Program Listing for File MicroBitCompassCalibrator.cpp#
↰ Return to documentation for file (libraries/codal-microbit-v2/source/MicroBitCompassCalibrator.cpp)
/*
The MIT License (MIT)
Copyright (c) 2016 British Broadcasting Corporation.
This software is provided by Lancaster University by arrangement with the BBC.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
*/
#include "MicroBitConfig.h"
#include "MicroBitCompassCalibrator.h"
#include "EventModel.h"
using namespace codal;
#define CALIBRATION_INCREMENT 200
MicroBitCompassCalibrator::MicroBitCompassCalibrator(Compass& _compass, Accelerometer& _accelerometer, MicroBitDisplay& _display) : compass(_compass), accelerometer(_accelerometer), display(_display)
{
this->storage = NULL;
if (EventModel::defaultEventBus)
EventModel::defaultEventBus->listen(MICROBIT_ID_COMPASS, MICROBIT_COMPASS_EVT_CALIBRATE, this, &MicroBitCompassCalibrator::calibrateUX, MESSAGE_BUS_LISTENER_IMMEDIATE);
}
MicroBitCompassCalibrator::MicroBitCompassCalibrator(Compass& _compass, Accelerometer& _accelerometer, MicroBitDisplay& _display, MicroBitStorage &storage) : compass(_compass), accelerometer(_accelerometer), display(_display)
{
this->storage = &storage;
//Attempt to load any stored calibration datafor the compass.
KeyValuePair *calibrationData = this->storage->get("compassCal");
if(calibrationData != NULL)
{
CompassCalibration cal;
memcpy(&cal, calibrationData->value, sizeof(CompassCalibration));
compass.setCalibration(cal);
delete calibrationData;
}
if (EventModel::defaultEventBus)
EventModel::defaultEventBus->listen(MICROBIT_ID_COMPASS, MICROBIT_COMPASS_EVT_CALIBRATE, this, &MicroBitCompassCalibrator::calibrateUX, MESSAGE_BUS_LISTENER_IMMEDIATE);
}
float MicroBitCompassCalibrator::measureScore(Sample3D &c, Sample3D *data, int samples)
{
float minD;
float maxD;
minD = maxD = c.dSquared(data[0]);
for (int i = 1; i < samples; i++)
{
float d = c.dSquared(data[i]);
if (d < minD)
minD = d;
if (d > maxD)
maxD = d;
}
return (maxD - minD);
}
CompassCalibration MicroBitCompassCalibrator::calibrate(Sample3D *data, int samples)
{
Sample3D centre = approximateCentre(data, samples);
return spherify(centre, data, samples);
}
CompassCalibration MicroBitCompassCalibrator::spherify(Sample3D centre, Sample3D *data, int samples)
{
// First, determine the radius of the enclosing sphere from the given centre.
// n.b. this will likely be different to the radius from the centre of mass previously calculated.
// We use the same algorithm though.
CompassCalibration result;
float radius = 0;
float scaleX = 0.0;
float scaleY = 0.0;
float scaleZ = 0.0;
float scale = 0.0;
float weightX = 0.0;
float weightY = 0.0;
float weightZ = 0.0;
for (int i = 0; i < samples; i++)
{
int d = sqrt((float)centre.dSquared(data[i]));
if (d > radius)
radius = d;
}
// Now, for each data point, determine a scalar multiplier for the vector between the centre and that point that
// takes the point onto the surface of the enclosing sphere.
for (int i = 0; i < samples; i++)
{
// Calculate the distance from this point to the centre of the sphere
float d = sqrt(centre.dSquared(data[i]));
// Now determine a scalar multiplier that, when applied to the vector to the centre,
// will place this point on the surface of the sphere.
float s = (radius / d) - 1;
if (scale < s)
scale = s;
// next, determine the scale effect this has on each of our components.
float dx = (data[i].x - centre.x);
float dy = (data[i].y - centre.y);
float dz = (data[i].z - centre.z);
weightX += s * fabsf(dx / d);
weightY += s * fabsf(dy / d);
weightZ += s * fabsf(dz / d);
}
float wmag = sqrt((weightX * weightX) + (weightY * weightY) + (weightZ * weightZ));
scaleX = 1.0 + scale * (weightX / wmag);
scaleY = 1.0 + scale * (weightY / wmag);
scaleZ = 1.0 + scale * (weightZ / wmag);
result.scale.x = (int)(1024 * scaleX);
result.scale.y = (int)(1024 * scaleY);
result.scale.z = (int)(1024 * scaleZ);
result.centre.x = centre.x;
result.centre.y = centre.y;
result.centre.z = centre.z;
result.radius = radius;
return result;
}
/*
* Performs an interative approximation (hill descent) algorithm to determine an
* estimated centre point of a sphere upon which the given data points reside.
*
* @param data an array containing sample points
* @param samples the number of sample points in the 'data' array.
*
* @return the approximated centre point of the points in the 'data' array.
*/
Sample3D MicroBitCompassCalibrator::approximateCentre(Sample3D *data, int samples)
{
Sample3D c,t;
Sample3D centre = { 0,0,0 };
Sample3D best = { 0,0,0 };
float score;
for (int i = 0; i < samples; i++)
{
centre.x += data[i].x;
centre.y += data[i].y;
centre.z += data[i].z;
}
// Calclulate a centre of mass for our input samples. We only use this for validation purposes.
centre.x = centre.x / samples;
centre.y = centre.y / samples;
centre.z = centre.z / samples;
// Start hill climb in the centre of mass.
c = centre;
// calculate the nearest and furthest point to us.
score = measureScore(c, data, samples);
// iteratively attempt to improve position...
while (1)
{
for (int x = -CALIBRATION_INCREMENT; x <= CALIBRATION_INCREMENT; x=x+CALIBRATION_INCREMENT)
{
for (int y = -CALIBRATION_INCREMENT; y <= CALIBRATION_INCREMENT; y=y+CALIBRATION_INCREMENT)
{
for (int z = -CALIBRATION_INCREMENT; z <= CALIBRATION_INCREMENT; z=z+CALIBRATION_INCREMENT)
{
t = c;
t.x += x;
t.y += y;
t.z += z;
float s = measureScore(t, data, samples);
if (s < score)
{
score = s;
best = t;
}
}
}
}
if (best.x == c.x && best.y == c.y && best.z == c.z)
break;
c = best;
}
return c;
}
void MicroBitCompassCalibrator::calibrateUX(MicroBitEvent)
{
struct Point
{
uint8_t x;
uint8_t y;
};
const int PERIMETER_POINTS = 25;
const int PIXEL1_THRESHOLD = 200;
const int PIXEL2_THRESHOLD = 680;
const int REDISPLAY_MSG_TIMEOUT_MS = 30000;
const int SAMPLES_END_MSG_COUNT = 15;
const int TIME_STEP = 100;
const int MSG_TIME = 155 * TIME_STEP; //We require MSG_TIME % TIME_STEP == 0
target_wait(100);
static const Point perimeter[PERIMETER_POINTS] = {{0,0}, {1,0}, {2,0}, {3,0}, {4,0}, {0,1}, {1,1}, {2,1}, {3,1}, {4,1}, {0,2}, {1,2}, {2,2}, {3,2}, {4,2}, {0,3}, {1,3}, {2,3}, {3,3}, {4,3}, {0,4}, {1,4}, {2,4}, {3,4}, {4,4}};
Point cursor = {2,2};
MicroBitImage img(5,5);
MicroBitImage smiley("0,255,0,255,0\n0,255,0,255,0\n0,0,0,0,0\n255,0,0,0,255\n0,255,255,255,0\n");
Sample3D data[PERIMETER_POINTS];
uint8_t visited[PERIMETER_POINTS] = { 0 };
uint8_t cursor_on = 0;
uint8_t samples = 0;
uint8_t samples_this_period = 0;
int16_t remaining_scroll_time = MSG_TIME; // 32s maximum in uint16_t
// Set the display to full brightness (in case a user program has it very dim / off). Store the current brightness, so we can restore it later.
int displayBrightness = display.getBrightness();
display.setBrightness(255);
// Firstly, we need to take over the display. Ensure all active animations are paused.
display.stopAnimation();
while(samples < PERIMETER_POINTS)
{
// Scroll a message the first time we enter this loop and every REDISPLAY_MSG_TIMEOUT_MS
if (remaining_scroll_time == MSG_TIME || remaining_scroll_time <= -REDISPLAY_MSG_TIMEOUT_MS) {
display.clear();
display.scrollAsync("TILT TO FILL SCREEN "); // Takes about 14s
remaining_scroll_time = MSG_TIME;
samples_this_period = 0;
}
else if (remaining_scroll_time == 0 || samples_this_period == SAMPLES_END_MSG_COUNT)
{
// This stops the scrolling at the end of the message.
// ...and it is the source of the ((MSG_TIME % TIME_STEP) == 0) requirement
display.stopAnimation();
}
// update our model of the flash status of the user controlled pixel.
cursor_on = (cursor_on + 40) % 200;
// take a snapshot of the current accelerometer data.
int x = accelerometer.getX();
int y = accelerometer.getY();
// Deterine the position of the user controlled pixel on the screen.
if (x < -PIXEL2_THRESHOLD)
cursor.x = 0;
else if (x < -PIXEL1_THRESHOLD)
cursor.x = 1;
else if (x > PIXEL2_THRESHOLD)
cursor.x = 4;
else if (x > PIXEL1_THRESHOLD)
cursor.x = 3;
else
cursor.x = 2;
if (y < -PIXEL2_THRESHOLD)
cursor.y = 0;
else if (y < -PIXEL1_THRESHOLD)
cursor.y = 1;
else if (y > PIXEL2_THRESHOLD)
cursor.y = 4;
else if (y > PIXEL1_THRESHOLD)
cursor.y = 3;
else
cursor.y = 2;
img.clear();
// Turn on any pixels that have been visited.
for (int i=0; i<PERIMETER_POINTS; i++)
if (visited[i] == 1)
img.setPixelValue(perimeter[i].x, perimeter[i].y, 255);
// Update the pixel at the users position.
img.setPixelValue(cursor.x, cursor.y, cursor_on);
// Update the buffer to the screen ONLY if we've finished scrolling the message
if (remaining_scroll_time < 0 || samples_this_period > SAMPLES_END_MSG_COUNT)
display.image.paste(img,0,0,0);
// test if we need to update the state at the users position.
for (int i=0; i<PERIMETER_POINTS; i++)
{
if (cursor.x == perimeter[i].x && cursor.y == perimeter[i].y && !(visited[i] == 1))
{
// Record the sample data for later processing...
data[samples] = compass.getSample(RAW);
// Record that this pixel has been visited.
visited[i] = 1;
samples++;
samples_this_period++;
}
}
target_wait(TIME_STEP);
remaining_scroll_time-=TIME_STEP;
}
CompassCalibration cal = calibrate(data, samples);
compass.setCalibration(cal);
if(this->storage)
this->storage->put("compassCal", (uint8_t *) &cal, sizeof(CompassCalibration));
// Show a smiley to indicate that we're done, and continue on with the user program.
display.clear();
display.printAsync(smiley, 0, 0, 0, 1500);
target_wait(1000);
display.clear();
// Retore the display brightness to the level it was at before this function was called.
display.setBrightness(displayBrightness);
}