Hi,

   I'm new to the hobby (of drones, not R/C Aircraft).  I love computers and programming, so I thought I'd take on an educational project of making an autopilot out of a $35 Raspberry Pi computer. So far I have a functioning Mini Maestro servo controller and an MPXV7002DP airspeed sensor that the Mini Maestro can sample with an analog input. My next hurdle is RPM.  I purchased a Hall Effect sensor with magnets that is meant for a telemetry module.  However, my goal is to avoid using the Pi's processor time to calculate RPM from the GPIO pins. What I'd like to have is a circuit that counts pulses off the hall effect sensor, and at set intervals, calculates the RPM, stores it in a register and then resets itself for the next sample, etc....  The best way to access this would be over I2C interface, so it could be sampled on demand.  Does anyone know of an existing breakout board or chip that does this?  I'm planning on using a 4 cycle glow powered aircraft for this project, and hence the need for such a device.  The absolute highest required RPM range would be somewhere in the ballpark of 10,000 RPM.  I found a PC fan controller by analog devices (ADT7470) that does this for 4 PC fans It even has temperature inputs for setting limits but I believe the RPM is limited to lower than what I require. If anyone knows of such an IC or board, please let me know!  I also found an AD650 chip from Analog Devices that converts the pulses to a varying voltage which could then be sampled on the Mini Maestro; but I'm looking for a ready made solution since building circuit boards isn't my strong suit.  Any Ideas??

Jim

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