Open Protocol

From Aeroscope's beginning, we set out to design a completely open protocol. We wanted to empower users to write their own apps because we knew we could never envision all the unique applications people would use Aeroscope for. 

Today, we have released complete documentation on Aeroscope's Bluetooth LE communication protocol. This datasheet is our initial release. It will evolve as we get feedback and questions. We have been beta-testing this documentation with a college student who has been using it to write an Aeroscope app for his senior project. Let us know how you use it.

We are also committed to open-sourcing our app. Right now, we are preparing our app for submission to Apple's app store. In the coming days (before we ship), we will be releasing the source code on Github as well. Our app is written in Swift and should serve as a good starting point for any custom apps you write or any source code contributions you want to make.


Aeroscope Multiplatform Support

The most common question we get is whether we plan to support multiple platforms. Right now, I can say with 100% certainty that we will.

Our main strategy by launching with only iOS support was to ensure a good user experience on one platform rather than a crummy experience on multiple platforms. Due to hardware and software variations between different phone and tablet vendors, it is much harder to ensure fast Bluetooth LE transmission on Android vs iOS. The app might work really well on one phone model but not at all on another without additional testing and modification. This made our launch platform decision very clear: iOS

Our iOS app is fully native, written in Apple's new language: Swift. We chose to write a native app first to ensure a high-quality user experience in the minimal amount of time. Our next platform priorities are Windows and Android. To achieve this, we are going to create a second app using a cross-platform toolkit. Over time, we will additionally add support for Linux and MacOS as we add polish for those platforms. 

If you are one of those people waiting for us to branch out from iOS: Don't worry, we'll get there. We plan to release an initial cross-platform app by Sept. 2017, with beta versions available before then.

If you can't wait that long, there has never been a better time to buy an iPad. Apple just dropped their prices and you can buy a full-sized iPad for $329.  The iPad mini 2 is going for around $250 on amazon


Aeroscope Live on Crowdsupply

We are excited to announce that Aeroscope 100 is now for sale on Crowd Supply. All of our parts are finished and have been delivered to our facility. Manufacturing has started and we will ship our first batch of units on April 20th. Get yours today!


Progress Update

It has been a while since we have posted an update and we've been getting some questions regarding the future of Aeroscope. Here is a short update about what we've been working on for the last few months.

We have been working hard here at Aeroscope Labs ramping up for our upcoming product launch. The lower cost Aeroscope 100 hardware design is just about finalized and we are putting the final touches on the iOS app. Production quantities of parts are starting to show up at our Boulder office and we are ironing out the kinks with our production test process. The excitement is building as we get closer and closer to launch day!

We are planning on running another campaign on Crowd Supply in late January. This will be more of a pre-sale campaign than a traditional crowdfunding campaign. We are building up an inventory of Aeroscope 100s that will be ready to ship prior to the campaign's launch. This means that Aeroscope will be shipped out to our backers as soon as they place their order. The campaign won't have a funding goal, ensuring that anyone who orders an Aeroscope will receive one. If we sell out of our existing inventory there will be a 6 week delay while we build up more Aeroscopes.

After all of the Crowd Supply backers have received their Aeroscopes we will be selling through our website. We also intend on selling through a few distributors but don't have a firm timeline on when that will begin.

We appreciate all of the words of support and encouragement we have received surrounding Aeroscope. We can't wait to get this great product out into the world!


Pre-sale Campaign

We are excited to announce more details regarding our upcoming crowd funding campaign. We have decided to host our campaign on Crowd Supply.  Crowd Supply is a hardware only funding platform that focuses on bringing well prepared, mature products to market. They perform a thorough vetting process before agreeing to represent projects and they have a 100% delivery rate on their funded projects.

This focus on quality products and user satisfaction resonates with Jon and myself. Although we have been working on Aeroscope for two years, we have waited to launch this campaign until now. Not only did we want to ensure that we had a solid design but also that we had anticipated all costs, schedule impacts, manufacturing time frames, and regulatory hurdles. This careful planning and hard work will ensure that Aeroscope is a quality product and will be delivered to its backers on time. Our campaign will launch at 9am EDT on Tuesday June 14. Click here to visit our campaign page.


Manufacturing Aeroscope

As we have mentioned in previous posts, we have identified a US based manufacturing partner to produce Aeroscope. This Wisconsin based company has three production facilities and has been working in the electronics industry for over 35 years. We recently traveled to Wisconsin and toured a few of their plants. We were impressed with their capabilities and are excited for them to start cranking out Aeroscopes!

We are often asked why we have decided to produce Aeroscope in the USA and not in China. Jonathan and I have experience manufacturing products in the USA, Mexico, Malaysia, and China. We have both felt the pros and cons of off shore manufacturing first hand.

Overseas manufacturing makes sense for very high volume products but not necessarily for low or medium volume production. Costs in China are rising [1] and producing products in Asia isn't as compelling as it once was [2]. Long and expensive flights, dramatic time zone differences, language barriers, and long over ocean shipping times all detract from the attractiveness of Asian manufacturing. I have been involved in multiple product launches that experienced weeks of schedule slip due to back and forth email correspondence with Asian manufacturing partners.

Additionally, there is a lack of control when production volumes aren't large enough to warrant your own dedicated production line. Large factories will agree to manufacture your product but will try and squeeze the manufacturing in during down times between their larger volume clients. This means that you don't know exactly when the build will take place and you won't be there to support any problems that may arise. 

For these reasons, we have decided to produce Aeroscope at US based manufacturing facilities. 


Measuring Probe Capacitance


An important but often overlooked oscilloscope characteristic is probe input impedance. An ideal oscilloscope would have an infinitely large input impedance so that the circuit being measured would be completely unaffected by the presence of the probe. Unfortunately, real oscilloscopes don't have an infinitely high input impedance. It is important to understand how the probe can affect signals being measured so you can be certain that the probe isn't causing measurement errors.

Probe input impedance is modeled as the parallel combination of a resistance and capacitance. Most oscilloscopes have a probe input resistance of either 1M or 10M ohms, and an input capacitance from less than a pico Farad (active FET probes) all the way up to 100 pF (low bandwidth passive probes). The resistive component is generally of little concern if the source impedance of the signal being measured is less than 10K (this would be a 1% error if using a probe with a 1M input resistance). However, the capacitive component can present low impedances to the circuit being measured, especially at frequencies greater than a few MHz. For example, a probe with a 20pF input capacitance will present an impedance of 400 ohms at 20 MHz or 80 ohms at 100 MHz. This is obviously much less than the resistive impedance and could attenuate the signal being measured. See Figure 1 below for a typical test setup. If Rsource is 100 ohms and Cprobe is 20 pF the source resistance and probe impedance will act as a low pass filter with a corner frequency of 80 MHz. This means that even if you are using a high bandwidth oscilloscope, the probe itself could limit your bandwidth and mask any high frequency behavior that you are trying to measure.

Figure 1. Typical Test Setup

Figure 1. Typical Test Setup

From the above explanation, it is clear that having an understanding of input capacitance is important when measuring high frequency signals. The next few sections will explain how one can measure this probe capacitance. We will measure the input capacitance of Aeroscope as a demonstration of this procedure.

One way to calculate the capacitance of an unknown load is to apply a step function and measure the rise time. The time constant Tau is equal to the product of the resistive and capacitive impedance elements. Tau is the time required for the voltage to rise from its initial value to 63% of its final value. Figure 1 above will be used to represent the test setup, Rload is not present and Tau is equal to (Rsource || Rprobe) * Cprobe. Use a value of Rsource that is large enough so that each pF of capacitance causes an observable delay in rise time. The value of Rsource we used for this test is 470k ohm. This gives a Tau of 0.45 us per pF, which is easily observable on an oscilloscope.

Once the test is setup, adjust the amplitude of the square wave source until the signal occupies the entire screen, see Figure 2 below. Since the scope screen is 8 divisions tall and we are looking for the point that the signal has risen by 63% we need to see how long it takes the signal to rise 5 divisions (5/8 = 62.5%).

Figure 2. Step response with amplitude equal to the full oscilloscope screen. Time scale = 5 us/division

Figure 2. Step response with amplitude equal to the full oscilloscope screen. Time scale = 5 us/division

The rise time is measured as shown in Figure 3 to be roughly 4.5 us.  The source resistor (470k) in parallel with the scope's input resistance (10M) gives an effective source resistance (Rse) of 449K (Rprobe || Rsource). The input capacitance can then be calculated to be (Tau/Rse) equal to 10 pF. This capacitive load is comparable or lower than most passive probes that come standard with 100 MHz bandwidth oscilloscopes.

Figure 3. Rise time measurement. Time scale = 1us/division

Figure 3. Rise time measurement. Time scale = 1us/division

A 10 pF input capacitance will present an impedance of 159 ohms at 100 MHz. This would cause .4 dB of attenuation with Rs of 50 ohms, or 1.5 dB of attenuation with Rs of 100 ohms.


New Tip Design


We finally got our first machined prototype probe tips back from our supplier last week. We decided to go with a company that specializes in RF connectors. If they can make connectors precise enough to handle multiple GHz, they should be good enough for our application. 

Our original tip was hand-made with parts from an SMA cable kit. We used a square .1 inch header pin for the tip and used an SMA crimp sleeve soldered to a male SMA connector as the body. 

While crude, these first prototypes helped us prove out our design and validated our decision to use an SMA connector on the body of the oscilloscope. However, we knew hand soldering thousands of tips was out of the question. We had to design a tip that had fewest parts possible and was easy to assemble to keep costs down. Ideally, the parts would be press fit to keep assembly costs down. Enter our new design...

We got the tip down to three parts that are all press-fit together. The probe tip is gold-plated phosphor bronze for strength and durability. The body is a nickel-plated brass alloy with straight knurling on the connector side. We didn't want to use a hex-style body like on our first prototype because we were afraid people might use a wrench to tighten. While most RF connectors have hex bodies, they are only meant to enable tightening to a precise torque specification for precision measurements. We chose a straight knurl body to enable finger tightening and prevent someone from wailing on it with a wrench. The lining between the probe tip and body is PTFE. This is a common dielectric for RF connector applications and is easy for suppliers to source.