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...