دانلود کتاب آزمایشگاه اندازه گیری Arduino

The first considerations for a universal measuring system went in the direction of a digital PC oscilloscope combined with a signal generator. The In the first experiment I tested a Bluepill board with a STM32 controller. This Cortex M3 controller with a clock rate up to 72 MHz has a very fast AD converter and an integrated USB interface. Basically all tasks can be done by the same controller. Analog data is stored while at the same time values of a DDS table are sent to the fast PWM outputs to generate sine signals or other waveforms. The experiments went quite far, but in the end some interfering factors came to light. For the chosen tasks it is important that the measuring sample and the outputs run in a fast and very accurate time frame. Sampling rates up to 100 kHz at a PWM frequency of 125 kHz with two output and two input channels each were achieved. But there was a permanent slight flutter in the time frame, the cause of which was to be found in the simultaneous demands of the USB interface. If the actual measurement and signal output is executed in a timer interrupt with 100 kHz, no other interrupt should be allowed. As soon as a second timer interrupt or as in this case a USB interrupt is added, the absolutely uniform time grid is over. In addition, there were delivery problems. The general semiconductor crisis in 2021 meant that the Bluepill board was also hard to come by. That also ended this way. Bye bye Bluepill!