For a customer, I need to know the Rotations Per Minute of an industrial fan motor. It has a tachometer pin that you pull up to VCC and it’ll pull down upon the fan rotating to provide a nice pulse train.
I’ve formerly solved problems like this by using interrupts on the Microcontroller, but I’m afraid that doing so will cause problems to other timing critical parts of the system. What I would love to find is a chip that can just sit there and count and when it suits my main program, I can poll it to know how many counts it has received since last polling. The most suited part I have found is the NCT80 from OnSemi ($3.8). This uses I2C, so I won’t need to use any additional pins from my MCU so it’s not a bad solution.
But - shouldn’t there be more suppliers of IC’s like this? Or does just everyone else just throw a dedicated Microcontroller at this problem? How would you solve this if you cannot use the main Microcontroller? How would you go about making a Tachometer like this?