File content as of revision 0:99404616b1d5:

/**
read data temperature,time from DS3221 and write it to 25LC1024
author: Danyal Awan, Johannes Bienert, Max Östermann
*/

#include "mbed.h"
#define ADDR 0x68 << 1 // DS3231 adress
#define MESSPUNKTE 100 //Anzahl der Messungen, die durchgeführt werden sollen.
#define ADDRESSINCREASE 5// Anzahl der Adressen (25LC1024), die erhöht werden müssen.
                        //5 Werte pro Messung werden gespeichert.
#define PRESSED 0 // wenn Userbutton gedrückt
#define DELAY_IN_MS 100 // Millisekunden, die zwischen den Messungen gewartet werden soll.

Serial pc(SERIAL_TX, SERIAL_RX); // Serielle Schnittstelle 
DigitalIn userButton(BUTTON1, PullUp); // Onboard Button 
I2C i2c(I2C_SDA , I2C_SCL); 
SPI spi(D11, D12, D13); // mosi, miso, sclk
DigitalOut cs(D10);
//DigitalOut out(D9);
AnalogIn input(A0); // Input for temperature data
int32_t counter;


// DS3231 must bet set in 24h mode!!!
// get time in hours from DS3231 via I2C
// @return hours 8_bit integer
int8_t getHours() {
  
  char reader[1]; 
  char cmd[1];    
  cmd[0]=0x02;  // register for hours
  wait_ms(1);
  i2c.write(ADDR, cmd, 1);
  i2c.read(ADDR, reader, 1);
  int8_t stunden = reader[0];
  stunden = stunden & 0x3F;  
  return stunden;    
    
}

// get time in minutes from DS3231 via I2C
// @return minutes 8_bit integer
int8_t getMinutes(){
  
  char reader[1];
  char cmd[1]; 
  cmd[0]=0x01; //register for minutes
  i2c.write(ADDR, cmd, 1); 
  i2c.read(ADDR, reader, 1);
  wait_ms(1);
  int8_t minuten = reader[0];
  return minuten;
  
} 

// get temperature from DS3231 via I2C
// @return temperature 8_bit integer
int8_t getTemp(){
     
    int8_t temp = 0; 
    char reader[1];
    char cmd[1];   
    cmd[0]=0x11; // register for temperature in front of comma
    i2c.write(ADDR, cmd, 1);
    i2c.read(ADDR, reader, 1);
    wait_ms(1);
    temp = reader[0];
    return temp;
}

// get analog input from phototransistor
// @return input voltage 16_bit integer
int16_t getInput(){  

    uint16_t inputWert = 0; 
    inputWert = input.read_u16();
    return inputWert;    
}

// write data to 25LC1024 via SPI
// @param Stunden
// @param Minuten
// @param temperature
// @param Voltage - 16_bit
// @param 24_bit register adress
void saveData(int8_t dataHour,int32_t adress,int8_t dataMinutes,
                                   int8_t dataTemp,int16_t light){
                                       
    char addr1, addr2, addr3,msb2,lsb2; // 1 Byte adress holder
    
    //  split 24_bit adress in 3 8_bit adresses
    addr1=(adress & 0xFF0000)>>16;
    addr2= (adress & 0x00FF00)>>8;
    addr3= (adress & 0x0000FF);
    
    //split 16_bit integer in two 8_bit values
    msb2=(light & 0xFF00)>>8;
    lsb2=(light & 0x00FF);
        
    cs = 0; 
    spi.write(0x06); //WREN, Write on
    cs = 1;
    wait_ms(1);
    cs = 0;
    spi.write(0x02); //Write Instruction
    spi.write(addr1); //      -
    spi.write(addr2); // send 24_bit adress devided up by 3 8_bit integers
    spi.write(addr3); //      -
    spi.write(dataTemp);  // send data
    spi.write(dataHour);
    spi.write(dataMinutes);
    spi.write(msb2);
    spi.write(lsb2);
    cs=1; 
    wait_ms(6);
    cs = 0; 
    spi.write(0x04); //WRDI, Write off
    cs = 1;

}
// read all data from 25LC1024 via SPI
// send all data in own arrays
// print all data on screen
//@param number of all data
void readOutData(int32_t leng) {
      char buffer[leng];
      char minuten[MESSPUNKTE];
      char stunden[MESSPUNKTE];
      char temp[MESSPUNKTE];
      char light1[MESSPUNKTE];
      char light2[MESSPUNKTE];
       // Chip must be deselected    
      cs = 0;
      spi.write(0x03); // read instruction
      spi.write(0x00); //     --
      spi.write(0x00); // 24_bit adress
      spi.write(0x01); //     --
      for (int i = 0;i<leng;i++) {
        buffer[i]=spi.write(0x00);  // send all data in buffer[]
        }
      cs = 1;  
      wait_ms(1); 
      int x = 0;   
      // now send all data in seperated array´s
      for (int i = 0;i<leng;i=i+ADDRESSINCREASE) { 
          //pc.printf("%d : %x\n",x,buffer[i]);
          temp[x] = buffer[i];
          x++;
          }
          x=0;
          wait_ms(1);
      for (int i = 1;i<leng;i=i+ADDRESSINCREASE) {
         // pc.printf("%d : %x\n",x,buffer[i]);
          stunden[x] = buffer[i];
          x++;
          }
          x=0;
          wait_ms(1);
      for (int i = 2;i<leng;i=i+ADDRESSINCREASE) {
          //pc.printf("%d : %x\n",x,buffer[i]);
          minuten[x] = buffer[i];
          x++;
          }
          x=0;
          wait_ms(1);
      for (int i = 3;i<leng;i=i+ADDRESSINCREASE) {
         // pc.printf("%d : %x\n",x,buffer[i]);
          light1[x] = buffer[i];
          x++;
          }
          wait_ms(1);
          x=0;
      for (int i = 4;i<leng;i=i+ADDRESSINCREASE) {
         // pc.printf("%d : %x\n",x,buffer[i]);
          light2[x] = buffer[i];
          x++;
          }
      // print all messures. step by step
      for (int i = 0;i<counter;i++) {
          pc.printf("Messung: %d Temperatur: %d Uhrzeit: %x:%x Voltage:%x%x \n",i+1,temp[i],stunden[i],
          minuten[i],light1[i],light2[i]);
          }         
}

// if userbutton pressed programm ends and print all messures
// if userbutton is not pressed programm waits the delaytime till to the next messure.
// every 10 ms button query
//@param delay time in ms
//@return 0 or 1. 0 ends the programm, 1 continues
int8_t delayOrEnd(int32_t delay){
int32_t x=0;
int8_t y = 1;
while((x<delay/10) && y){
    if(userButton == PRESSED){
        y=0;
        }
    else{
        wait_ms(10);
        }
    x++;
}
return y;
} 
   
      
int main(){

 pc.printf("Press any key on the keyboard to start the program\n\r");
 pc.putc(pc.getc()); //echo keyboard input, blocking wait
 pc.printf(" was pressed\n\r");
 for (int32_t i=0;i<=5;i++){
 pc.printf("***\n\r"); //Generate some new lines
 }
 pc.printf("Messung wird gestartet.\n");
 pc.printf("Anzahl der vorrausichtlichen Messungen: %d.\n",MESSPUNKTE);
 pc.printf("Messabstaende in Millisekunden: %d.\n",DELAY_IN_MS);
 pc.printf("Userbutton druecken, um Messung vorlaeufig zu beenden.\n");

 cs = 1;
 // Setup the spi for 8 bit data, high steady state clock,
 // second edge capture, with a 1MHz clock rate
 spi.format(8,0);
 spi.frequency(100000);
 int32_t adress =0x01; // starting register adress
 
 //int x =0;
 int k = 1;
 counter = 0;
 while(counter<MESSPUNKTE && k){
          
        saveData(getHours(),adress,getMinutes(),getTemp(),getInput());
        wait_ms(1);
       
      adress = adress + ADDRESSINCREASE;   // erhöhe Speicheradresse um 5 
      counter++;
      pc.printf("Messung ausgefuehrt: %d\n",counter);
      k = delayOrEnd(DELAY_IN_MS);
      }
pc.printf("\n");
pc.printf("Messung beendet \n");
pc.printf("*************************************************\n");
readOutData(MESSPUNKTE*ADDRESSINCREASE); // MESSPUNKTE*ADDRESSINCREASE = Anzahl aller Daten.
  

}