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VL53L0X working example

 
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PrinceNai



Joined: 31 Oct 2016
Posts: 23

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VL53L0X working example
PostPosted: Sun Jan 21, 2018 12:54 pm     Reply with quote

Hello,

This is the code for vl53l0x ToF sensor. All the files I used in the project are here, just cut them to separate pieces. It isn't polished, so far it just shows the result of a measurement on a LCD. Thanks to the original poster on GitHub here: https://github.com/LILCMU/vl53l0x-ccs

Best regards, Samo


Code:


//******************************************************************************
//   main.c
//******************************************************************************

/* This example shows how to get single-shot range
 measurements from the VL53L0X. The sensor can optionally be
 configured with different ranging profiles, as described in
 the VL53L0X API user manual, to get better performance for
 a certain application. This code is based on the four
 "SingleRanging" examples in the VL53L0X API.
 The range readings are in units of mm.
 
 The original code was found here: https://github.com/LILCMU/vl53l0x-ccs
 Thank you Arnan (Roger) Sipitakiat for porting to CCS.
 
 It is modified to work on 18f252, the result is displayed on LCD.
 

 
 */
//#include <18f252.h>
//#include <Wire.h>

#include <main.h>

#define millis()(msTimer)
int32 msTimer=0;

#include <VL53L0X.h>
#include <VL53L0X.c>
#include <flex_lcd.c>

#INT_TIMER2                   //1ms interrupt
void  TIMER2_isr(void) {
   msTimer++;
}

void pic_setup() {
   setup_timer_2(T2_DIV_BY_16,156,2);      //502 us overflow, 1,0 ms interrupt
   enable_interrupts(INT_TIMER2);
   enable_interrupts(GLOBAL);
   lcd_init();
   lcd_putc('\f');            //CLEAR lcd   
   lcd_gotoxy(1,1);
   delay_ms(100);
}

//*****************************************************************************
// VL53L0X sensor;

// Uncomment this line to use long range mode. This
// increases the sensitivity of the sensor and extends its
// potential range, but increases the likelihood of getting
// an inaccurate reading because of reflections from objects
// other than the intended target. It works best in dark
// conditions.

//#define LONG_RANGE

// Uncomment ONE of these two lines to get
// - higher speed at the cost of lower accuracy OR
// - higher accuracy at the cost of lower speed

//#define HIGH_SPEED
#define HIGH_ACCURACY


void setup()
{

// C5 is connected to XSHUT on a module
   output_low(PIN_C5);          // reset module
   delay_ms(1000);
   output_high(PIN_C5);

//   printf("Starting\r\n");        //original
   
   pic_setup();
   printf(lcd_putc, "Starting...");
   delay_ms(1000);
   init();
   setTimeout(200);

#if defined LONG_RANGE
  // lower the return signal rate limit (default is 0.25 MCPS)
   setSignalRateLimit(0.1);
  // increase laser pulse periods (defaults are 14 and 10 PCLKs)
   setVcselPulsePeriod(VcselPeriodPreRange, 18);
   setVcselPulsePeriod(VcselPeriodFinalRange, 14);
#endif

#if defined HIGH_SPEED
  // reduce timing budget to 20 ms (default is about 33 ms)
   setMeasurementTimingBudget(20000);
#elif defined HIGH_ACCURACY
  // increase timing budget to 200 ms
   setMeasurementTimingBudget(200000);
#endif
}
//*****************************************************************************
void loop()
{
//   printf("%lu\r\n", readRangeSingleMillimeters());
//   if (timeoutOccurred()) { printf(" TIMEOUT\r\n"); }
   delay_us(1);
   printf(lcd_putc,"%lu", readRangeSingleMillimeters());
   if (timeoutOccurred()) {
      delay_us(1);                        // delays of 1us are for debugging purpose only
      printf(lcd_putc, " TIMEOUT....");   // to be done, so far it doesn't timeout
      delay_us(1);
      }
     
   delay_us(1);
}
//*****************************************************************************

void main() {

   setup();
   while(1) {
      delay_ms(200);   
      lcd_putc('\f');            //CLEAR lcd   
      lcd_gotoxy(1,1);
      loop();

   }

}

//******************************************************************************
//   main.h
//******************************************************************************
#include <18F252.h>
#device ADC=16

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES WDT128                   //Watch Dog Timer uses 1:128 Postscale
#FUSES NOBROWNOUT               //No brownout reset
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O

#device ICD=TRUE
#use delay(crystal=20000000)
//#use i2c(Master,SLOW,sda=PIN_C4,scl=PIN_C3,force_hw)
#use i2c(Master,sda=PIN_C4,scl=PIN_C3,force_hw)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

#define RUN_BUTTON PIN_B7     // not used!!!

//******************************************************************************
//   VL53L0X.h
//******************************************************************************
#ifndef VL53L0X_h
#define VL53L0X_h

//#include <Arduino.h>


    // register addresses from API vl53l0x_device.h (ordered as listed there)
    enum regAddr
    {
      SYSRANGE_START                              = 0x00,

      SYSTEM_THRESH_HIGH                          = 0x0C,
      SYSTEM_THRESH_LOW                           = 0x0E,

      SYSTEM_SEQUENCE_CONFIG                      = 0x01,
      SYSTEM_RANGE_CONFIG                         = 0x09,
      SYSTEM_INTERMEASUREMENT_PERIOD              = 0x04,

      SYSTEM_INTERRUPT_CONFIG_GPIO                = 0x0A,

      GPIO_HV_MUX_ACTIVE_HIGH                     = 0x84,

      SYSTEM_INTERRUPT_CLEAR                      = 0x0B,

      RESULT_INTERRUPT_STATUS                     = 0x13,
      RESULT_RANGE_STATUS                         = 0x14,

      RESULT_CORE_AMBIENT_WINDOW_EVENTS_RTN       = 0xBC,
      RESULT_CORE_RANGING_TOTAL_EVENTS_RTN        = 0xC0,
      RESULT_CORE_AMBIENT_WINDOW_EVENTS_REF       = 0xD0,
      RESULT_CORE_RANGING_TOTAL_EVENTS_REF        = 0xD4,
      RESULT_PEAK_SIGNAL_RATE_REF                 = 0xB6,

      ALGO_PART_TO_PART_RANGE_OFFSET_MM           = 0x28,

      I2C_SLAVE_DEVICE_ADDRESS                    = 0x8A,

      MSRC_CONFIG_CONTROL                         = 0x60,

      PRE_RANGE_CONFIG_MIN_SNR                    = 0x27,
      PRE_RANGE_CONFIG_VALID_PHASE_LOW            = 0x56,
      PRE_RANGE_CONFIG_VALID_PHASE_HIGH           = 0x57,
      PRE_RANGE_MIN_COUNT_RATE_RTN_LIMIT          = 0x64,

      FINAL_RANGE_CONFIG_MIN_SNR                  = 0x67,
      FINAL_RANGE_CONFIG_VALID_PHASE_LOW          = 0x47,
      FINAL_RANGE_CONFIG_VALID_PHASE_HIGH         = 0x48,
      FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT = 0x44,

      PRE_RANGE_CONFIG_SIGMA_THRESH_HI            = 0x61,
      PRE_RANGE_CONFIG_SIGMA_THRESH_LO            = 0x62,

      PRE_RANGE_CONFIG_VCSEL_PERIOD               = 0x50,
      PRE_RANGE_CONFIG_TIMEOUT_MACROP_HI          = 0x51,
      PRE_RANGE_CONFIG_TIMEOUT_MACROP_LO          = 0x52,

      SYSTEM_HISTOGRAM_BIN                        = 0x81,
      HISTOGRAM_CONFIG_INITIAL_PHASE_SELECT       = 0x33,
      HISTOGRAM_CONFIG_READOUT_CTRL               = 0x55,

      FINAL_RANGE_CONFIG_VCSEL_PERIOD             = 0x70,
      FINAL_RANGE_CONFIG_TIMEOUT_MACROP_HI        = 0x71,
      FINAL_RANGE_CONFIG_TIMEOUT_MACROP_LO        = 0x72,
      CROSSTALK_COMPENSATION_PEAK_RATE_MCPS       = 0x20,

      MSRC_CONFIG_TIMEOUT_MACROP                  = 0x46,

      SOFT_RESET_GO2_SOFT_RESET_N                 = 0xBF,
      IDENTIFICATION_MODEL_ID                     = 0xC0,
      IDENTIFICATION_REVISION_ID                  = 0xC2,

      OSC_CALIBRATE_VAL                           = 0xF8,

      GLOBAL_CONFIG_VCSEL_WIDTH                   = 0x32,
      GLOBAL_CONFIG_SPAD_ENABLES_REF_0            = 0xB0,
      GLOBAL_CONFIG_SPAD_ENABLES_REF_1            = 0xB1,
      GLOBAL_CONFIG_SPAD_ENABLES_REF_2            = 0xB2,
      GLOBAL_CONFIG_SPAD_ENABLES_REF_3            = 0xB3,
      GLOBAL_CONFIG_SPAD_ENABLES_REF_4            = 0xB4,
      GLOBAL_CONFIG_SPAD_ENABLES_REF_5            = 0xB5,

      GLOBAL_CONFIG_REF_EN_START_SELECT           = 0xB6,
      DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD         = 0x4E,
      DYNAMIC_SPAD_REF_EN_START_OFFSET            = 0x4F,
      POWER_MANAGEMENT_GO1_POWER_FORCE            = 0x80,

      VHV_CONFIG_PAD_SCL_SDA__EXTSUP_HV           = 0x89,

      ALGO_PHASECAL_LIM                           = 0x30,
      ALGO_PHASECAL_CONFIG_TIMEOUT                = 0x30,
    };

    // private variables

    typedef struct
    {
      boolean tcc, msrc, dss, pre_range, final_range;
    } SequenceStepEnables;



    typedef struct
    {
      int16 pre_range_vcsel_period_pclks, final_range_vcsel_period_pclks;

      int16 msrc_dss_tcc_mclks, pre_range_mclks, final_range_mclks;
      int32 msrc_dss_tcc_us,    pre_range_us,    final_range_us;
    } SequenceStepTimeouts;

    void getSequenceStepEnables(SequenceStepEnables * enables);
    void getSequenceStepTimeouts(SequenceStepEnables * enables, SequenceStepTimeouts * timeouts);
   
   
    enum vcselPeriodType { VcselPeriodPreRange, VcselPeriodFinalRange };

    int8 address;
    int16 io_timeout;
    boolean did_timeout;
    int16 timeout_start_ms;

    int8 stop_variable; // read by init and used when starting measurement; is StopVariable field of VL53L0X_DevData_t structure in API
    int32 measurement_timing_budget_us;

    boolean getSpadInfo(int8 * count, boolean * type_is_aperture);

    int8 last_status; // status of last I2C transmission

    VL53L0X(void);

    void setAddress(int8 new_addr);
    int8 getAddress(void) { return address; }

    boolean init(boolean io_2v8 = TRUE);
    #separate boolean init2();

    void writeReg(int8 reg, int8 value);
    void writeReg16Bit(int8 reg, int16 value);
    void writeReg32Bit(int8 reg, int32 value);
    int8 readReg(int8 reg);
    int16 readReg16Bit(int8 reg);
    int32 readReg32Bit(int8 reg);

    void writeMulti(int8 reg, int8  * src, int8 count);
    void readMulti(int8 reg, int8 * dst, int8 count);

    boolean setSignalRateLimit(float limit_Mcps);
    float getSignalRateLimit(void);

    boolean setMeasurementTimingBudget(int32 budget_us);
    int32 getMeasurementTimingBudget(void);

    boolean setVcselPulsePeriod(vcselPeriodType type, int8 period_pclks);
    int8 getVcselPulsePeriod(vcselPeriodType type);

    void startContinuous(int32 period_ms = 0);
    void stopContinuous(void);
    int16 readRangeContinuousMillimeters(void);
    int16 readRangeSingleMillimeters(void);

    void setTimeout(int16 timeout) { io_timeout = timeout; }
    int16 getTimeout(void) { return io_timeout; }
    boolean timeoutOccurred(void);



    boolean performSingleRefCalibration(int8 vhv_init_byte);

    static int16 decodeTimeout(int16 value);
    static int16 encodeTimeout(int16 timeout_mclks);
    static int32 timeoutMclksToMicroseconds(int16 timeout_period_mclks, int8 vcsel_period_pclks);
    static int32 timeoutMicrosecondsToMclks(int32 timeout_period_us, int8 vcsel_period_pclks);


#endif

//******************************************************************************
//   VL53L0X.c
//******************************************************************************

// Most of the functionality of this library is based on the VL53L0X API
// provided by ST (STSW-IMG005), and some of the explanatory comments are quoted
// or paraphrased from the API source code, API user manual (UM2039), and the
// VL53L0X datasheet.

#include <VL53L0X.h>
// #include <Wire.h>

// Defines /////////////////////////////////////////////////////////////////////

// The Arduino two-wire interface uses a 7-bit number for the address,
// and sets the last bit correctly based on reads and writes
//#define ADDRESS_DEFAULT 0b0101001

// 8 bit i2c address
#define ADDRESS_DEFAULT 0b01010010              //0x52


// Record the current time to check an upcoming timeout against
#define startTimeout() (timeout_start_ms = millis())
//#define startTimeout() (timeout_start_ms = 0)

// Check if timeout is enabled (set to nonzero value) and has expired
#define checkTimeoutExpired() (io_timeout > 0 && ((int16)millis() - timeout_start_ms) > io_timeout)

// Decode VCSEL (vertical cavity surface emitting laser) pulse period in PCLKs
// from register value
// based on VL53L0X_decode_vcsel_period()
#define decodeVcselPeriod(reg_val)      (((reg_val) + 1) << 1)

// Encode VCSEL pulse period register value from period in PCLKs
// based on VL53L0X_encode_vcsel_period()
#define encodeVcselPeriod(period_pclks) (((period_pclks) >> 1) - 1)

// Calculate macro period in *nanoseconds* from VCSEL period in PCLKs
// based on VL53L0X_calc_macro_period_ps()
// PLL_period_ps = 1655; macro_period_vclks = 2304
#define calcMacroPeriod(vcsel_period_pclks) ((((int32)2304 * (vcsel_period_pclks) * 1655) + 500) / 1000)

// Constructors ////////////////////////////////////////////////////////////////

// VL53L0X(void)
//   : address(ADDRESS_DEFAULT)
//   , io_timeout(0) // no timeout
//   , did_timeout(false)
// {
// }
//!VL53L0X(void) {
//!  address = (ADDRESS_DEFAULT);
//!  io_timeout =0 ; // no timeout
//!  did_timeout = false;
//!}
// Public Methods //////////////////////////////////////////////////////////////

void setAddress(int8 new_addr)
{
  writeReg(I2C_SLAVE_DEVICE_ADDRESS, new_addr & 0x7F);
  address = new_addr;
}

// Initialize sensor using sequence based on VL53L0X_DataInit(),
// VL53L0X_StaticInit(), and VL53L0X_PerformRefCalibration().
// This function does not perform reference SPAD calibration
// (VL53L0X_PerformRefSpadManagement()), since the API user manual says that it
// is performed by ST on the bare modules; it seems like that should work well
// enough unless a cover glass is added.
// If io_2v8 (optional) is true or not given, the sensor is configured for 2V8
// mode.
boolean init(boolean io_2v8)
{
  // VL53L0X_DataInit() begin
  address = (ADDRESS_DEFAULT);
  io_timeout =0 ; // no timeout
  did_timeout = false;
 
  // sensor uses 1V8 mode for I/O by default; switch to 2V8 mode if necessary
  if (io_2v8)
  {
    writeReg(VHV_CONFIG_PAD_SCL_SDA__EXTSUP_HV,
      readReg(VHV_CONFIG_PAD_SCL_SDA__EXTSUP_HV) | 0x01); // set bit 0
  }

  // "Set I2C standard mode"
  writeReg(0x88, 0x00);

  writeReg(0x80, 0x01);
  writeReg(0xFF, 0x01);
  writeReg(0x00, 0x00);
  stop_variable = readReg(0x91);
  writeReg(0x00, 0x01);
  writeReg(0xFF, 0x00);
  writeReg(0x80, 0x00);

  // disable SIGNAL_RATE_MSRC (bit 1) and SIGNAL_RATE_PRE_RANGE (bit 4) limit checks
  writeReg(MSRC_CONFIG_CONTROL, readReg(MSRC_CONFIG_CONTROL) | 0x12);

  // set final range signal rate limit to 0.25 MCPS (million counts per second)
  setSignalRateLimit(0.25);

  writeReg(SYSTEM_SEQUENCE_CONFIG, 0xFF);

  // VL53L0X_DataInit() end

  // VL53L0X_StaticInit() begin

  int8 spad_count;
  //boolean spad_type_is_aperture;    // boolean can't be used as a pointer
  int8 spad_type_is_aperture;
 
 
 
  if (!getSpadInfo(&spad_count, &spad_type_is_aperture)) { return false; }

  // The SPAD map (RefGoodSpadMap) is read by VL53L0X_get_info_from_device() in
  // the API, but the same data seems to be more easily readable from
  // GLOBAL_CONFIG_SPAD_ENABLES_REF_0 through _6, so read it from there
  int8 ref_spad_map[6];
  readMulti(GLOBAL_CONFIG_SPAD_ENABLES_REF_0, ref_spad_map, 6);

  // -- VL53L0X_set_reference_spads() begin (assume NVM values are valid)

  writeReg(0xFF, 0x01);
  writeReg(DYNAMIC_SPAD_REF_EN_START_OFFSET, 0x00);
  writeReg(DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD, 0x2C);
  writeReg(0xFF, 0x00);
  writeReg(GLOBAL_CONFIG_REF_EN_START_SELECT, 0xB4);

  int8 first_spad_to_enable = spad_type_is_aperture ? 12 : 0; // 12 is the first aperture spad
  int8 spads_enabled = 0;

  for (int8 i = 0; i < 48; i++)
  {
    if (i < first_spad_to_enable || spads_enabled == spad_count)
    {
      // This bit is lower than the first one that should be enabled, or
      // (reference_spad_count) bits have already been enabled, so zero this bit
      ref_spad_map[i / 8] &= ~(1 << (i % 8));
    }
    else if ((ref_spad_map[i / 8] >> (i % 8)) & 0x1)
    {
      spads_enabled++;
    }
  }

  writeMulti(GLOBAL_CONFIG_SPAD_ENABLES_REF_0, ref_spad_map, 6);

  // -- VL53L0X_set_reference_spads() end

  // -- VL53L0X_load_tuning_settings() begin
  // DefaultTuningSettings from vl53l0x_tuning.h

  writeReg(0xFF, 0x01);
  writeReg(0x00, 0x00);

  writeReg(0xFF, 0x00);
  writeReg(0x09, 0x00);
  writeReg(0x10, 0x00);
  writeReg(0x11, 0x00);

  writeReg(0x24, 0x01);
  writeReg(0x25, 0xFF);
  writeReg(0x75, 0x00);

  writeReg(0xFF, 0x01);
  writeReg(0x4E, 0x2C);
  writeReg(0x48, 0x00);
  writeReg(0x30, 0x20);

  writeReg(0xFF, 0x00);
  writeReg(0x30, 0x09);
  writeReg(0x54, 0x00);
  writeReg(0x31, 0x04);
  writeReg(0x32, 0x03);
  writeReg(0x40, 0x83);
  writeReg(0x46, 0x25);
  writeReg(0x60, 0x00);
  writeReg(0x27, 0x00);
  writeReg(0x50, 0x06);
  writeReg(0x51, 0x00);
  writeReg(0x52, 0x96);
  writeReg(0x56, 0x08);
  writeReg(0x57, 0x30);
  writeReg(0x61, 0x00);
  writeReg(0x62, 0x00);
  writeReg(0x64, 0x00);
  writeReg(0x65, 0x00);
  writeReg(0x66, 0xA0);

  writeReg(0xFF, 0x01);
  writeReg(0x22, 0x32);
  writeReg(0x47, 0x14);
  writeReg(0x49, 0xFF);
  writeReg(0x4A, 0x00);

  writeReg(0xFF, 0x00);
  writeReg(0x7A, 0x0A);
  writeReg(0x7B, 0x00);
  writeReg(0x78, 0x21);

  writeReg(0xFF, 0x01);
  writeReg(0x23, 0x34);
  writeReg(0x42, 0x00);
  writeReg(0x44, 0xFF);
  writeReg(0x45, 0x26);
  writeReg(0x46, 0x05);
  writeReg(0x40, 0x40);
  writeReg(0x0E, 0x06);
  writeReg(0x20, 0x1A);
  writeReg(0x43, 0x40);

  writeReg(0xFF, 0x00);
  writeReg(0x34, 0x03);
  writeReg(0x35, 0x44);

  writeReg(0xFF, 0x01);
  writeReg(0x31, 0x04);
  writeReg(0x4B, 0x09);
  writeReg(0x4C, 0x05);
  writeReg(0x4D, 0x04);

  writeReg(0xFF, 0x00);
  writeReg(0x44, 0x00);
  writeReg(0x45, 0x20);
  writeReg(0x47, 0x08);
  writeReg(0x48, 0x28);
  writeReg(0x67, 0x00);
  writeReg(0x70, 0x04);
  writeReg(0x71, 0x01);
  writeReg(0x72, 0xFE);
  writeReg(0x76, 0x00);
  writeReg(0x77, 0x00);

  writeReg(0xFF, 0x01);
  writeReg(0x0D, 0x01);

  writeReg(0xFF, 0x00);
  writeReg(0x80, 0x01);
  writeReg(0x01, 0xF8);

  writeReg(0xFF, 0x01);
  writeReg(0x8E, 0x01);
  writeReg(0x00, 0x01);
  writeReg(0xFF, 0x00);
  writeReg(0x80, 0x00);
 
  return init2();


}


#separate boolean init2() {
  // -- VL53L0X_load_tuning_settings() end

  // "Set interrupt config to new sample ready"
  // -- VL53L0X_SetGpioConfig() begin

  writeReg(SYSTEM_INTERRUPT_CONFIG_GPIO, 0x04);
  writeReg(GPIO_HV_MUX_ACTIVE_HIGH, readReg(GPIO_HV_MUX_ACTIVE_HIGH) & ~0x10); // active low
  writeReg(SYSTEM_INTERRUPT_CLEAR, 0x01);

  // -- VL53L0X_SetGpioConfig() end

  measurement_timing_budget_us = getMeasurementTimingBudget();

  // "Disable MSRC and TCC by default"
  // MSRC = Minimum Signal Rate Check
  // TCC = Target CentreCheck
  // -- VL53L0X_SetSequenceStepEnable() begin

  writeReg(SYSTEM_SEQUENCE_CONFIG, 0xE8);

  // -- VL53L0X_SetSequenceStepEnable() end

  // "Recalculate timing budget"
  setMeasurementTimingBudget(measurement_timing_budget_us);

  // VL53L0X_StaticInit() end

  // VL53L0X_PerformRefCalibration() begin (VL53L0X_perform_ref_calibration())

  // -- VL53L0X_perform_vhv_calibration() begin

  writeReg(SYSTEM_SEQUENCE_CONFIG, 0x01);
  if (!performSingleRefCalibration(0x40)) { return false; }

  // -- VL53L0X_perform_vhv_calibration() end

  // -- VL53L0X_perform_phase_calibration() begin

  writeReg(SYSTEM_SEQUENCE_CONFIG, 0x02);
  if (!performSingleRefCalibration(0x00)) { return false; }

  // -- VL53L0X_perform_phase_calibration() end

  // "restore the previous Sequence Config"
  writeReg(SYSTEM_SEQUENCE_CONFIG, 0xE8);

  // VL53L0X_PerformRefCalibration() end

  return true;
}

// Write an 8-bit register
void writeReg(int8 reg, int8 value)
{
//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!  Wire.write(value);
//!  last_status = Wire.endTransmission();

// IN the Arduino, last_status has the following values
//!0:success
//!1:data too long to fit in transmit buffer
//!2:received NACK on transmit of address
//!3:received NACK on transmit of data
//!4:other error

// In our current port, last_status will only depend on the
// success or failure of the last transmitted byte
// 0 = success, got an ack
// 1 =  no ack (NACK)
// 2 = collision

i2c_start();
i2c_write(address);
i2c_write(reg);
last_status = i2c_write(value);
i2c_stop();

}

// Write a 16-bit register
void writeReg16Bit(int8 reg, int16 value)
{
//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!  Wire.write((value >> 8) & 0xFF); // value high byte
//!  Wire.write( value       & 0xFF); // value low byte
//!  last_status = Wire.endTransmission();
i2c_start();
i2c_write(address);
i2c_write(reg);
i2c_write((value >> 8) & 0xFF);
last_status = i2c_write(value & 0xFF);
i2c_stop();

}

// Write a 32-bit register
void writeReg32Bit(int8 reg, int32 value)
{
//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!  Wire.write((value >> 24) & 0xFF); // value highest byte
//!  Wire.write((value >> 16) & 0xFF);
//!  Wire.write((value >>  8) & 0xFF);
//!  Wire.write( value        & 0xFF); // value lowest byte
//!  last_status = Wire.endTransmission();

i2c_start();
i2c_write(address);
i2c_write(reg);
i2c_write((value >> 24) & 0xFF);
i2c_write((value >> 16) & 0xFF);
i2c_write((value >>  8) & 0xFF);
last_status = i2c_write(value & 0xFF);
i2c_stop();

}

// Read an 8-bit register
int8 readReg(int8 reg)
{
  int8 value;

//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!  last_status = Wire.endTransmission();
//!
//!  Wire.requestFrom(address, (int8)1);
//!  value = Wire.read();
//!

  i2c_start();
  i2c_write(address);
  last_status = i2c_write(reg);
 
  i2c_start();
  i2c_write(address | 1);
  value = i2c_read(0);
 
  return value;

}

// Read a 16-bit register
int16 readReg16Bit(int8 reg)
{
  int16 value;

//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!  last_status = Wire.endTransmission();
//!
//!  Wire.requestFrom(address, (int8)2);
//!  value  = (int16)Wire.read() << 8; // value high byte
//!  value |=           Wire.read();      // value low byte

  i2c_start();
  i2c_write(address);
  last_status = i2c_write(reg);
 
  i2c_start();
  i2c_write(address | 1);
  value = (int16)i2c_read() << 8;
  value |= i2c_read(0);

  return value;
}

// Read a 32-bit register
int32 readReg32Bit(int8 reg)
{
  int32 value;

//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!  last_status = Wire.endTransmission();
//!
//!  Wire.requestFrom(address, (int8)4);
//!  value  = (int32)Wire.read() << 24; // value highest byte
//!  value |= (int32)Wire.read() << 16;
//!  value |= (int16)Wire.read() <<  8;
//!  value |=           Wire.read();       // value lowest byte

  i2c_start();
  i2c_write(address);
  last_status = i2c_write(reg);
 
  i2c_start();
  i2c_write(address | 1);
  value =  (int32)i2c_read() << 24;
  value |= (int32)i2c_read() << 16;
  value |= (int32)i2c_read() << 8;
  value |= i2c_read(0);


  return value;
}

// Write an arbitrary number of bytes from the given array to the sensor,
// starting at the given register
void writeMulti(int8 reg, int8 * src, int8 count)
{
//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!
//!  while (count-- > 0)
//!  {
//!    Wire.write(*(src++));
//!  }
//!
//!  last_status = Wire.endTransmission();

   i2c_start();
   i2c_write(address);
   i2c_write(reg);
   
   while (count-- > 0) {
      last_status = i2c_write(*src++);
   }
   
   i2c_stop();

}

// Read an arbitrary number of bytes from the sensor, starting at the given
// register, into the given array
void readMulti(int8 reg, int8 * dst, int8 count)
{
//!  Wire.beginTransmission(address);
//!  Wire.write(reg);
//!  last_status = Wire.endTransmission();
//!
//!  Wire.requestFrom(address, count);
//!
//!  while (count-- > 0)
//!  {
//!    *(dst++) = Wire.read();
//!  }

   i2c_start();
   i2c_write(address);
   last_status = i2c_write(reg);
   
   i2c_start();
   i2c_write(address|1);
   while (count-- > 1) {
      *(dst++) = i2c_read();
   }
   *(dst++) = i2c_read(0);

   i2c_stop();


}

// Set the return signal rate limit check value in units of MCPS (mega counts
// per second). "This represents the amplitude of the signal reflected from the
// target and detected by the device"; setting this limit presumably determines
// the minimum measurement necessary for the sensor to report a valid reading.
// Setting a lower limit increases the potential range of the sensor but also
// seems to increase the likelihood of getting an inaccurate reading because of
// unwanted reflections from objects other than the intended target.
// Defaults to 0.25 MCPS as initialized by the ST API and this library.
boolean setSignalRateLimit(float limit_Mcps)
{
  if (limit_Mcps < 0 || limit_Mcps > 511.99) { return false; }

  // Q9.7 fixed point format (9 integer bits, 7 fractional bits)
  writeReg16Bit(FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT, limit_Mcps * (1 << 7));
  return true;
}

// Get the return signal rate limit check value in MCPS
float getSignalRateLimit(void)
{
  return (float)readReg16Bit(FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT) / (1 << 7);
}

// Set the measurement timing budget in microseconds, which is the time allowed
// for one measurement; the ST API and this library take care of splitting the
// timing budget among the sub-steps in the ranging sequence. A longer timing
// budget allows for more accurate measurements. Increasing the budget by a
// factor of N decreases the range measurement standard deviation by a factor of
// sqrt(N). Defaults to about 33 milliseconds; the minimum is 20 ms.
// based on VL53L0X_set_measurement_timing_budget_micro_seconds()
boolean setMeasurementTimingBudget(int32 budget_us)
{
  SequenceStepEnables enables;
  SequenceStepTimeouts timeouts;

  int16 const StartOverhead      = 1320; // note that this is different than the value in get_
  int16 const EndOverhead        = 960;
  int16 const MsrcOverhead       = 660;
  int16 const TccOverhead        = 590;
  int16 const DssOverhead        = 690;
  int16 const PreRangeOverhead   = 660;
  int16 const FinalRangeOverhead = 550;

  int32 const MinTimingBudget = 20000;

  if (budget_us < MinTimingBudget) { return false; }

  int32 used_budget_us = StartOverhead + EndOverhead;

  getSequenceStepEnables(&enables);
  getSequenceStepTimeouts(&enables, &timeouts);

  if (enables.tcc)
  {
    used_budget_us += (timeouts.msrc_dss_tcc_us + TccOverhead);
  }

  if (enables.dss)
  {
    used_budget_us += 2 * (timeouts.msrc_dss_tcc_us + DssOverhead);
  }
  else if (enables.msrc)
  {
    used_budget_us += (timeouts.msrc_dss_tcc_us + MsrcOverhead);
  }

  if (enables.pre_range)
  {
    used_budget_us += (timeouts.pre_range_us + PreRangeOverhead);
  }

  if (enables.final_range)
  {
    used_budget_us += FinalRangeOverhead;

    // "Note that the final range timeout is determined by the timing
    // budget and the sum of all other timeouts within the sequence.
    // If there is no room for the final range timeout, then an error
    // will be set. Otherwise the remaining time will be applied to
    // the final range."

    if (used_budget_us > budget_us)
    {
      // "Requested timeout too big."
      return false;
    }

    int32 final_range_timeout_us = budget_us - used_budget_us;

    // set_sequence_step_timeout() begin
    // (SequenceStepId == VL53L0X_SEQUENCESTEP_FINAL_RANGE)

    // "For the final range timeout, the pre-range timeout
    //  must be added. To do this both final and pre-range
    //  timeouts must be expressed in macro periods MClks
    //  because they have different vcsel periods."

    int16 final_range_timeout_mclks =
      timeoutMicrosecondsToMclks(final_range_timeout_us,
                                 timeouts.final_range_vcsel_period_pclks);

    if (enables.pre_range)
    {
      final_range_timeout_mclks += timeouts.pre_range_mclks;
    }

    writeReg16Bit(FINAL_RANGE_CONFIG_TIMEOUT_MACROP_HI,
      encodeTimeout(final_range_timeout_mclks));

    // set_sequence_step_timeout() end

    measurement_timing_budget_us = budget_us; // store for internal reuse
  }
  return true;
}

// Get the measurement timing budget in microseconds
// based on VL53L0X_get_measurement_timing_budget_micro_seconds()
// in us
int32 getMeasurementTimingBudget(void)
{
  SequenceStepEnables enables;
  SequenceStepTimeouts timeouts;

  int16 const StartOverhead     = 1910; // note that this is different than the value in set_
  int16 const EndOverhead        = 960;
  int16 const MsrcOverhead       = 660;
  int16 const TccOverhead        = 590;
  int16 const DssOverhead        = 690;
  int16 const PreRangeOverhead   = 660;
  int16 const FinalRangeOverhead = 550;

  // "Start and end overhead times always present"
  int32 budget_us = StartOverhead + EndOverhead;

  getSequenceStepEnables(&enables);
  getSequenceStepTimeouts(&enables, &timeouts);

  if (enables.tcc)
  {
    budget_us += (timeouts.msrc_dss_tcc_us + TccOverhead);
  }

  if (enables.dss)
  {
    budget_us += 2 * (timeouts.msrc_dss_tcc_us + DssOverhead);
  }
  else if (enables.msrc)
  {
    budget_us += (timeouts.msrc_dss_tcc_us + MsrcOverhead);
  }

  if (enables.pre_range)
  {
    budget_us += (timeouts.pre_range_us + PreRangeOverhead);
  }

  if (enables.final_range)
  {
    budget_us += (timeouts.final_range_us + FinalRangeOverhead);
  }

  measurement_timing_budget_us = budget_us; // store for internal reuse
  return budget_us;
}

// Set the VCSEL (vertical cavity surface emitting laser) pulse period for the
// given period type (pre-range or final range) to the given value in PCLKs.
// Longer periods seem to increase the potential range of the sensor.
// Valid values are (even numbers only):
//  pre:  12 to 18 (initialized default: 14)
//  final: 8 to 14 (initialized default: 10)
// based on VL53L0X_set_vcsel_pulse_period()
boolean setVcselPulsePeriod(vcselPeriodType type, int8 period_pclks)
{
  int8 vcsel_period_reg = encodeVcselPeriod(period_pclks);

  SequenceStepEnables enables;
  SequenceStepTimeouts timeouts;

  getSequenceStepEnables(&enables);
  getSequenceStepTimeouts(&enables, &timeouts);

  // "Apply specific settings for the requested clock period"
  // "Re-calculate and apply timeouts, in macro periods"

  // "When the VCSEL period for the pre or final range is changed,
  // the corresponding timeout must be read from the device using
  // the current VCSEL period, then the new VCSEL period can be
  // applied. The timeout then must be written back to the device
  // using the new VCSEL period.
  //
  // For the MSRC timeout, the same applies - this timeout being
  // dependant on the pre-range vcsel period."


  if (type == VcselPeriodPreRange)
  {
    // "Set phase check limits"
    switch (period_pclks)
    {
      case 12:
        writeReg(PRE_RANGE_CONFIG_VALID_PHASE_HIGH, 0x18);
        break;

      case 14:
        writeReg(PRE_RANGE_CONFIG_VALID_PHASE_HIGH, 0x30);
        break;

      case 16:
        writeReg(PRE_RANGE_CONFIG_VALID_PHASE_HIGH, 0x40);
        break;

      case 18:
        writeReg(PRE_RANGE_CONFIG_VALID_PHASE_HIGH, 0x50);
        break;

      default:
        // invalid period
        return false;
    }
    writeReg(PRE_RANGE_CONFIG_VALID_PHASE_LOW, 0x08);

    // apply new VCSEL period
    writeReg(PRE_RANGE_CONFIG_VCSEL_PERIOD, vcsel_period_reg);

    // update timeouts

    // set_sequence_step_timeout() begin
    // (SequenceStepId == VL53L0X_SEQUENCESTEP_PRE_RANGE)

    int16 new_pre_range_timeout_mclks =
      timeoutMicrosecondsToMclks(timeouts.pre_range_us, period_pclks);

    writeReg16Bit(PRE_RANGE_CONFIG_TIMEOUT_MACROP_HI,
      encodeTimeout(new_pre_range_timeout_mclks));

    // set_sequence_step_timeout() end

    // set_sequence_step_timeout() begin
    // (SequenceStepId == VL53L0X_SEQUENCESTEP_MSRC)

    int16 new_msrc_timeout_mclks =
      timeoutMicrosecondsToMclks(timeouts.msrc_dss_tcc_us, period_pclks);

    writeReg(MSRC_CONFIG_TIMEOUT_MACROP,
      (new_msrc_timeout_mclks > 256) ? 255 : (new_msrc_timeout_mclks - 1));

    // set_sequence_step_timeout() end
  }
  else if (type == VcselPeriodFinalRange)
  {
    switch (period_pclks)
    {
      case 8:
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_HIGH, 0x10);
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_LOW,  0x08);
        writeReg(GLOBAL_CONFIG_VCSEL_WIDTH, 0x02);
        writeReg(ALGO_PHASECAL_CONFIG_TIMEOUT, 0x0C);
        writeReg(0xFF, 0x01);
        writeReg(ALGO_PHASECAL_LIM, 0x30);
        writeReg(0xFF, 0x00);
        break;

      case 10:
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_HIGH, 0x28);
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_LOW,  0x08);
        writeReg(GLOBAL_CONFIG_VCSEL_WIDTH, 0x03);
        writeReg(ALGO_PHASECAL_CONFIG_TIMEOUT, 0x09);
        writeReg(0xFF, 0x01);
        writeReg(ALGO_PHASECAL_LIM, 0x20);
        writeReg(0xFF, 0x00);
        break;

      case 12:
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_HIGH, 0x38);
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_LOW,  0x08);
        writeReg(GLOBAL_CONFIG_VCSEL_WIDTH, 0x03);
        writeReg(ALGO_PHASECAL_CONFIG_TIMEOUT, 0x08);
        writeReg(0xFF, 0x01);
        writeReg(ALGO_PHASECAL_LIM, 0x20);
        writeReg(0xFF, 0x00);
        break;

      case 14:
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_HIGH, 0x48);
        writeReg(FINAL_RANGE_CONFIG_VALID_PHASE_LOW,  0x08);
        writeReg(GLOBAL_CONFIG_VCSEL_WIDTH, 0x03);
        writeReg(ALGO_PHASECAL_CONFIG_TIMEOUT, 0x07);
        writeReg(0xFF, 0x01);
        writeReg(ALGO_PHASECAL_LIM, 0x20);
        writeReg(0xFF, 0x00);
        break;

      default:
        // invalid period
        return false;
    }

    // apply new VCSEL period
    writeReg(FINAL_RANGE_CONFIG_VCSEL_PERIOD, vcsel_period_reg);

    // update timeouts

    // set_sequence_step_timeout() begin
    // (SequenceStepId == VL53L0X_SEQUENCESTEP_FINAL_RANGE)

    // "For the final range timeout, the pre-range timeout
    //  must be added. To do this both final and pre-range
    //  timeouts must be expressed in macro periods MClks
    //  because they have different vcsel periods."

    int16 new_final_range_timeout_mclks =
      timeoutMicrosecondsToMclks(timeouts.final_range_us, period_pclks);

    if (enables.pre_range)
    {
      new_final_range_timeout_mclks += timeouts.pre_range_mclks;
    }

    writeReg16Bit(FINAL_RANGE_CONFIG_TIMEOUT_MACROP_HI,
      encodeTimeout(new_final_range_timeout_mclks));

    // set_sequence_step_timeout end
  }
  else
  {
    // invalid type
    return false;
  }

  // "Finally, the timing budget must be re-applied"

  setMeasurementTimingBudget(measurement_timing_budget_us);

  // "Perform the phase calibration. This is needed after changing on vcsel period."
  // VL53L0X_perform_phase_calibration() begin

  int8 sequence_config = readReg(SYSTEM_SEQUENCE_CONFIG);
  writeReg(SYSTEM_SEQUENCE_CONFIG, 0x02);
  performSingleRefCalibration(0x0);
  writeReg(SYSTEM_SEQUENCE_CONFIG, sequence_config);

  // VL53L0X_perform_phase_calibration() end

  return true;
}

// Get the VCSEL pulse period in PCLKs for the given period type.
// based on VL53L0X_get_vcsel_pulse_period()
int8 getVcselPulsePeriod(vcselPeriodType type)
{
  if (type == VcselPeriodPreRange)
  {
    return decodeVcselPeriod(readReg(PRE_RANGE_CONFIG_VCSEL_PERIOD));
  }
  else if (type == VcselPeriodFinalRange)
  {
    return decodeVcselPeriod(readReg(FINAL_RANGE_CONFIG_VCSEL_PERIOD));
  }
  else { return 255; }
}

// Start continuous ranging measurements. If period_ms (optional) is 0 or not
// given, continuous back-to-back mode is used (the sensor takes measurements as
// often as possible); otherwise, continuous timed mode is used, with the given
// inter-measurement period in milliseconds determining how often the sensor
// takes a measurement.
// based on VL53L0X_StartMeasurement()
void startContinuous(int32 period_ms)
{
  writeReg(0x80, 0x01);
  writeReg(0xFF, 0x01);
  writeReg(0x00, 0x00);
  writeReg(0x91, stop_variable);
  writeReg(0x00, 0x01);
  writeReg(0xFF, 0x00);
  writeReg(0x80, 0x00);

  if (period_ms != 0)
  {
    // continuous timed mode

    // VL53L0X_SetInterMeasurementPeriodMilliSeconds() begin

    int16 osc_calibrate_val = readReg16Bit(OSC_CALIBRATE_VAL);

    if (osc_calibrate_val != 0)
    {
      period_ms *= osc_calibrate_val;
    }

    writeReg32Bit(SYSTEM_INTERMEASUREMENT_PERIOD, period_ms);

    // VL53L0X_SetInterMeasurementPeriodMilliSeconds() end

    writeReg(SYSRANGE_START, 0x04); // VL53L0X_REG_SYSRANGE_MODE_TIMED
  }
  else
  {
    // continuous back-to-back mode
    writeReg(SYSRANGE_START, 0x02); // VL53L0X_REG_SYSRANGE_MODE_BACKTOBACK
  }
}

// Stop continuous measurements
// based on VL53L0X_StopMeasurement()
void stopContinuous(void)
{
  writeReg(SYSRANGE_START, 0x01); // VL53L0X_REG_SYSRANGE_MODE_SINGLESHOT

  writeReg(0xFF, 0x01);
  writeReg(0x00, 0x00);
  writeReg(0x91, 0x00);
  writeReg(0x00, 0x01);
  writeReg(0xFF, 0x00);
}

// Returns a range reading in millimeters when continuous mode is active
// (readRangeSingleMillimeters() also calls this function after starting a
// single-shot range measurement)
int16 readRangeContinuousMillimeters(void)
{
  startTimeout();
  while ((readReg(RESULT_INTERRUPT_STATUS) & 0x07) == 0)
  {
    if (checkTimeoutExpired())
    {
      did_timeout = true;
      return 65535;
    }
  }

  // assumptions: Linearity Corrective Gain is 1000 (default);
  // fractional ranging is not enabled
  int16 range = readReg16Bit(RESULT_RANGE_STATUS + 10);

  writeReg(SYSTEM_INTERRUPT_CLEAR, 0x01);

  return range;
}

// Performs a single-shot range measurement and returns the reading in
// millimeters
// based on VL53L0X_PerformSingleRangingMeasurement()
int16 readRangeSingleMillimeters(void)
{
  writeReg(0x80, 0x01);
  writeReg(0xFF, 0x01);
  writeReg(0x00, 0x00);
  writeReg(0x91, stop_variable);
  writeReg(0x00, 0x01);
  writeReg(0xFF, 0x00);
  writeReg(0x80, 0x00);

  writeReg(SYSRANGE_START, 0x01);

  // "Wait until start bit has been cleared"
  startTimeout();
  while (readReg(SYSRANGE_START) & 0x01)
  {
    if (checkTimeoutExpired())
    {
      did_timeout = true;
      return 65535;
    }
  }

  return readRangeContinuousMillimeters();
}

// Did a timeout occur in one of the read functions since the last call to
// timeoutOccurred()?
boolean timeoutOccurred()
{
  boolean tmp = did_timeout;
  did_timeout = false;
  return tmp;
}

// Private Methods /////////////////////////////////////////////////////////////

// Get reference SPAD (single photon avalanche diode) count and type
// based on VL53L0X_get_info_from_device(),
// but only gets reference SPAD count and type
boolean getSpadInfo(int8 * count, boolean * type_is_aperture)
{
  int8 tmp;

  writeReg(0x80, 0x01);
  writeReg(0xFF, 0x01);
  writeReg(0x00, 0x00);

  writeReg(0xFF, 0x06);
  writeReg(0x83, readReg(0x83) | 0x04);
  writeReg(0xFF, 0x07);
  writeReg(0x81, 0x01);

  writeReg(0x80, 0x01);

  writeReg(0x94, 0x6b);
  writeReg(0x83, 0x00);
  startTimeout();
  while (readReg(0x83) == 0x00)
  {
    if (checkTimeoutExpired()) { return false; }
  }
  writeReg(0x83, 0x01);
  tmp = readReg(0x92);

  *count = tmp & 0x7f;
  *type_is_aperture = (tmp >> 7) & 0x01;

  writeReg(0x81, 0x00);
  writeReg(0xFF, 0x06);
  writeReg(0x83, readReg( 0x83  & ~0x04));
  writeReg(0xFF, 0x01);
  writeReg(0x00, 0x01);

  writeReg(0xFF, 0x00);
  writeReg(0x80, 0x00);

  return true;
}

// Get sequence step enables
// based on VL53L0X_GetSequenceStepEnables()
void getSequenceStepEnables(SequenceStepEnables * enables)
{
  int8 sequence_config = readReg(SYSTEM_SEQUENCE_CONFIG);

  enables->tcc          = (sequence_config >> 4) & 0x1;
  enables->dss          = (sequence_config >> 3) & 0x1;
  enables->msrc         = (sequence_config >> 2) & 0x1;
  enables->pre_range    = (sequence_config >> 6) & 0x1;
  enables->final_range  = (sequence_config >> 7) & 0x1;
}

// Get sequence step timeouts
// based on get_sequence_step_timeout(),
// but gets all timeouts instead of just the requested one, and also stores
// intermediate values
void getSequenceStepTimeouts(SequenceStepEnables  * enables, SequenceStepTimeouts * timeouts)
{
  timeouts->pre_range_vcsel_period_pclks = getVcselPulsePeriod(VcselPeriodPreRange);

  timeouts->msrc_dss_tcc_mclks = readReg(MSRC_CONFIG_TIMEOUT_MACROP) + 1;
  timeouts->msrc_dss_tcc_us =
    timeoutMclksToMicroseconds(timeouts->msrc_dss_tcc_mclks,
                               timeouts->pre_range_vcsel_period_pclks);

  timeouts->pre_range_mclks =
    decodeTimeout(readReg16Bit(PRE_RANGE_CONFIG_TIMEOUT_MACROP_HI));
  timeouts->pre_range_us =
    timeoutMclksToMicroseconds(timeouts->pre_range_mclks,
                               timeouts->pre_range_vcsel_period_pclks);

  timeouts->final_range_vcsel_period_pclks = getVcselPulsePeriod(VcselPeriodFinalRange);

  timeouts->final_range_mclks =
    decodeTimeout(readReg16Bit(FINAL_RANGE_CONFIG_TIMEOUT_MACROP_HI));

  if (enables->pre_range)
  {
    timeouts->final_range_mclks -= timeouts->pre_range_mclks;
  }

  timeouts->final_range_us =
    timeoutMclksToMicroseconds(timeouts->final_range_mclks,
                               timeouts->final_range_vcsel_period_pclks);
}

// Decode sequence step timeout in MCLKs from register value
// based on VL53L0X_decode_timeout()
// Note: the original function returned a int32, but the return value is
// always stored in a int16.
int16 decodeTimeout(int16 reg_val)
{
  // format: "(LSByte * 2^MSByte) + 1"
  return (int16)((reg_val & 0x00FF) <<
         (int16)((reg_val & 0xFF00) >> 8)) + 1;
}

// Encode sequence step timeout register value from timeout in MCLKs
// based on VL53L0X_encode_timeout()
// Note: the original function took a int16, but the argument passed to it
// is always a int16.
int16 encodeTimeout(int16 timeout_mclks)
{
  // format: "(LSByte * 2^MSByte) + 1"

  int32 ls_byte = 0;
  int16 ms_byte = 0;

  if (timeout_mclks > 0)
  {
    ls_byte = timeout_mclks - 1;

    while ((ls_byte & 0xFFFFFF00) > 0)
    {
      ls_byte >>= 1;
      ms_byte++;
    }

    return (ms_byte << 8) | (ls_byte & 0xFF);
  }
  else { return 0; }
}

// Convert sequence step timeout from MCLKs to microseconds with given VCSEL period in PCLKs
// based on VL53L0X_calc_timeout_us()
int32 timeoutMclksToMicroseconds(int16 timeout_period_mclks, int8 vcsel_period_pclks)
{
  int32 macro_period_ns = calcMacroPeriod(vcsel_period_pclks);

  return ((timeout_period_mclks * macro_period_ns) + (macro_period_ns / 2)) / 1000;
}

// Convert sequence step timeout from microseconds to MCLKs with given VCSEL period in PCLKs
// based on VL53L0X_calc_timeout_mclks()
int32 timeoutMicrosecondsToMclks(int32 timeout_period_us, int8 vcsel_period_pclks)
{
  int32 macro_period_ns = calcMacroPeriod(vcsel_period_pclks);

  return (((timeout_period_us * 1000) + (macro_period_ns / 2)) / macro_period_ns);
}


// based on VL53L0X_perform_single_ref_calibration()
boolean performSingleRefCalibration(int8 vhv_init_byte)
{
  writeReg(SYSRANGE_START, 0x01 | vhv_init_byte); // VL53L0X_REG_SYSRANGE_MODE_START_STOP

  startTimeout();
  while ((readReg(RESULT_INTERRUPT_STATUS) & 0x07) == 0)
  {
    if (checkTimeoutExpired()) { return false; }
  }

  writeReg(SYSTEM_INTERRUPT_CLEAR, 0x01);

  writeReg(SYSRANGE_START, 0x00);

  return true;
}


//!void main() {
//!   delay_ms(1000);
//!   init();
//!
//!}

//******************************************************************************
//   flex_lcd.c
//******************************************************************************


// flex_lcd.c

// These pins are for the Microchip PicDem2-Plus board,
// which is what I used to test the driver.  Change these
// pins to fit your own board.
// changed for my setup
#define LCD_DB4   PIN_B2
#define LCD_DB5   PIN_B3
#define LCD_DB6   PIN_B4
#define LCD_DB7   PIN_B5

#define LCD_E     PIN_A3
#define LCD_RS    PIN_B1
//#define LCD_RW    PIN_A2

// If you only want a 6-pin interface to your LCD, then
// connect the R/W pin on the LCD to ground, and comment
// out the following line.

//#define USE_LCD_RW   1     

//========================================
//#device PIC18F252
#define lcd_type 2        // 0=5x7, 1=5x10, 2=2 lines
#define lcd_line_two 0x40 // LCD RAM address for the 2nd line


int8 const LCD_INIT_STRING[4] =
{
 0x20 | (lcd_type << 2), // Func set: 4-bit, 2 lines, 5x8 dots
 0xc,                    // Display on
 1,                      // Clear display
 6                       // Increment cursor
 };


//-------------------------------------
void lcd_send_nibble(int8 nibble)
{
// Note:  !! converts an integer expression
// to a boolean (1 or 0).
 output_bit(LCD_DB4, !!(nibble & 1));
 output_bit(LCD_DB5, !!(nibble & 2));
 output_bit(LCD_DB6, !!(nibble & 4));   
 output_bit(LCD_DB7, !!(nibble & 8));   

 delay_cycles(1);
 output_high(LCD_E);
 delay_us(2);
 output_low(LCD_E);
}

//-----------------------------------
// This sub-routine is only called by lcd_read_byte().
// It's not a stand-alone routine.  For example, the
// R/W signal is set high by lcd_read_byte() before
// this routine is called.     

#ifdef USE_LCD_RW
int8 lcd_read_nibble(void)
{
int8 retval;
// Create bit variables so that we can easily set
// individual bits in the retval variable.
#bit retval_0 = retval.0
#bit retval_1 = retval.1
#bit retval_2 = retval.2
#bit retval_3 = retval.3

retval = 0;
   
output_high(LCD_E);
delay_cycles(1);

retval_0 = input(LCD_DB4);
retval_1 = input(LCD_DB5);
retval_2 = input(LCD_DB6);
retval_3 = input(LCD_DB7);
 
output_low(LCD_E);
   
return(retval);   
}   
#endif

//---------------------------------------
// Read a byte from the LCD and return it.

#ifdef USE_LCD_RW
int8 lcd_read_byte(void)
{
int8 low;
int8 high;

output_high(LCD_RW);
delay_cycles(1);

high = lcd_read_nibble();

low = lcd_read_nibble();

return( (high<<4) | low);
}
#endif

//----------------------------------------
// Send a byte to the LCD.
void lcd_send_byte(int8 address, int8 n)
{
output_low(LCD_RS);

#ifdef USE_LCD_RW
while(bit_test(lcd_read_byte(),7)) ;
#else
delay_us(60);
#endif

if(address)
   output_high(LCD_RS);
else
   output_low(LCD_RS);
     
 delay_cycles(1);

#ifdef USE_LCD_RW
output_low(LCD_RW);
delay_cycles(1);
#endif

output_low(LCD_E);

lcd_send_nibble(n >> 4);
lcd_send_nibble(n & 0xf);
}

//----------------------------
void lcd_init(void)
{
int8 i;

output_low(LCD_RS);

#ifdef USE_LCD_RW
output_low(LCD_RW);
#endif

output_low(LCD_E);

delay_ms(15);

for(i=0 ;i < 3; i++)
   {
    lcd_send_nibble(0x03);
    delay_ms(5);
   }

lcd_send_nibble(0x02);

for(i=0; i < sizeof(LCD_INIT_STRING); i++)
   {
    lcd_send_byte(0, LCD_INIT_STRING[i]);
   
    // If the R/W signal is not used, then
    // the busy bit can't be polled.  One of
    // the init commands takes longer than
    // the hard-coded delay of 60 us, so in
    // that case, lets just do a 5 ms delay
    // after all four of them.
    #ifndef USE_LCD_RW
    delay_ms(5);
    #endif
   }

}

//----------------------------

void lcd_gotoxy(int8 x, int8 y)
{
int8 address;

if(y != 1)
   address = lcd_line_two;
else
   address=0;

address += x-1;
lcd_send_byte(0, 0x80 | address);
}

//-----------------------------
void lcd_putc(char c)
{
 switch(c)
   {
    case '\f':
      lcd_send_byte(0,1);
      delay_ms(2);
      break;
   
    case '\n':
       lcd_gotoxy(1,2);
       break;
   
    case '\b':
       lcd_send_byte(0,0x10);
       break;
   
    default:
       lcd_send_byte(1,c);
       break;
   }
}

//------------------------------
#ifdef USE_LCD_RW
char lcd_getc(int8 x, int8 y)
{
char value;

lcd_gotoxy(x,y);

// Wait until busy flag is low.
while(bit_test(lcd_read_byte(),7));

output_high(LCD_RS);
value = lcd_read_byte();
output_low(lcd_RS);

return(value);
}
#endif
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