File content as of revision 13:7fc157a0187d:

/*  
 * Copyright (c) Eric Tsai 2017
 *
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 *
 * Credit: started with the basic BLE Temperature Beacon code from mbed Bluetooth Low Energy team
 * https://developer.mbed.org/teams/Bluetooth-Low-Energy/code/BLE_TemperatureBeacon/file/0a8bbb6dea16/main.cpp
 *
 * BLE sensor as Beacon advertisements.  Intended to function with specific BLE observer.
 * Tested on nRF51822 targets on mbed.
 * keywords:  todo, tochange
*/


extern "C"
{
   #include "nrf_ecb.h"  //required to call the ecb functions for encryption
}
 
#include "mbed.h"
#include "toolchain.h"
#include "ble/BLE.h"
//#include "TMP_nrf51/TMP_nrf51.h"
//#include "TMP102.h"
#include "VL6180.h" //https://developer.mbed.org/users/sburg/code/VL6180/
//https://developer.mbed.org/users/sburg/notebook/vl6180-time-of-flight-range-finder/

/*******************************************************************************************
 * START tochange: items that may need customization depending on sensors, hardware, and desired behavior
*******************************************************************************************/
uint16_t Periodic_Update_Seconds = 10; //number of seconds between periodic I/O status re-transmits 900s =15 min.
#define MyDebugEnb 0  //enables serial output for debug, consumes ~1mA when idle
uint8_t magnet_near=0;  //this I/O, specifically for reed switch sensor
//TMP102 tempI2C(p0, p1, 0x90);
//VL6180 rf(p12, p15); //I2C purple board sda=p12, scl=p15
VL6180 rf(p9, p11); //I2C purple board sda=p12, scl=p15
//DigitalOut pinHandShake(p0);  //shutdown pin
//VL6180 rf(p12, p15); //I2C sda=P0 and scl=p1
/* hardware interrupt pins, selected based on hardware
 *Syntax:  Pin "P0.4" on nRF51822 documentation is mbed "p4".
 * InterruptIn is pulled-up.  GND the pin to activate.
*/
InterruptIn button1(p0);    //nRF51822 P0.0
InterruptIn button2(p1);    //nRF51822 P0.1


/******************************************************************************************
 * END tochange
*******************************************************************************************/


#if MyDebugEnb
// if you see ~1mA consumption during sleep, that's because MyDebugEnb==1, it's enabled.
Serial device(p9, p11);  //nRF51822 uart :  TX=p9.  RX=p11
#endif

static Ticker Tic_Stop_Adv;   //used to stop advertising after X seconds
static Ticker Tic_Debounce; //debounce I/O
static Ticker Tic_Periodic; //transmit sensor data on a periodic basis outside I/O events

const uint16_t Periodicity = 1800;   //birthday periodicity used for spoof checking, must match gateway. Should be 1800 seconds for 30minutes
static Timer Tmr_From_Birthday;  //holds number of seconds since birthday, for spoof detection
static Ticker Tic_Birthday; //resets Tmr_From_Birthday every Periodicity seconds, for spoof detection


static bool Flag_Update_IO = false;  //flag to indicate event is hardware interrupt
static bool Flag_Periodic_Call = false;  //flag to indicate event is periodic callback
static bool Flag_Detach_Adv_Tic = false;  //flag to stop advertising

/* Optional: Device Name, add for human read-ability */
const static char     DEVICE_NAME[] = "LOL";


//Advertisement Data
//note:  AdvData[] holds bytes [5] to byte [30] of entire advertising data.  The user content part after ADV flag and header
static uint8_t AdvData[] = {0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0};  //26 Bytes manufacturer specific data
char buffer[10]={0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; //hold I/O reading json
char bat_volt_char[6] = {0, 0, 0, 0, 0, 0}; //hold json for battery reading
uint8_t Adv_First_Section[10];  //holds the first several bytes with a pattern indicating this sensor is "one of ours" 
uint8_t mac_reverse[6] = {0x0,0x0,0x0,0x0,0x0,0x0};  //mac address for this module
char sensor_char[8] = {0, 0, 0, 0, 0, 0}; //hold json for temperature

/*****  Advertisement structure is 31 Bytes  ****************

https://docs.mbed.com/docs/ble-intros/en/latest/Advanced/CustomGAP/

Full Advertisement:
First 5 bytes are set by stack according to flag and header parameters.
Last 26 bytes are user data
-- tabbed --
Byte 0  |   AD1 Length  |       0x02    |   AD1 is 2 bytes long
Byte 1  |   AD1 Type    |       0x01    |   AD1 Data interpreted as flag
Byte 2  |   AD1 Data 0  |       0x06    |   AD1 Data flag mean "00000110"
Byte 3  |   AD2 Length  |       0x1B    |   AD2 is 27 bytes (0x1B) long (rest of this data)
Byte 4  |   AD2 Type    |       0xFF    |   0xFF mean Manufacturer Specific Data
Byte 5  |   AD2 Data 0  |   ADV_Data[0] |   "our device" flag, MAC[3]
Byte 6  |   AD2 Data 1  |   ADV_Data[1] |   "out device" flag, MAC[2]
Byte 7  |   AD2 Data 2  |   ADV_Data[2] |   "out device" flag, MAC[1]
Byte 8  |   AD2 Data 3  |   ADV_Data[3] |   "out device" flag, MAC[0]
Byte 9  |   AD2 Data 4  |   ADV_Data[4] |   battery voltage json MSB, ie 3 in 3.14
Byte 10 |   AD2 Data 5  |   ADV_Data[5] |   battery voltage json
Byte 11 |   AD2 Data 6  |   ADV_Data[6] |   battery voltage json
Byte 12 |   AD2 Data 7  |   ADV_Data[7] |   battery voltage json LSB, ie 4 in 3.14
Byte 13 |   AD2 Data 8  |   ADV_Data[8] |   reserved
Byte 14 |   AD2 Data 9  |   ADV_Data[9] |   reserved
Byte 15 |   AD2 Data 10 |   ADV_Data[10] Encrypted  |   spoof - clock high byte, range 0 to 1800 seconds
Byte 16 |   AD2 Data 11 |   ADV_Data[11] Encrypted  |   spoof - clock low byte
Byte 17 |   AD2 Data 12 |   ADV_Data[12] Encrypted  |   Xmit_Cnt - increments per transmit event, 0-255
Byte 18 |   AD2 Data 13 |   ADV_Data[13] Encrypted  |   JSON[0]
Byte 19 |   AD2 Data 14 |   ADV_Data[14] Encrypted  |   JSON[1]
Byte 20 |   AD2 Data 15 |   ADV_Data[15] Encrypted  |   JSON[2]
Byte 21 |   AD2 Data 16 |   ADV_Data[16] Encrypted  |   JSON[3]
Byte 22 |   AD2 Data 17 |   ADV_Data[17] Encrypted  |   JSON[4]
Byte 23 |   AD2 Data 18 |   ADV_Data[18] Encrypted  |   JSON[5]
Byte 24 |   AD2 Data 19 |   ADV_Data[19] Encrypted  |   JSON[6]
Byte 25 |   AD2 Data 20 |   ADV_Data[20] Encrypted  |   JSON[7]
Byte 26 |   AD2 Data 21 |   ADV_Data[21] Encrypted  |   JSON[8]
Byte 27 |   AD2 Data 22 |   ADV_Data[22] Encrypted  |   JSON[9]
Byte 28 |   AD2 Data 23 |   ADV_Data[23] Encrypted  |   JSON[10]
Byte 29 |   AD2 Data 24 |   ADV_Data[24] Encrypted  |   JSON[11]
Byte 30 |   AD2 Data 25 |   ADV_Data[25] Encrypted  |   JSON[12]

***************************************************/


static uint8_t key[16] = {0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4};
//26 bytes adv data
static uint8_t encrypted[26] = {0x0,0x0,0x0,0x1,0x1,0x1,0x2,0x2,0x2,0x3,0x3,0x3,0x4,0x4,0x4,0x5,0x5,0x5,0x6,0x6,0x6,0x7,0x7,0x7,0x8,0x8};   /* Example of hex data */
//static uint8_t key_buf[16] = {0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4};
static uint8_t key_buf[16] = {0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x1, 0x2};
static uint8_t src_buf[16] = {0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4};
static uint8_t des_buf[16] = {0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4,0x1,0x2,0x3,0x4};

uint8_t Xmit_Cnt = 1;
uint8_t Recent_Cnt = 0;
const uint8_t Recent_max = 50;

/* **** NOT USED **** */
//16byte UUID loading happens here
//Look at <GapAdvertisingData.h> for rest of definition
struct ApplicationData_t {
    //Byte 0:  AppID High Byte
    //Byte 1:  AppID Low Byte
    //Byte 2:  sensor High Word
    //Byte 3:
    //Byte 4:
    //Byte 5:  sensor Low Byte
    
    
    //app ID is 16 bit, (0xFEFE)
    uint16_t    applicationSpecificId; /* An ID used to identify temperature value in the manufacture specific AD data field */
    
    //TMP_nrf51::TempSensorValue_t tmpSensorValue;        /* this is a float (32-bit), user data */
} PACKED;



void debounce_Callback(void)
{
    Tic_Debounce.detach();
    Flag_Update_IO = true;  //start advertising
    /* Note that the buttonPressedCallback() executes in interrupt context, so it is safer to access
     * BLE device API from the main thread. */
    Recent_Cnt = 0;     //reset this to cause sensor shorten periodic update period
}


//ISR for I/O interrupt
void buttonPressedCallback(void)
{
    Tic_Debounce.attach(debounce_Callback, 3); //ok to attach multiple times, recent one wins
}

//ISR for I/O interrupt
void buttonReleasedCallback(void)
{
    
    Tic_Debounce.attach(debounce_Callback, 3);  
}


void stop_adv_Callback(void)
{
    //stops advertising after X seconds
    /* Note that the Callback() executes in interrupt context, so it is safer to do
     * heavy-weight sensor polling from the main thread (where we should be able to block safely, if needed). */
    Flag_Detach_Adv_Tic = true;

}

/* ****************************************
 * Decides what actions need to be performed on periodic basis
*******************************************/
void periodic_Callback(void)
{
    Flag_Update_IO = true;
    Flag_Periodic_Call = true;
}


/* ****************************************
 * No RTC available, tickers only have a 35 minute range.
 * So periodicity for spoof avoidance is set to 30 minutes
*******************************************/
void clock_reset_Callback(void)
{
#if MyDebugEnb
    device.printf("===== reset timer =====");
    device.printf("\r\n");
#endif
    Tmr_From_Birthday.reset();
};


void setupApplicationData(ApplicationData_t &appData)
{
    // two byte ID:  0xFEFE
    static const uint16_t APP_SPECIFIC_ID_TEST = 0xFEFE;        //2 byte application ID

    appData.applicationSpecificId = APP_SPECIFIC_ID_TEST;
}



/**
 * This function is called when the ble initialization process has failled
 */
void onBleInitError(BLE &ble, ble_error_t error)
{
    /* Initialization error handling should go here */
}



/**
 * Callback triggered when the ble initialization process has finished
 */
void bleInitComplete(BLE::InitializationCompleteCallbackContext *params)
{
    BLE&        ble   = params->ble;
    ble_error_t error = params->error;

    if (error != BLE_ERROR_NONE) {
        /* In case of error, forward the error handling to onBleInitError */
        onBleInitError(ble, error);
        return;
    }

    /* Ensure that it is the default instance of BLE */
    if(ble.getInstanceID() != BLE::DEFAULT_INSTANCE) {
        return;
    }
    
    /* Set device name characteristic data */
    ble.gap().setDeviceName((const uint8_t *) DEVICE_NAME);

    /* Setup advertising payload */
    //set modes "no EDR", "discoverable" for beacon type advertisements
    ble.gap().accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED | GapAdvertisingData::LE_GENERAL_DISCOVERABLE);
    

    //from GAP example
    /* Sacrifice 2B of 31B to AdvType overhead, rest goes to AdvData array you define */
    ble.gap().accumulateAdvertisingPayload(GapAdvertisingData::MANUFACTURER_SPECIFIC_DATA, AdvData, sizeof(AdvData));

    /* Setup advertising parameters:  not connectable */
    ble.gap().setAdvertisingType(GapAdvertisingParams::ADV_NON_CONNECTABLE_UNDIRECTED);
    ble.gap().setAdvertisingInterval(200);  //one advertisment every 300ms.  Self tickers, so you don't have to worry.

}


//not needed anymore
void my_analogin_init(void)
{
    
    NRF_ADC->CONFIG = (ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos) |
                      (ADC_CONFIG_INPSEL_SupplyOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) |
                      //(ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) |
                      (ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos) |
                      (ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos) |
                      //(ADC_CONFIG_PSEL_AnalogInput4 << ADC_CONFIG_PSEL_Pos) |
                      (ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos);
    NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Enabled;
}


/* ****************************************
 * Read battery voltage using bandgap reference
 * shunt Vdd to ADC, thanks to Marcelo Salazar's notes here:
 * https://developer.mbed.org/users/MarceloSalazar/notebook/measuring-battery-voltage-with-nordic-nrf51x/
*******************************************/
uint16_t read_bat_volt(void)
{
    //10 bit resolution, route Vdd as analog input, set ADC ref to VBG band gap
    //disable analog pin select "PSEL" because we're using Vdd as analog input
    //no external voltage reference
    NRF_ADC->CONFIG = (ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos) |
                      (ADC_CONFIG_INPSEL_SupplyOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) |
                      //(ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) |
                      (ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos) |
                      (ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos) |
                      //(ADC_CONFIG_PSEL_AnalogInput4 << ADC_CONFIG_PSEL_Pos) |
                      (ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos);

    //NRF_ADC->CONFIG     &= ~ADC_CONFIG_PSEL_Msk;
    //NRF_ADC->CONFIG     |= ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos;
    NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Enabled;
    NRF_ADC->TASKS_START = 1;
    
    
    //while loop doesn't actually loop until reading comlete, use a wait.
    while (((NRF_ADC->BUSY & ADC_BUSY_BUSY_Msk) >> ADC_BUSY_BUSY_Pos) == ADC_BUSY_BUSY_Busy) {};
    wait_ms(1);

    //save off RESULT before disabling.
    //uint16_t myresult = (uint16_t)NRF_ADC->RESULT;
    
    //disable ADC to lower bat consumption
    NRF_ADC->TASKS_STOP = 1;
    //NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Disabled;    //disable to shutdown ADC & lower bat consumption
    
    return (uint16_t)NRF_ADC->RESULT; // 10 bit
    //return myresult;
}  //end read_bat_volt



/* ****************************************
 * Read battery voltage using bandgap reference
 * shunt analog pin to ADC, from API here
 * https://developer.mbed.org/users/mbed_official/code/mbed-src/file/cb4253f91ada/targets/hal/TARGET_NORDIC/TARGET_NRF51822/analogin_api.c
*******************************************/
uint16_t read_ADC_pin(void)
{

    //10 bit resolution, route PSEL pin as 1/3 input sel,
    //set ADC ref to VBG band gap
    //set AnalogInput4 as input pin (this is P0.03)
    //no external voltage reference
    NRF_ADC->CONFIG = (ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos) |
                      //(ADC_CONFIG_INPSEL_SupplyOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) |
                      (ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) |
                      (ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos) |
                       //ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos) |
                      (ADC_CONFIG_PSEL_AnalogInput4 << ADC_CONFIG_PSEL_Pos) |
                      (ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos);
    //set pin select to AnalogInput4 = pin 7 = p0.03 = AIN4
    //NRF_ADC->CONFIG     &= ~ADC_CONFIG_PSEL_Msk;
    //NRF_ADC->CONFIG     |= ADC_CONFIG_PSEL_AnalogInput4 << ADC_CONFIG_PSEL_Pos;
    NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Enabled;
    NRF_ADC->TASKS_START = 1;
    
    
    //while loop doesn't actually loop until reading comlete, use a wait.
    while (((NRF_ADC->BUSY & ADC_BUSY_BUSY_Msk) >> ADC_BUSY_BUSY_Pos) == ADC_BUSY_BUSY_Busy) {};
    wait_ms(1);     //needed because busy while loop doesn't run.

    //save off RESULT before disabling.
    //uint16_t myresult = (uint16_t)NRF_ADC->RESULT;
    
    //disable ADC to lower bat consumption
    //NRF_ADC->TASKS_STOP = 1;
    //NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Disabled;    //disable to shutdown ADC & lower bat consumption
    
    return (uint16_t)NRF_ADC->RESULT; // 10 bit
    //return myresult;
}  //end read_ADC_pin


/* ****************************************
 * Pattern scheme indicating "one of ours"
 * generate first part of ADV data so that observer can recognize it as "one of ours".
 * use specific schema to decide how we're recognizing our sensor ADV
*******************************************/
void hash_first_section(uint8_t * dest, const uint8_t * mac_addr, const char * bat_volt_str)
{
    dest[0] = mac_addr[3];
    dest[1] = mac_addr[2];
    dest[2] = mac_addr[1];
    dest[3] = mac_addr[0];
    dest[4] = bat_volt_str[0];
    dest[5] = bat_volt_str[1];
    dest[6] = bat_volt_str[2];
    dest[7] = bat_volt_str[3];
    dest[8] = 0x10;
    dest[9] = 0x11;
    #if MyDebugEnb
        
        device.printf("hash array: ");
        for (int i=0; i<10; i++)
        {
            device.printf("%x ", dest[i]);
        }
        device.printf("\r\n");
    #endif
}


/* ****************************************
 * 
 * Main Loop
 * 
*******************************************/
int main(void)
{

    #if MyDebugEnb
        device.baud(9600);
        device.printf("started sensor node 36 ");
        device.printf("\r\n");
    #endif

    //pinHandShake = 0;
    //pinHandShake.mode(PullNone); //Expecting gateway to set pin high for flow control
    Tmr_From_Birthday.start();      //tracks # sec since birthday


    BLE &ble = BLE::Instance();
    ble.init(bleInitComplete);
    
    float bat_reading;  //hold battery voltage reading (Vbg/Vcc)
    
    my_analogin_init();//routes band-gap to analog input

    /* SpinWait for initialization to complete. This is necessary because the
     * BLE object is used in the main loop below. */
    while (ble.hasInitialized() == false) { /* spin loop */ }
    
    //every X seconds, sends period update, up to 1800 (30 minutes)
    Tic_Periodic.attach(periodic_Callback, Periodic_Update_Seconds);  //send updated I/O every x seconds
    Tic_Birthday.attach(clock_reset_Callback, Periodicity);  //clock algorithm periodicity


    ble.getAddress(0,mac_reverse);  //last byte of MAC (as shown on phone app) is at mac[0], not mac[6];
    #if MyDebugEnb
        device.printf("mac = ");
        for (int i=0; i<6; i++) //prints out MAC address in reverse order; opps.
        {
            device.printf("%x:", mac_reverse[i]);
        }
        device.printf("\r\n");
    #endif
    while (true) 
    {  //Main Loop

        uint16_t seconds_Old =(uint16_t)(Tmr_From_Birthday.read_ms()/1000); // 0-1800 seconds (30 minutes)

        #if MyDebugEnb
            device.printf("current time in seconds: %d \r\n", seconds_Old);
        #endif

        
        
        //used to increase sensor periodic output more frequently after window is opened
        if (Recent_Cnt <= Recent_max)
        {
            Recent_Cnt++;
        }
        if (Recent_Cnt < Recent_max)
        {
            Periodic_Update_Seconds = 5;
        }
        else
        {
            Periodic_Update_Seconds = 600;
        }

        
        
        //set both pins to pull-up, so they're not floating when we read state
        button1.mode(PullUp);
        button2.mode(PullUp);
        
        //expect either button1 or button2 is grounded, b/c using SPDT reed switch
        //the "common" pin on the reed switch should be on GND
        uint8_t button1_state = button1.read();
        uint8_t button2_state = button2.read();
        
        //disable pull up on pins that are grounded.
        if (button1_state == 0) 
        {
            button1.fall(NULL);     //disable interrupt
            button1.rise(NULL);     //disable interrupt
            button1.mode(PullNone); //float pin to save battery
        }
        else
        {
            button1.fall(buttonReleasedCallback);     //enable interrupt
            button1.rise(buttonReleasedCallback);     //enable interrupt
            button1.mode(PullUp); //pull up on pin to get interrupt
        }
        
        //disable pull up on pins that are grounded.
        if (button2_state == 0) 
        {
            button2.fall(NULL);     //disable interrupt
            button2.rise(NULL);     //disable interrupt
            button2.mode(PullNone); //float pin to save battery
        }
        else
        {
            button2.fall(buttonReleasedCallback);     //enable interrupt
            button2.rise(buttonReleasedCallback);     //enable interrupt
            button2.mode(PullUp); //pull up on pin to get interrupt
        }
        

        
        if (Flag_Update_IO) {
            
            //pinHandShake = 1; //enable distance sensor
            //wait_ms(500);   //let sensor run
            /* Do blocking calls or whatever hardware-specific action is
             * necessary to poll the sensor. */

            //call attach again on periodic update to reset ticker
            //next periodic updates happens Perioidc_Update_Seconds after I/O events
            Tic_Periodic.attach(periodic_Callback, Periodic_Update_Seconds);   
            Xmit_Cnt++; //increment transmit counter when updating I/O
            
            
            //read and convert battery voltage
            bat_reading = (float)read_bat_volt();    
            bat_reading = (bat_reading * 3.6) / 1024.0;
            #if MyDebugEnb
            device.printf("bat reading: %f \r\n", bat_reading);
            #endif
            //write battery voltage
            uint8_t total_chars;
            memset(&bat_volt_char[0], 0, sizeof(bat_volt_char));      //clear out buffer
            //convert battery voltage float value to string reprsentation to 2 decimal places, and save the size of string.
            total_chars = sprintf (bat_volt_char, "%.2f", bat_reading);
            
            
            //read and convert analog voltage.  Comment out this section if note needed, saves some battery
            NRF_ADC->TASKS_STOP = 1;
            float analogreading;
            analogreading = (float)read_ADC_pin();
            analogreading = (analogreading * 3.6) / 1024.0;
            #if MyDebugEnb
            device.printf("separate analog reading: %.02f \r\n", analogreading);
            #endif
            
            //disable ADC to save power
            NRF_ADC->TASKS_STOP = 1;
            NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Disabled;    //disable to shutdown ADC & lower bat consumption

            //read distance using VL6180 
            float sensor_reading = rf;
            uint8_t total_chars_sensor;
            memset(&sensor_char[0], 0, sizeof(sensor_char));      //clear out buffer
            total_chars_sensor = sprintf (sensor_char, "%.2f", sensor_reading);
            
            //pinHandShake = 0; //enable distance sensor

            #if MyDebugEnb
            device.printf("char buff: %c%c%c%c \r\n", bat_volt_char[0], bat_volt_char[1], bat_volt_char[2], bat_volt_char[3]);
            device.printf("num chars: %d \r\n", total_chars);
            #endif


            //Generate "First Section" for ADV_Data so gateway will recognize our advertisement pattern
            hash_first_section(Adv_First_Section, mac_reverse, bat_volt_char);


            /* ****************************************
             * start writing out ADVData array
             * todo: this is easy to write but hard to read.  Maybe make it easy to read and hard to write?
             ******************************************/
            memset(&AdvData[0], 0, sizeof(AdvData));
            uint8_t JSON_loc=0; //AdvData[0]

            AdvData[0] = Adv_First_Section[0];          //"our device" flag, MAC[3]
            JSON_loc++; //JSON_loc == 1
            AdvData[1] = Adv_First_Section[1];          //"out device" flag, MAC[2]...
            JSON_loc++; //JSON_loc == 2
            AdvData[2] = Adv_First_Section[2];
            JSON_loc++; //JSON_loc == 3
            AdvData[3] = Adv_First_Section[3];
            JSON_loc++;  //JSON_loc == 4
            AdvData[4] = Adv_First_Section[4];
            JSON_loc++;  //JSON_loc == 5
            AdvData[5] = Adv_First_Section[5];
            JSON_loc++;  //JSON_loc == 6
            AdvData[6] = Adv_First_Section[6];
            JSON_loc++;
            AdvData[7] = Adv_First_Section[7];
            JSON_loc++;
            AdvData[8] = Adv_First_Section[8];
            JSON_loc++;
            AdvData[9] = Adv_First_Section[9];
            JSON_loc++;

            #if MyDebugEnb
                device.printf("ADV first 10 array: ");
                for (int i=0; i<10; i++)
                {
                    device.printf("%x ", AdvData[i]);
                }
                device.printf("\r\n");
            #endif


            JSON_loc = 10;
            //Start of encrypted user data
            
            //[10] and [11] hold 2 bytes for how many seconds since birthday, little endian
            AdvData[10] = seconds_Old & 0xFF;
            JSON_loc++;
            AdvData[11] = (seconds_Old >> 8) & 0xFF;
            JSON_loc++;
            
            AdvData[12] = Xmit_Cnt;
            JSON_loc++;
            
            //start of jason data
            //"mag":
            JSON_loc = 13;  //hardcode should be 13
            AdvData[JSON_loc] = 0x22;       //ADV_Data[13] = "
            JSON_loc++; //14
            
            AdvData[JSON_loc] = 0x44;       //ADV_Data[14] = D
            JSON_loc++; //15
            
            AdvData[JSON_loc] = 0x49;       //ADV_Data[15] = I
            JSON_loc++; //16
            
            AdvData[JSON_loc] = 0x53;       //ADV_Data[16] = S
            JSON_loc++; //17
            
            //for periodic calls, we want to add an extra mqtt level "p", using "/p"
            //to delineate between MQTT publishes from real world I/O interrupts vs timer interrupts
            if (Flag_Periodic_Call)
            {
                AdvData[JSON_loc] = 0x2f;       // ADV_Data[17] = /
                JSON_loc++;  //18
                AdvData[JSON_loc] = 0x70;       // ADV_Data[18] =p
                JSON_loc++;  //19
            }
            
            AdvData[JSON_loc] = 0x22;       //ADV_Data[17 or 19] = "   
            JSON_loc++; //20

            AdvData[JSON_loc] = 0x3a;       //ADV_Data[18 or 20] = :
            JSON_loc++; //21
            
            //convert magnet variable to string, for magnet sensor, this is easy
            //since we only have 1 or 0, but this also works for analog values
            /*
            memset(&buffer[0], 0, sizeof(buffer));      //clear out buffer
            total_chars = sprintf (buffer, "%d", magnet_near);    //returns total number of characters, which is 1 character.
            for (int i=0; i < total_chars; i++)
            {
                AdvData[JSON_loc] = buffer[i];
                JSON_loc++; //23
            } //JSON_loc left at location of next character
            */
            
            //memset(&buffer[0], 0, sizeof(buffer));      //clear out buffer
            for (int i=0; i < total_chars_sensor; i++)
            {
                AdvData[JSON_loc] = sensor_char[i];
                JSON_loc++;
            } //JSON_loc left at location of next character
            
                        
            //AdvData[JSON_loc] = 0x0;    //since AdvData was cleared to start with, we don't need to null term

            ApplicationData_t appData;
            setupApplicationData(appData);
            
            /*********************
             * start encrypting last 16 bytes of ADV_Data
            *********************/
            for (int i=0; i<16; i++)
            {
                src_buf[i] = AdvData[i+10]; //start of encrypted section is at AdvData[10]
            }
            nrf_ecb_init();
            nrf_ecb_set_key(key_buf);
            bool successful_ecb = nrf_ecb_crypt(des_buf, src_buf);
            #if MyDebugEnb
                device.printf("success ecb = %d \r\n", successful_ecb);
                device.printf("src_buf: %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x \r\n", src_buf[0], src_buf[1], src_buf[2], src_buf[3], src_buf[4], src_buf[5], src_buf[6], src_buf[7], src_buf[8], src_buf[9], src_buf[10], src_buf[11], src_buf[12], src_buf[13], src_buf[14], src_buf[15]);
                device.printf("des_buf: %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x %x \r\n", des_buf[0], des_buf[1], des_buf[2], des_buf[3], des_buf[4], des_buf[5], des_buf[6], des_buf[7], des_buf[8], des_buf[9], des_buf[10], des_buf[11], des_buf[12], des_buf[13], des_buf[14], des_buf[15]);
            #endif
            for (int i=0; i<16; i++)  //replace last 16 bytes with encrypted 16 bytes
            {
                AdvData[i+10] = des_buf[i];
            }
            
            //set payload for advertisement to our custom manufactured data.  First 5 bytes is BLE standard, last 26 bytes is our array
            //ble.gap().updateAdvertisingPayload(GapAdvertisingData::MANUFACTURER_SPECIFIC_DATA, (uint8_t *) &appData, sizeof(ApplicationData_t));
            ble.gap().accumulateAdvertisingPayload(GapAdvertisingData::MANUFACTURER_SPECIFIC_DATA, AdvData, sizeof(AdvData));
            
            Flag_Update_IO = false;
            Flag_Periodic_Call = false;
            
            ble.gap().startAdvertising();
            Tic_Stop_Adv.attach(stop_adv_Callback, 4); /* trigger turn off advertisement after X seconds */
        
        }//end Flag_Update_IO
        
        
        if (Flag_Detach_Adv_Tic == true)    //ticker callback flag to stop advertising
        {
            ble.gap().stopAdvertising();    //may be safer to execute BLE operations in main
            Tic_Stop_Adv.detach();
            Flag_Detach_Adv_Tic = false;
        }

        
        ble.waitForEvent(); //sleeps until interrupt form ticker or I/O
    }//end forever while
}//end main