148 lines
4.5 KiB
C++
148 lines
4.5 KiB
C++
/**
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* Class definition for MicroBitLightSensor.
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*
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* This is an object that interleaves light sensing with uBit.display.
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*/
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#include "MicroBit.h"
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/**
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* After the startSensing method has been called, this method will be called
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* MICROBIT_LIGHT_SENSOR_AN_SET_TIME after.
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*
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* It will then read from the currently selected channel using the AnalogIn
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* that was configured in the startSensing method.
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*/
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void MicroBitLightSensor::analogReady()
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{
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this->results[chan] = this->sensePin->read_u16();
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analogDisable();
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DigitalOut((PinName)(MICROBIT_DISPLAY_COLUMN_START + chan)).write(1);
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chan++;
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chan = chan % MICROBIT_LIGHT_SENSOR_CHAN_NUM;
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}
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/**
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* Forcibly disables the AnalogIn, otherwise it will remain in possession
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* of the GPIO channel it is using, meaning that the display will not be
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* able to use a channel (COL).
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*
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* This is required as per PAN 3, details of which can be found here:
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*
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* https://www.nordicsemi.com/eng/nordic/download_resource/24634/5/88440387
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*/
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void MicroBitLightSensor::analogDisable()
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{
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NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Disabled;
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NRF_ADC->CONFIG = (ADC_CONFIG_RES_8bit << ADC_CONFIG_RES_Pos) |
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(ADC_CONFIG_INPSEL_SupplyTwoThirdsPrescaling << ADC_CONFIG_INPSEL_Pos) |
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(ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos) |
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(ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos) |
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(ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos);
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}
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/**
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* The method that is invoked by sending MICROBIT_DISPLAY_EVT_LIGHT_SENSE
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* using the id MICROBIT_ID_DISPLAY.
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*
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* If you want to manually trigger this method, you should use the event bus.
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*
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* @note This is currently too churny, and allocates a lot of stuff on the stack
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* however, this makes this chunk of code platform agnostic in mbed land.
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*/
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void MicroBitLightSensor::startSensing(MicroBitEvent)
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{
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for(int rowCount = 0; rowCount < MICROBIT_DISPLAY_ROW_COUNT; rowCount++)
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DigitalOut((PinName)(MICROBIT_DISPLAY_ROW_START + rowCount)).write(0);
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PinName currentPin = (PinName)(MICROBIT_DISPLAY_COLUMN_START + chan);
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DigitalOut(currentPin).write(1);
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DigitalIn(currentPin, PullNone).~DigitalIn();
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if(this->sensePin != NULL)
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delete this->sensePin;
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this->sensePin = new AnalogIn(currentPin);
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analogTrigger.attach_us(this, &MicroBitLightSensor::analogReady, MICROBIT_LIGHT_SENSOR_AN_SET_TIME);
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}
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/**
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* Constructor.
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* Create a representation of the light sensor
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*/
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MicroBitLightSensor::MicroBitLightSensor() : analogTrigger()
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{
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this->chan = 0;
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uBit.MessageBus.listen(MICROBIT_ID_DISPLAY, MICROBIT_DISPLAY_EVT_LIGHT_SENSE, this, &MicroBitLightSensor::startSensing, MESSAGE_BUS_LISTENER_IMMEDIATE);
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this->sensePin = NULL;
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}
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/**
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* This method returns a summed average of the three sections of the display.
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*
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* A section is defined as:
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* ___________________
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* | 1 | | 2 | | 3 |
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* |___|___|___|___|___|
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* | | | | | |
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* |___|___|___|___|___|
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* | 2 | | 3 | | 1 |
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* |___|___|___|___|___|
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* | | | | | |
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* |___|___|___|___|___|
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* | 3 | | 1 | | 2 |
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* |___|___|___|___|___|
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*
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* Where each number represents a different section on the 5 x 5 matrix display.
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*
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* @return returns a value in the range 0 - 255 where 0 is dark, and 255
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* is very bright
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*
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* @note currently returns a value in the range 0 - 255 where 0 is dark, and 255
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* is very bright perhaps we should normalise the returned values into an SI unit!
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* TODO.
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*/
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int MicroBitLightSensor::read()
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{
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int sum = 0;
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for(int i = 0; i < MICROBIT_LIGHT_SENSOR_CHAN_NUM; i++)
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sum += results[i];
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int average = sum / MICROBIT_LIGHT_SENSOR_CHAN_NUM;
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average = min(average, MICROBIT_LIGHT_SENSOR_MAX_VALUE);
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average = max(average, MICROBIT_LIGHT_SENSOR_MIN_VALUE);
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int inverted = (MICROBIT_LIGHT_SENSOR_MAX_VALUE - average) + MICROBIT_LIGHT_SENSOR_MIN_VALUE;
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int a = 0;
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int b = 255;
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int normalised = a + ((((inverted - MICROBIT_LIGHT_SENSOR_MIN_VALUE)) * (b - a))/ (MICROBIT_LIGHT_SENSOR_MAX_VALUE - MICROBIT_LIGHT_SENSOR_MIN_VALUE));
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return normalised;
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}
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/**
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* The destructor restores the default Display Mode and tick speed, and also
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* removes the listener from the MessageBus.
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*/
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MicroBitLightSensor::~MicroBitLightSensor()
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{
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uBit.MessageBus.ignore(MICROBIT_ID_DISPLAY, MICROBIT_DISPLAY_EVT_LIGHT_SENSE, this, &MicroBitLightSensor::startSensing);
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}
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