lockin.h

00001 #ifndef MBED_LOCKIN_H
00002 #define MBED_LOCKIN_H
00003 
00004 #include "mbed.h"
00005 #include "adc.h"
00006 
00007 #define MBEDFREQUENCY 96000 //frequency of the mBed in KHz
00008 
00009 //#define I_Volts_SAT 5 // this is 5V (the saturation voltage for the APD+LockIn+ADC, being it the arduino (when in normal mode) or the SPI. This saturation voltage could be different for each mode!?
00010 
00011 #define LOCKIN_ADC_PIN      p18 //ADC pin : connect to lockin "output"
00012 
00013 #define LOCKIN_REF_PIN      p23 //PWM pin : connect to lockin reference signal.
00014 #define LOCKIN_LASER_PIN    p25 //PWM pin : connect to laser control - note: the red laser by default, but could be a fourth IR laser...
00015 // p21 to p26 are used by the PWM timers even if only 2 pin are connected to the circuit
00016 
00017 #define BUFFER_SIZE 15
00018 #define BUFFER_SIZE_MEDIAN 5
00019 #define DELAY_BUFFER_MEDIAN 0
00020 
00021 
00022 class Lockin {
00023 public:
00024     // default constructor (untouched!)
00025     // Lockin();
00026     
00027     // initialization of object modes (could have parameters):
00028     void init();
00029     
00030     void initPWM(); //setup the laser and reference signal used by the lockin
00031     void setPWMFrequency(float freq); //change the shared period of the pwm signals
00032     void setLaserPhaseShift(float phaseShift); //change the phase shift of the laser (from 0 to 1)
00033     void setLockinPhaseShift(float phaseShift); //change the phase shift of the lock-in (from 0 to 1)
00034     //future works: 
00035     //add function to change frequency or offset with a potentiometer for exemple
00036     //or scan the best frequency...
00037     
00038     void setLaserPower(bool power); //change PWM settings to turn on/off the laser
00039     
00040     void setADC_forLockin(int mode); //1 set, 0 reset
00041     
00042     unsigned short getSmoothValue(); //return the average of the value stored on the buffer
00043     unsigned short getLastValue(); //return the last conversion of the ADC
00044     unsigned short getMedianValue(); //return the median value of the buffer
00045     //it is just a begining; we can add more complex method for denoising for exemple
00046     //maybe, needs function to start and stop the lockin
00047     
00048     void clearBuffer();
00049     
00050     //can be private
00051     //void catchInterupt(uint32_t value);
00052     
00053     //variables
00054     unsigned short buffer[BUFFER_SIZE];  // does not need to be a float - in fact values are from 0 to 4096 (i.e., 
00055     //unsigned short int buffer[BUFFER_SIZE]; // this is two bytes (0 to 65535)
00056     unsigned short orderedBuffer[BUFFER_SIZE_MEDIAN]; // for computation of the MEDIAN value
00057     int buffer_pos;
00058     
00059     float refFrequency;     // frequency of sensing laser and lock-in (in KHz)
00060     //Phase shift of the pwm signals (from 0 to 1):
00061     //it corresponds to a percentage of the half of a period
00062     //(no phase shift ==> 0% / 90deg phase shift ==> 100%)
00063     float phaseShiftLaser;  // phase shift of the sensing laser 
00064     float phaseShiftLockin; // phase shift of the lock-in reference
00065     
00066     int refFreq; //frequency of the lockin
00067     int offsetRef; //offset between the laser signal and the lockin reference signal
00068     int halfRefFreq;
00069     
00070 private:
00071     // PWM match register value are saved as private 
00072     // to avoid computation when turn on/off for exemple
00073     int _currentMR[6]; 
00074     
00075 
00076 };
00077 
00078 extern Lockin lockin;
00079 
00080 #endif