Mike R / Mbed 2 deprecated Pinscape_Controller

Important changes to repositories hosted on mbed.com

Mbed hosted mercurial repositories are deprecated and are due to be permanently deleted in July 2026.

To keep a copy of this software download the repository Zip archive or clone locally using Mercurial.

It is also possible to export all your personal repositories from the account settings page.

Dependencies:   USBDevice mbed FastAnalogIn FastIO FastPWM SimpleDMA

potSensor.h@44:b5ac89b9cd5d, 2016-02-07 (annotated)

Committer:
mjr
Date:
Sun Feb 07 03:07:11 2016 +0000
Revision:
44:b5ac89b9cd5d
Parent:
43:7a6364d82a41 
Work in progress on CCD speed-ups

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mjr 17:ab3cec0c8bf4 1 // Potentiometer plunger sensor
mjr 17:ab3cec0c8bf4 2 //
mjr 17:ab3cec0c8bf4 3 // This file implements our generic plunger sensor interface for a
mjr 43:7a6364d82a41 4 // potentiometer. The potentiometer resistance must be linear in
mjr 43:7a6364d82a41 5 // position. To connect physically, wire the fixed ends of the
mjr 43:7a6364d82a41 6 // potentiometer to +3.3V and GND (respectively), and connect the
mjr 43:7a6364d82a41 7 // wiper to an ADC-capable GPIO pin on the KL25Z. The wiper voltage
mjr 43:7a6364d82a41 8 // that we read on the ADC will vary linearly with the wiper position.
mjr 43:7a6364d82a41 9 // Mechanically attach the wiper to the plunger so that the wiper moves
mjr 43:7a6364d82a41 10 // in lock step with the plunger.
mjr 43:7a6364d82a41 11 //
mjr 43:7a6364d82a41 12 // Although this class is nominally for potentiometers, it will also
mjr 43:7a6364d82a41 13 // work with any other type of sensor that provides a single analog
mjr 43:7a6364d82a41 14 // voltage level that maps linearly to the position, such as an LVDT.
mjr 17:ab3cec0c8bf4 15
mjr 17:ab3cec0c8bf4 16
mjr 35:e959ffba78fd 17 class PlungerSensorPot: public PlungerSensor
mjr 17:ab3cec0c8bf4 18 {
mjr 17:ab3cec0c8bf4 19 public:
mjr 35:e959ffba78fd 20 PlungerSensorPot(PinName ao) : pot(ao)
mjr 17:ab3cec0c8bf4 21 {
mjr 17:ab3cec0c8bf4 22 }
mjr 17:ab3cec0c8bf4 23
mjr 35:e959ffba78fd 24 virtual void init()
mjr 17:ab3cec0c8bf4 25 {
mjr 17:ab3cec0c8bf4 26 }
mjr 17:ab3cec0c8bf4 27
mjr 44:b5ac89b9cd5d 28 virtual bool highResScan(float &pos)
mjr 17:ab3cec0c8bf4 29 {
mjr 23:14f8c5004cd0 30 // Take a few readings and use the average, to reduce the effect
mjr 23:14f8c5004cd0 31 // of analog voltage fluctuations. The voltage range on the ADC
mjr 23:14f8c5004cd0 32 // is 0-3.3V, and empirically it looks like we can expect random
mjr 23:14f8c5004cd0 33 // voltage fluctuations of up to 50 mV, which is about 1.5% of
mjr 23:14f8c5004cd0 34 // the overall range. We try to quantize at about the mm level
mjr 23:14f8c5004cd0 35 // (in terms of the plunger motion range), which is about 1%.
mjr 23:14f8c5004cd0 36 // So 1.5% noise is big enough to be visible in the joystick
mjr 23:14f8c5004cd0 37 // reports. Averaging several readings should help smooth out
mjr 23:14f8c5004cd0 38 // random noise in the readings.
mjr 44:b5ac89b9cd5d 39 //
mjr 44:b5ac89b9cd5d 40 // Readings through the standard AnalogIn class take about 30us
mjr 44:b5ac89b9cd5d 41 // each, so 5 readings is about 150us. This is plenty fast enough
mjr 44:b5ac89b9cd5d 42 // for even a low-res scan.
mjr 44:b5ac89b9cd5d 43 pos = (pot.read() + pot.read() + pot.read() + pot.read() + pot.read())/5.0;
mjr 17:ab3cec0c8bf4 44 return true;
mjr 17:ab3cec0c8bf4 45 }
mjr 17:ab3cec0c8bf4 46
mjr 44:b5ac89b9cd5d 47 virtual bool lowResScan(float &pos)
mjr 23:14f8c5004cd0 48 {
mjr 44:b5ac89b9cd5d 49 // Since we have only one analog input to sample, our read time is
mjr 44:b5ac89b9cd5d 50 // very fast compared to the image sensor alternatives, so there's no
mjr 44:b5ac89b9cd5d 51 // need to do anything different for a faster low-res scan. Simply
mjr 44:b5ac89b9cd5d 52 // take a normal high-res reading.
mjr 44:b5ac89b9cd5d 53 return highResScan(pos);
mjr 23:14f8c5004cd0 54 }
mjr 23:14f8c5004cd0 55
mjr 17:ab3cec0c8bf4 56 private:
mjr 23:14f8c5004cd0 57 AnalogIn pot;
mjr 17:ab3cec0c8bf4 58 };