mini digital storage oscilloscope review

I just got in the decidedly-cute DS203 Mini DSO (digital storage oscilloscope), weighing in at a mere 80 grams. We can reasonably guess from MiniDSO.com’s website that English is a second language for them. From what I understand, this is an open-source project so it will be fun to see what I can do with this.

SainSmart
K1, K2, K3, K4 & NAV A, NAV B across the top

Open Source

From what I’m reading in an online PDF, you can tether this to a PC and it appears as a USB drive, allowing you to make some modifications to the system itself. There appear to be examples for updating the splash screen logo and downloading/updating the application itself. Since this is likely some sort of Linux as the operating system then that will mean that I might be able to hack apart the update to find out what’s inside.

Precision

Looks like there are six adjustable potentiometers “under the hood” to allow you to calibrate it for accuracy. Most full-sized scopes have this feature but usually only about two of these adjustments, to be honest.

Accessories

It was fully assembled in the box although the online PDF suggests that there was a time when the customer was asked to fully put it together. This one included two probes (1X, 10X) which is pretty generous given that they can be as much as $30 each. It includes a small hex wrench for opening the back (access to those potentiometers). And finally, there was a tri-fold card with the barest of instructions possible. Here’s an example of a third of the instructions:

Turn on the power, enter the main page of the oscilloscope. Place in the standard signal (e.g. square wave 1 KHz, Vpp = 5V), insert X1 probe’s MCX end to CH A or CH B, and the probe to “WAVE OUT”. Check if the measurement value and the standard value are equal, calibrate if different.

Okay, I know enough about oscilloscopes to know what they mean here. I’ll translate this into English-geek for you:

Connect the X1 probe to the CH A connection, power on the oscilloscope and wait for the main screen to appear. Remove the probe’s cover to reveal the bare tip, putting this into the center of the  “WAVE OUT” port. Press Key 4 until the side menu is selected then use NAV 2 to select V1 from the options. Use NAV 1 to adjust the horizontal line until it coincides with the top part of the square wave, noting the voltage—as now measured—at the bottom of the screen. If this voltage is different than the reference 5.0V from the signal generator, then calibrate the meter by following these steps…

etc

At least that is the standard routine on a full-sized oscilloscope. I guess what I’m trying to say here is that the online PDF and tri-card documentation are pretty laughable and aren’t enough for the average person to learn how to use it.

On-screen Menu

The menu is pretty difficult so far. It’s clear that NAV A and B are used in selecting different values and moving from one place to another. K4 appears to move between the top set of menus to those down the right side of the screen.

Progress

After two full evenings playing with the interface, I’m beginning to understand some of the strange logic. Some of the hidden functionality is found when you press down on either the NAV A or NAV B sliders. It’s lost on the average person that these left/right sort of controls actually can be pressed as well. This opens up the missing features which were formerly lost on me.

So now, I can put an output wave on the screen (CH A–inserted probe to WAVE OUT), adjust the signal to a square wave of 20 microseconds in width, add a single reference voltage V1, hide V2 (and Channels B/C/D), adjust the T1 and T2 reference lines to match up to the waveform’s leading/trailing edges and then reference the delta at the bottom of the screen. Given the complexity of this as compared to the absence of a working manual, I’d call that rocket science.

The next step will be to attempt to calibrate it with a known good 5V power supply which I’ve just adjusted, having measured that with a good-quality multimeter.

Thoughts

I’m torn between moving ahead now with my own work and writing a useful how-to manual for this oscilloscope. It’s a shame that someone’s not written a good tutorial yet for this.

Update

And of course, I began working on rewriting a useful manual for this.

apple: hiding the truth

One business dictionary defines transparency as “a lack of hidden agendas or conditions, accompanied by the availability of full information required for collaboration, cooperation and collective decision-making”. Perhaps Apple could do well by re-reading that statement and the two emails that they sent me this week, in reverse order (since it’s funnier that way).

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My New (Used) iPhone 5

I’d recently purchased a used iPhone 5 from a co-worker. He’d indicated that it had a problem with phone calls and had decided to upgrade to the latest phone Apple makes. So he was left with the iPhone 5 and I offered to buy it from him on the cheap since I do phone development and I knew that I could put it to good use.

Fast-forward a few weeks and I decided that my Android-based phone was really churning through the battery at a fair rate (compared to the iPhone) and so I thought I’d get a cellphone plan switch. I paid a few months in advance without thinking twice about it only to find that later when I’d gotten home, the iPhone 5’s microphone and speakers all worked great except during a phone call. Obviously, the phone had a problem of some kind.

Apple’s Support Forum

Here is the Apple support thread, in case you wanted to read along. It looks like countless people are having the same problem with their phones, too. At first I read all these and realized that nobody really knew what was going on with their phones. Like me, they were stuck with a mostly-useless piece of hardware with respect to making or receiving calls.

I took it to the cellphone carrier vendor and left it with him for an hour or two. He reset the phone and upgraded the firmware or similar but was unable to help out.

Someone on youtube had indicated that they’d thoroughly cleaned the microphone and speaker holes so of course I gave this a try. It didn’t help, of course.

I verified that all three speakers and the microphone all worked with other apps. I deduced that there might be a connectivity issue.

Inside the iPhone

Given that I have the proper tools for such a task, I decided to take it apart. Apple uses a pair of tiny “Pentalobe security screws” (Apple’s nomenclature) to secure the case of the iPhone series. I guess they think that the market won’t just make the appropriate screwdrivers and sell them to the public.

Once inside, I re-seated the various connections that could have caused the problem. I then re-tested but the problem still persisted. On a hunch I decided to twist the phone along its length and this immediately allowed the phone portion to work!

The Underlying Cause

Everything inside a phone like this is necessarily tiny and modular. As such, Apple relies upon each module to make an electrical ground connection against the outside of the case. A little twist and that connection is lost.

Another compounding problem is the nature of batteries of the type used in cellphones. They are prone to swelling and contracting over time and with each charging cycle. Apple appears to know all about this. In fact, it’s as if they’ve compensated inside the phone by allowing a fair amount of expansion room for the battery itself. One could suggest that there’s too much space since the sparcity inside just promotes more flexibility and this leads to losing electrical ground in those components I spoke about earlier.

The Fix

It occurred to me that a 3″x5″ card could be cut to fit and placed inside the iPhone’s body and should tighten everything enough so that those electrical connections would be made. Luckily, this was exactly what it wanted.

Letting the Community Know

As a good net citizen I decided to let others know what they could do to fix their own failing iPhones. I posted on that same Apple Support thread only to see that they don’t want you to know this.

Took my iPhone’s rear case off (carefully) and removed/replaced the three connectors that attach the screen itself, verifying absolutely that they were fully re-seated.  Then when putting everything back together I inserted a 3″x5″ index card (cut first to a 2-1/8″x3-1/2″ rectangle and then trimmed a portion from both long sides so that the outer snaps would clear it).

The thickness of the card is enough to tighten up everything inside so that all the connections mate up always.  It now works perfectly.  I have to think that the problem is due to occasional twisting of the phone along its length.  Old computer motherboards had the same problem, btw.

What I should have added to this on the Apple Support forum (but I can say this now) is that it appears that there is a systemic problem in the iPhone series with respect to electrical grounding.

Apple’s Response

Apple promptly deleted my post, citing that it contained “questionable advice”. Note that Apple themselves provide no advice for these users.

The problem here is that a good percentage of these users have no recourse but to purchase a new iPhone 6 ($550-$650). Apple decided that it’s in their best interest to hide a working fix to their older phones.

What Apple Should Have Done

Apple should have read the post, researched whether or not there was any validity in the claim and then should have posted something on the order of, “We are researching the issue and caution users that to open their phone would be to void the warranty. If we determine that there is an electrical grounding problem and you have registered your phone with us then we will contact you for a service call”.

If they had done something like this then they would have earned all our respect. The choice they made, however, just proves that Apple—for all their friendliness in their advertisements—are just a big corporation who doesn’t believe in transparency with their customers.