extern "C" {
  #include "user_interface.h"
}

byte complete_rtc_mem[512];

void hexDump(char *desc, void *addr, int len) {
    int i;
    unsigned char buff[17];
    unsigned char *pc = (unsigned char*)addr;

    // Output description if given.
    if (desc != NULL)
        Serial.printf ("%s:\n", desc);

    if (len == 0) {
        Serial.printf("  ZERO LENGTH\n");
        return;
    }
    if (len < 0) {
        Serial.printf("  NEGATIVE LENGTH: %i\n",len);
        return;
    }

    // Process every byte in the data.
    for (i = 0; i < len; i++) {
        // Multiple of 16 means new line (with line offset).

        if ((i % 16) == 0) {
            // Just don't print ASCII for the zeroth line.
            if (i != 0)
                Serial.printf ("  %s\n", buff);

            // Output the offset.
            Serial.printf ("  %04x ", i);
        }

        // Now the hex code for the specific character.
        Serial.printf (" %02x", pc[i]);

        // And store a printable ASCII character for later.
        if ((pc[i] < 0x20) || (pc[i] > 0x7e))
            buff[i % 16] = '.';
        else
            buff[i % 16] = pc[i];
        buff[(i % 16) + 1] = '\0';
    }

    // Pad out last line if not exactly 16 characters.
    while ((i % 16) != 0) {
        Serial.printf ("   ");
        i++;
    }

    // And print the final ASCII bit.
    Serial.printf ("  %s\n", buff);
}



void setup() {

  //setup serial
  Serial.begin(115200);
  Serial.printf("\n\nsystem start - dump RTC\n");

  //read memory
  system_rtc_mem_read(0, complete_rtc_mem, 512);

  //dump memory to console
  hexDump ("rtcmem", &complete_rtc_mem, sizeof(complete_rtc_mem));

  //modify memory
  for(int i=0;i<512;i++){
    complete_rtc_mem[i]++;  
  }

  //write back to memory
  system_rtc_mem_write(0, complete_rtc_mem, 512);

  //deepsleep for 5 seconds (remember to connect RST and GPIO16)
  ESP.deepSleep(5*1000*1000, WAKE_RF_DISABLED);
}

void loop() {
  //never reach
}