username and Password for IPMI is UPPER CASE and CASE SENSITIVE.  I mistakenly thought I couldn't access the BMC until I configured it through the BIOS.  The whole problem was the the default username and password were both all upper case.
  • As a result, the system is INSECURE out of the box. Change your IPMI/BMC username and password from the default as soon as possible. 
  • IPMIView from Supermicro/AST is pretty nice. It is a standalone Java Application. However the web browser interface is just as good or better for a single system.
  • The BIOS watchdog feature causes the system to be reset every 5 minutes.  Nothing is logged to the event log.  Don't set it, at least until you understand how to use it.   I think the Linux kernel is setting the hardware watchdog. 
  • An improperly seated SO-DIMM, caused the system to hang at BIOS POST, with the code B4.  However there were no beeps and I couldn't find a description of text error codes. The manual only gives the beep codes.
Hopefully this info will help others.