If you do any work with analogue signals at frequencies above the most basic audio, it’s probable that somewhere you’ll have a box of coax adaptors. You’ll need them, because the chances are your bench will feature instruments, devices, and modules with a bewildering variety of connectors. In making all these disparate devices talk to each other you probably have a guilty past: at some time you will have created an unholy monster of a coax interface by tying several adaptors together to achieve your desired combination of input and output connector. Don’t worry, your secret is safe with me.
Fancy measurement gear is often expensive to buy, but some bits of kit are entirely DIY’able if you’re willing to put a little work into the project. [Christer Weinigel] needed to get some measurements of a differential clock signal that was ticking away around 500 MHz. El-cheapo probes aren’t going to cut it here. They won’t have the bandwidth and most off-the-rack probes are single-ended, that is they’re referenced to ground. [Christer] needed the difference between two balanced signals, neither of which is grounded. In short, [Christer] needed a high-frequency active differential oscilloscope probe, and they’re not cheap. So he built one himself.
The circuit in the probe is really just an instrumentation amplifier design with a modified input stage and a 50 ohm output impedance. (See this article on in-amps if you need to brush up.) With higher frequencies like this, it’s going to be demanding on the op-amp, so [Christer] spent some time simulating the circuit to make sure it would work with his chosen part. Then he made up a bunch of PCB designs and had them made. Actual results matched fairly well with the simulation.
With some minor tweaking on the input damping resistors, he got a tool that’s dead flat up to 300 MHz, and totally usable up to 850 MHz. If you tried to buy one of these, it’d set you back the cost of a few hundred lattes, but this one can be made for the price of one or two if you get the PCBs done cheaply. Of course, the design files are available for your own use. Kudos [Christer].
Edit: By total coincidence, Bil Herd just posted a video intro to differential signals. Go check it out.
And thanks to [nebk] for the tip!
Intel have a developer board that is new to the market, based on their Quark (formerly “Mint Valley”) D2000 low-power x86 microcontroller. This is a micropower 32-bit processor running at 32MHz, and with 32kB of Flash and 8kB of RAM. It’s roughly equivalent to a Pentium-class processor without the x87 FPU, and it has the usual impressive array of built-in microcontroller peripherals and I/O choices.
The board has an Arduino-compatible shield footprint, an FTDI chip for USB connectivity, a compass, acceleration, and temperature sensor chip, and a coin cell holder with micropower switching regulator. Intel provide their own System Studio For Microcontrollers dev environment, based around the familiar Eclipse IDE.
Best of all is the price, under $15 from an assortment of the usual large electronics wholesalers.
This board joins a throng of others in the low-cost microcontroller development board space, each of which will have attributes that its manufacturers will hope make it stand out. Facing such competition the Intel board will have to be something rather special to achieve that aim, so why should it excite your interest? We would point to the low price, the x86 code if that is your flavour of choice, and the relatively tiny power consumption.
Stepping back from the dev board for a moment, consider this processor as an illustration of technological progress in semiconductor fabrication. Over twenty years ago this chip’s Pentium ancestor ran on 5 volts and got so hot you could fry an egg on it, here is a Pentium that can run on a few milliwatts from a coin cell. Fortunately you won’t be running Windows 95 on it though.
We’re sure we’ll see plenty of projects here in the future using the Quark. Intel’s previous effort in this space, the Edison, has made several appearances. We’ve covered its launch in 2014, looked at someone running Doom on it, and examined its use with audio effects.
Thanks [Nolan M] for the tip.