Posts Tagged “oscilloscope”
A recent PetitFoo talk at the Chaospott on how to debounce keys with a Schmitt trigger prompted me to play with a 74HC14 IC I had lying around.
A Schmitt-trigger converts an analog voltage to a digital logic level. It has two voltage thresholds, and the interesting thing happens between the two:
- Below the lower threshold the input is considered logically low, so the inverter outputs a logic high.
- Above the upper threshold the input is considered logically high, so the inverter outputs a logic low.
- Between the two thresholds the Schmitt-trigger keeps the input state, so the output doesn't change.
Here is an oscilloscope screenshot of the basic behavior of one inverter of the 74HC14, using a triangle wave from the function generator as the input: More ...
The LPC804 is a new low-end microcontroller from NXP in the LPC8xx range. The LPC804 is interesting, because so far it is the only LPC microcontroller which contains a Programmable Logic Unit (PLU), a miniature FPGA with 26 5-input lookup tables and 4 bits of state. Unfortunately NXP doesn't publish the timing parameters of this circuitry. You are supposed to use NXPs proprietary PLU configuration tool, which is available only for Microsoft Windows.
Here is a quick measurement of the speed of the LUTs in the PLU: More ...