work in progress
Dependencies: FastAnalogIn FastIO USBDevice mbed FastPWM SimpleDMA
Fork of Pinscape_Controller by
potSensor.h@23:14f8c5004cd0, 2015-06-03 (annotated)
- Committer:
- mjr
- Date:
- Wed Jun 03 18:50:34 2015 +0000
- Revision:
- 23:14f8c5004cd0
- Parent:
- 17:ab3cec0c8bf4
Use regular AnalogIn (not FastAnalogIn) for potentiometer readings, and take the average of several readings, to reduce noise; add a minimum distance threshold before a firing event when crossing the rest position.
Who changed what in which revision?
User | Revision | Line number | New 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 | 17:ab3cec0c8bf4 | 4 | // potentiometer. |
mjr | 17:ab3cec0c8bf4 | 5 | |
mjr | 17:ab3cec0c8bf4 | 6 | #include "FastAnalogIn.h" |
mjr | 17:ab3cec0c8bf4 | 7 | |
mjr | 17:ab3cec0c8bf4 | 8 | // The potentiometer doesn't have pixels, but we still need an |
mjr | 17:ab3cec0c8bf4 | 9 | // integer range for normalizing our digitized voltage level values. |
mjr | 17:ab3cec0c8bf4 | 10 | // The number here is fairly arbitrary; the higher it is, the finer |
mjr | 17:ab3cec0c8bf4 | 11 | // the digitized steps. A 40" 1080p HDTV has about 55 pixels per inch |
mjr | 17:ab3cec0c8bf4 | 12 | // on its physical display, so if the on-screen plunger is displayed |
mjr | 17:ab3cec0c8bf4 | 13 | // at roughly the true physical size, it's about 3" on screen or about |
mjr | 17:ab3cec0c8bf4 | 14 | // 165 pixels. So the minimum quantization size here should be about |
mjr | 17:ab3cec0c8bf4 | 15 | // the same. For the pot sensor, this is just a scaling factor, |
mjr | 17:ab3cec0c8bf4 | 16 | // so higher values don't cost us anything (unlike the CCD, where the |
mjr | 17:ab3cec0c8bf4 | 17 | // read time is proportional to the number of pixels we sample). |
mjr | 17:ab3cec0c8bf4 | 18 | const int npix = 4096; |
mjr | 17:ab3cec0c8bf4 | 19 | |
mjr | 17:ab3cec0c8bf4 | 20 | class PlungerSensor |
mjr | 17:ab3cec0c8bf4 | 21 | { |
mjr | 17:ab3cec0c8bf4 | 22 | public: |
mjr | 17:ab3cec0c8bf4 | 23 | PlungerSensor() : pot(POT_PIN) |
mjr | 17:ab3cec0c8bf4 | 24 | { |
mjr | 17:ab3cec0c8bf4 | 25 | } |
mjr | 17:ab3cec0c8bf4 | 26 | |
mjr | 17:ab3cec0c8bf4 | 27 | void init() |
mjr | 17:ab3cec0c8bf4 | 28 | { |
mjr | 17:ab3cec0c8bf4 | 29 | } |
mjr | 17:ab3cec0c8bf4 | 30 | |
mjr | 17:ab3cec0c8bf4 | 31 | bool highResScan(int &pos) |
mjr | 17:ab3cec0c8bf4 | 32 | { |
mjr | 23:14f8c5004cd0 | 33 | // Take a few readings and use the average, to reduce the effect |
mjr | 23:14f8c5004cd0 | 34 | // of analog voltage fluctuations. The voltage range on the ADC |
mjr | 23:14f8c5004cd0 | 35 | // is 0-3.3V, and empirically it looks like we can expect random |
mjr | 23:14f8c5004cd0 | 36 | // voltage fluctuations of up to 50 mV, which is about 1.5% of |
mjr | 23:14f8c5004cd0 | 37 | // the overall range. We try to quantize at about the mm level |
mjr | 23:14f8c5004cd0 | 38 | // (in terms of the plunger motion range), which is about 1%. |
mjr | 23:14f8c5004cd0 | 39 | // So 1.5% noise is big enough to be visible in the joystick |
mjr | 23:14f8c5004cd0 | 40 | // reports. Averaging several readings should help smooth out |
mjr | 23:14f8c5004cd0 | 41 | // random noise in the readings. |
mjr | 23:14f8c5004cd0 | 42 | pos = int((pot.read() + pot.read() + pot.read())/3.0 * npix); |
mjr | 17:ab3cec0c8bf4 | 43 | return true; |
mjr | 17:ab3cec0c8bf4 | 44 | } |
mjr | 17:ab3cec0c8bf4 | 45 | |
mjr | 23:14f8c5004cd0 | 46 | int lowResScan() |
mjr | 23:14f8c5004cd0 | 47 | { |
mjr | 23:14f8c5004cd0 | 48 | // Use an average of several readings. Note that even though this |
mjr | 23:14f8c5004cd0 | 49 | // is nominally a "low res" scan, we can still afford to take an |
mjr | 23:14f8c5004cd0 | 50 | // average. The point of the low res interface is speed, and since |
mjr | 23:14f8c5004cd0 | 51 | // we only have one analog value to read, we can afford to take |
mjr | 23:14f8c5004cd0 | 52 | // several samples here even in the low res case. |
mjr | 23:14f8c5004cd0 | 53 | return int((pot.read() + pot.read() + pot.read())/3.0 * npix); |
mjr | 23:14f8c5004cd0 | 54 | } |
mjr | 23:14f8c5004cd0 | 55 | |
mjr | 17:ab3cec0c8bf4 | 56 | void sendExposureReport(USBJoystick &) |
mjr | 17:ab3cec0c8bf4 | 57 | { |
mjr | 17:ab3cec0c8bf4 | 58 | } |
mjr | 17:ab3cec0c8bf4 | 59 | |
mjr | 17:ab3cec0c8bf4 | 60 | private: |
mjr | 23:14f8c5004cd0 | 61 | AnalogIn pot; |
mjr | 17:ab3cec0c8bf4 | 62 | }; |