Chris M.

Concept External test equipment is a powerful but often overlooked tool for debugging particular kinds of software problems. In particular, test equipment like oscilloscopes and logic analyzers are well suited to investigating timing related issues on embedded systems. Why is test equipment suited to helping with issues related to timing? Oscilloscopes and logic analyzers can easily provide microsecond or better measurements and, unlike software based monitoring approaches, they aren't affected by other software running on the system. Embedded systems are ideal for this approach as they both provide the io outputs required for timing measurement, and often lack the advanced debugging facilities found in desktop/laptop processors and operating systems that would make this approach less necessary. At the conclusion of  debugging some 1-Wire bus contention issues  I was still seeing CRC errors reported periodically. Here is how I used an oscilloscope to track down the lik...

Background I've been playing around with the Maxim  DS18B20 digital temperature sensor. These are neat devices that provide a digital temperature, which means they provide an actual Celsius reading in digital form, with a pretty high level of accuracy, +/- 0.5C from -10C to 85C. They are also quite compact. Here is the typical TO92-3 form factor that the DS18B20 comes in. Why not a thermistor connected to an ADC? Your microprocessor may not have an accurate enough or linear enough ADC to let you attain the desired temperature accuracy. In my case I'm using the Espressif ESP32 . The ESP32 is a great processor but its ADC still needs some work . Code to linearize the ADC results was added earlier this year but the biggest missing piece is proper calibration of the ADCs vref. Without this the scaling of ADC values can vary by several percent. Good news is that factory calibration is possible and should be coming. Thermistors also have a non-linear resist...

We have a stack of lumber, copper pipe, and trim that has been on the basement floor in our last house and that we moved over to our new house. It's tough to keep the material organized, the pipes, trim and lumber is stacked together and tough to get at. It's not an effective use of floor space and the lumber and pipes are quite long, some of the pieces are 10' long. If I built a 10' long workbench I could store the material below it, either on the floor or shelves, and it would provide space to work on projects and storage space for a chop saw and other tools. I've used Tinkercad to make some 3D mockups for work projects before and it worked pretty well. Tinkercad can be used to create designs for 3D printing but in this case I used it to visualize the workbench and determine how to construct it. 3D model Here is the 3D design that you can view, duplicate, and edit. The dimensions of the lumber in the model should be correct. Note that the scale is...

Tesla owners have noticed a change in the behavior of their cars, specifically in the performance models such as the P85 and the P90DL, where the performance of the cars doesn't seem to match previous or listed results. User wk057 has done some pretty extensive reverse engineering, modifications, and looking into the internal systems of the car, including the battery pack. On TeslaMotorsClub what started as a thread about battery pack capacities not matching advertized amounts, rated amount of available energy doesn't even match the car's own reported energy , turned into a thread called Pack Performance and Launch Mode Limits . This thread has kicked off a bit of a firestorm as these performance limits weren't documented or disclosed. It appears pretty clear that Tesla is counting the number of Launches (done through launch mode), as well as the number of Wide Open Throttle (WoT) events. When those counts go beyond some predefined values the car will reduce the am...

I attended CES 2017 in Las Vegas. Booking the trip late I ended up on Spirit airlines. It was both non-stop, making it six hours to Las Vegas from Boston, and affordable, less than $300 for a one way trip compared to around $700 with JetBlue. Here are some tips that might help you when travelling on Spirit from Boston Logan airport. Eat Spirit is located in the B-terminal, gates B-37 and 38, with its own TSA security checkpoint. While it does have restrooms and places to sit the food selection is limited to a single food stand. I'd recommend eating at the Legal C Bar (number 77 in the image below) prior to going through the terminal security checkpoint. The food and service there were great. Drink The water and other drinks are cheaper if you buy them at the food cart rather than on the flight. Seats The seats on Spirit don't recline. They do this to reduce weight, seat cost, seat maintenance costs, and so seats don't impact the free space of other passengers,...

Faraday Future (FF) unveiled their FF91 electric car at CES 2017 in Las Vegas this past week. Some of the highlights from their presentation: 2.39s 0 - 60 mph, faster than the Tesla Model S P100D 130 kW battery (Tesla's largest is 100 kWh) Autonomous driving. And they demoed parking in this video: Here is their booth on the floor of the show: There were quite a few FF employees attending the show. Normal attendees were kept away from the car but some people were let inside of the area and able to get up close and take a look at it. My take on Faraday future I'm an engineer and an owner of a Tesla Model S. I'm also an investor in Tesla. I'm not skeptical of FF because they are competing with Tesla or claim to be building a better car. There is plenty of room in the EV market for well built vehicles. Due to the growth in the EV market FF could sell tens of thousands of vehicles per year without much impact on Tesla's sales. I'm a fan of E...