Aietes

//print uint64_t 4 bits at a time, single HEX digit
uint64_t chipid = ESP.getEfuseMac();
for (size_t i = 0; i < 16; i++)
{
  byte byte1 = chipid >> 4*i & 0x0000000F;
  Serial.printf("%X ", byte1);
}
// 0 3 E A 4 A 0 4 A E 0 E 0 0 0 0

//print uint64_t 4 bits at a time, in pairs of 8 bits, single HEX digit

Aietes

#include <nvs.h>
#include <nvs_flash.h>
/**
 * Testing dedicated NVS partition access
 * 
 * Used partition table
 * # Name,     Type,   SubType,    Offset,     Size,   Flags
 * nvs,        data,	nvs,	    0x9000,	    0x3000	
 * void,	    data,	nvs,	    0xC000,	    0x2000	
 * nvs_key,	data,	nvs_keys,	0xE000,	    0x1000