ESP32 Bluetooth LE Secure Server for multi clients (ft. PassKey)

ESP32_TTGO/BLE_Secure_Server/BLE_Secure_Server.ino

@@ -0,0 +1,253 @@
+#include <Pangodream_18650_CL.h>
+#include "SPIFFS.h" 
+#include <TFT_eSPI.h>
+#include <TJpg_Decoder.h>
+#include "Free_Fonts.h"
+#include <BLEDevice.h>
+#include <BLEServer.h>
+#include <BLEUtils.h>
+
+#define ICON_WIDTH 70
+#define ICON_HEIGHT 36
+#define STATUS_HEIGHT_BAR ICON_HEIGHT
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
+#define ICON_POS_X (tft.width() - ICON_WIDTH)
+#define MIN_USB_VOL 4.9
+#define ADC_PIN 34
+#define CONV_FACTOR 1.8
+#define READS 20
+
+Pangodream_18650_CL BL(ADC_PIN, CONV_FACTOR, READS);
+char *batteryImages[] = {"/battery_01.jpg", "/battery_02.jpg", "/battery_03.jpg", "/battery_04.jpg", "/battery_05.jpg"};
+
+BLEServer* pServer = NULL;
+BLECharacteristic* pCharacteristic = NULL;
+#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
+#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"
+#define PASSKEY 999999
+
+TFT_eSPI tft = TFT_eSPI();
+
+SemaphoreHandle_t xGuiSemaphore;
+
+void setup() {
+  Serial.begin(115200);
+  pinoutInit();
+  SPIFFSInit();
+  displayInit();
+  bleInit();
+  xGuiSemaphore = xSemaphoreCreateMutex();
+  xTaskCreate(battery_info, "battery_info", 2048, NULL, 1, NULL);
+  delay(500);
+  xTaskCreate(ble_task, "ble_task", 2048, NULL, 2, NULL); 
+}
+
+void loop() {}
+
+/////////////////////
+//BLE Secure Server//
+/////////////////////
+
+class ServerCallback: public BLEServerCallbacks {
+    void onConnect(BLEServer* pServer) {
+      Serial.println(" - ServerCallback - onConnect");
+    };
+
+    void onDisconnect(BLEServer* pServer) {
+      Serial.println(" - ServerCallback - onDisconnect");
+    }
+};
+
+class SecurityCallback : public BLESecurityCallbacks {
+
+  uint32_t onPassKeyRequest(){
+    return 000000;
+  }
+
+  void onPassKeyNotify(uint32_t pass_key){}
+
+  bool onConfirmPIN(uint32_t pass_key){
+    vTaskDelay(5000);
+    return true;
+  }
+
+  bool onSecurityRequest(){
+    return true;
+  }
+
+  void onAuthenticationComplete(esp_ble_auth_cmpl_t cmpl){
+    if(cmpl.success){
+      Serial.println("   - SecurityCallback - Authentication Success");       
+    }else{
+      Serial.println("   - SecurityCallback - Authentication Failure*");
+      pServer->removePeerDevice(pServer->getConnId(), true);
+    }
+    BLEDevice::startAdvertising();
+  }
+};
+
+void bleSecurity(){
+  esp_ble_auth_req_t auth_req = ESP_LE_AUTH_REQ_SC_MITM_BOND;
+  esp_ble_io_cap_t iocap = ESP_IO_CAP_OUT;          
+  uint8_t key_size = 16;     
+  uint8_t init_key = ESP_BLE_ENC_KEY_MASK | ESP_BLE_ID_KEY_MASK;
+  uint8_t rsp_key = ESP_BLE_ENC_KEY_MASK | ESP_BLE_ID_KEY_MASK;
+  uint32_t passkey = PASSKEY;
+  uint8_t auth_option = ESP_BLE_ONLY_ACCEPT_SPECIFIED_AUTH_DISABLE;
+  esp_ble_gap_set_security_param(ESP_BLE_SM_SET_STATIC_PASSKEY, &passkey, sizeof(uint32_t));
+  esp_ble_gap_set_security_param(ESP_BLE_SM_AUTHEN_REQ_MODE, &auth_req, sizeof(uint8_t));
+  esp_ble_gap_set_security_param(ESP_BLE_SM_IOCAP_MODE, &iocap, sizeof(uint8_t));
+  esp_ble_gap_set_security_param(ESP_BLE_SM_MAX_KEY_SIZE, &key_size, sizeof(uint8_t));
+  esp_ble_gap_set_security_param(ESP_BLE_SM_ONLY_ACCEPT_SPECIFIED_SEC_AUTH, &auth_option, sizeof(uint8_t));
+  esp_ble_gap_set_security_param(ESP_BLE_SM_SET_INIT_KEY, &init_key, sizeof(uint8_t));
+  esp_ble_gap_set_security_param(ESP_BLE_SM_SET_RSP_KEY, &rsp_key, sizeof(uint8_t));
+}
+
+void bleInit(){
+  BLEDevice::init("BLE-Secure-Server");
+  BLEDevice::setEncryptionLevel(ESP_BLE_SEC_ENCRYPT);
+  BLEDevice::setSecurityCallbacks(new SecurityCallback());
+
+  pServer = BLEDevice::createServer();
+  pServer->setCallbacks(new ServerCallback());
+
+  BLEService *pService = pServer->createService(SERVICE_UUID);
+  pCharacteristic = pService->createCharacteristic(
+                      CHARACTERISTIC_UUID,
+                      BLECharacteristic::PROPERTY_READ   |
+                      BLECharacteristic::PROPERTY_WRITE  |
+                      BLECharacteristic::PROPERTY_NOTIFY 
+                    );
+
+  pCharacteristic->setAccessPermissions(ESP_GATT_PERM_READ_ENCRYPTED | ESP_GATT_PERM_WRITE_ENCRYPTED);
+  pService->start();
+
+  BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
+  pAdvertising->addServiceUUID(SERVICE_UUID);
+  pAdvertising->setScanResponse(false);
+  pAdvertising->setMinPreferred(0x0);
+  BLEDevice::startAdvertising();
+
+  bleSecurity();
+}
+
+static void ble_task(void *arg){
+  tft.setTextDatum(TL_DATUM);
+  tft.setFreeFont(FF22);
+  tft.setTextColor(TFT_SKYBLUE, TFT_BLACK);
+  tft.drawString("BLE", 0, 50, GFXFF);
+  tft.setFreeFont(FF21);
+  tft.setTextColor(TFT_RED, TFT_BLACK);
+  tft.drawString("Secure", 0, 75, GFXFF);
+  tft.setTextColor(TFT_SKYBLUE, TFT_BLACK);
+  tft.drawString("Server", 0, 95, GFXFF);
+  tft.drawString("Multi-Connect", 0, 115, GFXFF);
+  tft.setTextColor(TFT_RED, TFT_GREEN);
+  tft.drawString("PIN#: " + String(PASSKEY), 0, 135, GFXFF);
+  tft.setTextColor(TFT_WHITE, TFT_BLACK);
+  tft.drawString("Clients#", 0, 160, GFXFF);
+  
+  uint32_t value = 0;
+
+  while(1){
+    
+      xSemaphoreTake(xGuiSemaphore, portMAX_DELAY);
+      int connectedCount = pServer->getConnectedCount();
+       Serial.printf("connectedCount: %d\n", connectedCount);
+  
+      if (connectedCount >0) { 
+          pCharacteristic->setValue((uint8_t*)&value, 4);
+          pCharacteristic->notify();   
+      }
+      value++;
+
+      tft.fillRect(0, 180, tft.width(), tft.height() - 180, TFT_NAVY);
+      tft.setTextColor(TFT_GOLD, TFT_NAVY);
+      tft.setTextDatum(TC_DATUM); // Centre text on x,y position
+      tft.setFreeFont(FF24);
+      tft.drawString(String(connectedCount), tft.width()/2, 190, GFXFF);
+      TJpgDec.drawFsJpg(94, 40, value%2 == 0 ? "/bt_white.jpg" : "/bt_blue.jpg");
+      
+      xSemaphoreGive(xGuiSemaphore);
+      vTaskDelay(pdMS_TO_TICKS(1000));     
+  }
+}
+
+/////////////////////
+//Battery Indicator//
+/////////////////////
+
+void pinoutInit(){
+  pinMode(14, OUTPUT);
+}
+void SPIFFSInit(){
+  if (!SPIFFS.begin()) {
+    Serial.println("SPIFFS initialisation failed!");
+    while (1) yield(); // Stay here twiddling thumbs waiting
+  }
+  Serial.println("\r\nInitialisation done.");
+}
+
+void displayInit(){
+  tft.begin();
+  tft.setRotation(0);
+  tft.setTextColor(TFT_WHITE,TFT_BLACK); 
+  tft.fillScreen(TFT_BLACK);
+  tft.setSwapBytes(true);
+  tft.setTextFont(2);
+  TJpgDec.setJpgScale(1);
+  TJpgDec.setCallback(tft_output);
+}
+
+static void battery_info(void *arg){
+  while(1){  
+    digitalWrite(14, HIGH);
+    xSemaphoreTake(xGuiSemaphore, portMAX_DELAY);
+
+    if(BL.getBatteryVolts() >= MIN_USB_VOL){        
+      for(int i=0; i< ARRAY_SIZE(batteryImages); i++){
+        drawingBatteryIcon(batteryImages[i]);
+        drawingText("Chrg");
+        vTaskDelay(200 / portTICK_PERIOD_MS);
+      }
+    }else{
+      int imgNum = 0;
+      int batteryLevel = BL.getBatteryChargeLevel();
+      if(batteryLevel >=80){
+        imgNum = 3;
+      }else if(batteryLevel < 80 && batteryLevel >= 50 ){
+        imgNum = 2;
+      }else if(batteryLevel < 50 && batteryLevel >= 20 ){
+        imgNum = 1;
+      }else if(batteryLevel < 20 ){
+        imgNum = 0;
+      }  
+
+      drawingBatteryIcon(batteryImages[imgNum]);    
+      drawingText(String(batteryLevel) + "%");
+      vTaskDelay(1000 / portTICK_PERIOD_MS);
+    }
+    
+    xSemaphoreGive(xGuiSemaphore);
+    vTaskDelay(pdMS_TO_TICKS(1000)); 
+    digitalWrite(14, LOW);
+  }  
+}
+
+void drawingBatteryIcon(String filePath){
+   TJpgDec.drawFsJpg(ICON_POS_X, 0, filePath);
+}
+
+void drawingText(String text){
+  tft.fillRect(0, 0, ICON_POS_X, ICON_HEIGHT,TFT_BLACK);
+  tft.setTextDatum(5);
+  tft.setTextColor(TFT_WHITE, TFT_BLACK);
+  tft.drawString(text, ICON_POS_X-2, STATUS_HEIGHT_BAR/2, 4);
+}
+
+bool tft_output(int16_t x, int16_t y, uint16_t w, uint16_t h, uint16_t* bitmap)
+{
+  if ( y >= tft.height() ) return 0;
+  tft.pushImage(x, y, w, h, bitmap);
+  return 1;
+}

ESP32_TTGO/BLE_Secure_Server/Free_Fonts.h

@@ -0,0 +1,379 @@
+// Attach this header file to your sketch to use the GFX Free Fonts. You can write
+// sketches without it, but it makes referencing them easier.
+
+// This calls up ALL the fonts but they only get loaded if you actually
+// use them in your sketch.
+//
+// No changes are needed to this header file unless new fonts are added to the
+// library "Fonts/GFXFF" folder.
+//
+// To save a lot of typing long names, each font can easily be referenced in the
+// sketch in three ways, either with:
+//
+//    1. Font file name with the & in front such as &FreeSansBoldOblique24pt7b
+//       an example being:
+//
+//       tft.setFreeFont(&FreeSansBoldOblique24pt7b);
+//
+//    2. FF# where # is a number determined by looking at the list below
+//       an example being:
+//
+//       tft.setFreeFont(FF32);
+//
+//    3. An abbreviation of the file name. Look at the list below to see
+//       the abbreviations used, for example:
+//
+//       tft.setFreeFont(FSSBO24)
+//
+//       Where the letters mean:
+//       F = Free font
+//       M = Mono
+//      SS = Sans Serif (double S to distinguish is form serif fonts)
+//       S = Serif
+//       B = Bold
+//       O = Oblique (letter O not zero)
+//       I = Italic
+//       # =  point size, either 9, 12, 18 or 24
+//
+//  Setting the font to NULL will select the GLCD font:
+//
+//      tft.setFreeFont(NULL); // Set font to GLCD
+
+
+#ifdef LOAD_GFXFF // Only include the fonts if LOAD_GFXFF is defined in User_Setup.h
+
+// Use these when printing or drawing text in GLCD and high rendering speed fonts
+// Call up the font using tft.setTextFont()
+#define GFXFF 1
+#define GLCD  0
+#define FONT2 2
+#define FONT4 4
+#define FONT6 6
+#define FONT7 7
+#define FONT8 8
+
+// Use the following when calling tft.setFreeFont()
+//
+// Reserved for GLCD font  // FF0
+//
+
+#define TT1 &TomThumb
+
+#define FM9 &FreeMono9pt7b
+#define FM12 &FreeMono12pt7b
+#define FM18 &FreeMono18pt7b
+#define FM24 &FreeMono24pt7b
+
+#define FMB9 &FreeMonoBold9pt7b
+#define FMB12 &FreeMonoBold12pt7b
+#define FMB18 &FreeMonoBold18pt7b
+#define FMB24 &FreeMonoBold24pt7b
+
+#define FMO9 &FreeMonoOblique9pt7b
+#define FMO12 &FreeMonoOblique12pt7b
+#define FMO18 &FreeMonoOblique18pt7b
+#define FMO24 &FreeMonoOblique24pt7b
+
+#define FMBO9 &FreeMonoBoldOblique9pt7b
+#define FMBO12 &FreeMonoBoldOblique12pt7b
+#define FMBO18 &FreeMonoBoldOblique18pt7b
+#define FMBO24 &FreeMonoBoldOblique24pt7b
+
+#define FSS9 &FreeSans9pt7b
+#define FSS12 &FreeSans12pt7b
+#define FSS18 &FreeSans18pt7b
+#define FSS24 &FreeSans24pt7b
+
+#define FSSB9 &FreeSansBold9pt7b
+#define FSSB12 &FreeSansBold12pt7b
+#define FSSB18 &FreeSansBold18pt7b
+#define FSSB24 &FreeSansBold24pt7b
+
+#define FSSO9 &FreeSansOblique9pt7b
+#define FSSO12 &FreeSansOblique12pt7b
+#define FSSO18 &FreeSansOblique18pt7b
+#define FSSO24 &FreeSansOblique24pt7b
+
+#define FSSBO9 &FreeSansBoldOblique9pt7b
+#define FSSBO12 &FreeSansBoldOblique12pt7b
+#define FSSBO18 &FreeSansBoldOblique18pt7b
+#define FSSBO24 &FreeSansBoldOblique24pt7b
+
+#define FS9 &FreeSerif9pt7b
+#define FS12 &FreeSerif12pt7b
+#define FS18 &FreeSerif18pt7b
+#define FS24 &FreeSerif24pt7b
+
+#define FSI9 &FreeSerifItalic9pt7b
+#define FSI12 &FreeSerifItalic12pt7b
+#define FSI19 &FreeSerifItalic18pt7b
+#define FSI24 &FreeSerifItalic24pt7b
+
+#define FSB9 &FreeSerifBold9pt7b
+#define FSB12 &FreeSerifBold12pt7b
+#define FSB18 &FreeSerifBold18pt7b
+#define FSB24 &FreeSerifBold24pt7b
+
+#define FSBI9 &FreeSerifBoldItalic9pt7b
+#define FSBI12 &FreeSerifBoldItalic12pt7b
+#define FSBI18 &FreeSerifBoldItalic18pt7b
+#define FSBI24 &FreeSerifBoldItalic24pt7b
+
+#define FF0 NULL //ff0 reserved for GLCD
+#define FF1 &FreeMono9pt7b
+#define FF2 &FreeMono12pt7b
+#define FF3 &FreeMono18pt7b
+#define FF4 &FreeMono24pt7b
+
+#define FF5 &FreeMonoBold9pt7b
+#define FF6 &FreeMonoBold12pt7b
+#define FF7 &FreeMonoBold18pt7b
+#define FF8 &FreeMonoBold24pt7b
+
+#define FF9 &FreeMonoOblique9pt7b
+#define FF10 &FreeMonoOblique12pt7b
+#define FF11 &FreeMonoOblique18pt7b
+#define FF12 &FreeMonoOblique24pt7b
+
+#define FF13 &FreeMonoBoldOblique9pt7b
+#define FF14 &FreeMonoBoldOblique12pt7b
+#define FF15 &FreeMonoBoldOblique18pt7b
+#define FF16 &FreeMonoBoldOblique24pt7b
+
+#define FF17 &FreeSans9pt7b
+#define FF18 &FreeSans12pt7b
+#define FF19 &FreeSans18pt7b
+#define FF20 &FreeSans24pt7b
+
+#define FF21 &FreeSansBold9pt7b
+#define FF22 &FreeSansBold12pt7b
+#define FF23 &FreeSansBold18pt7b
+#define FF24 &FreeSansBold24pt7b
+
+#define FF25 &FreeSansOblique9pt7b
+#define FF26 &FreeSansOblique12pt7b
+#define FF27 &FreeSansOblique18pt7b
+#define FF28 &FreeSansOblique24pt7b
+
+#define FF29 &FreeSansBoldOblique9pt7b
+#define FF30 &FreeSansBoldOblique12pt7b
+#define FF31 &FreeSansBoldOblique18pt7b
+#define FF32 &FreeSansBoldOblique24pt7b
+
+#define FF33 &FreeSerif9pt7b
+#define FF34 &FreeSerif12pt7b
+#define FF35 &FreeSerif18pt7b
+#define FF36 &FreeSerif24pt7b
+
+#define FF37 &FreeSerifItalic9pt7b
+#define FF38 &FreeSerifItalic12pt7b
+#define FF39 &FreeSerifItalic18pt7b
+#define FF40 &FreeSerifItalic24pt7b
+
+#define FF41 &FreeSerifBold9pt7b
+#define FF42 &FreeSerifBold12pt7b
+#define FF43 &FreeSerifBold18pt7b
+#define FF44 &FreeSerifBold24pt7b
+
+#define FF45 &FreeSerifBoldItalic9pt7b
+#define FF46 &FreeSerifBoldItalic12pt7b
+#define FF47 &FreeSerifBoldItalic18pt7b
+#define FF48 &FreeSerifBoldItalic24pt7b
+
+// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
+// Now we define "s"tring versions for easy printing of the font name so:
+//   tft.println(sFF5);
+// will print
+//   Mono bold 9
+// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
+
+#define sFF0 "GLCD"
+#define sTT1 "Tom Thumb"
+#define sFF1 "Mono 9"
+#define sFF2 "Mono 12"
+#define sFF3 "Mono 18"
+#define sFF4 "Mono 24"
+
+#define sFF5 "Mono bold 9"
+#define sFF6 "Mono bold 12"
+#define sFF7 "Mono bold 18"
+#define sFF8 "Mono bold 24"
+
+#define sFF9 "Mono oblique 9"
+#define sFF10 "Mono oblique 12"
+#define sFF11 "Mono oblique 18"
+#define sFF12 "Mono oblique 24"
+
+#define sFF13 "Mono bold oblique 9"
+#define sFF14 "Mono bold oblique 12"
+#define sFF15 "Mono bold oblique 18"
+#define sFF16 "Mono bold oblique 24" // Full text line is too big for 480 pixel wide screen
+
+#define sFF17 "Sans 9"
+#define sFF18 "Sans 12"
+#define sFF19 "Sans 18"
+#define sFF20 "Sans 24"
+
+#define sFF21 "Sans bold 9"
+#define sFF22 "Sans bold 12"
+#define sFF23 "Sans bold 18"
+#define sFF24 "Sans bold 24"
+
+#define sFF25 "Sans oblique 9"
+#define sFF26 "Sans oblique 12"
+#define sFF27 "Sans oblique 18"
+#define sFF28 "Sans oblique 24"
+
+#define sFF29 "Sans bold oblique 9"
+#define sFF30 "Sans bold oblique 12"
+#define sFF31 "Sans bold oblique 18"
+#define sFF32 "Sans bold oblique 24"
+
+#define sFF33 "Serif 9"
+#define sFF34 "Serif 12"
+#define sFF35 "Serif 18"
+#define sFF36 "Serif 24"
+
+#define sFF37 "Serif italic 9"
+#define sFF38 "Serif italic 12"
+#define sFF39 "Serif italic 18"
+#define sFF40 "Serif italic 24"
+
+#define sFF41 "Serif bold 9"
+#define sFF42 "Serif bold 12"
+#define sFF43 "Serif bold 18"
+#define sFF44 "Serif bold 24"
+
+#define sFF45 "Serif bold italic 9"
+#define sFF46 "Serif bold italic 12"
+#define sFF47 "Serif bold italic 18"
+#define sFF48 "Serif bold italic 24"
+
+#else // LOAD_GFXFF not defined so setup defaults to prevent error messages
+
+// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
+// Free fonts are not loaded in User_Setup.h so we must define all as font 1
+// to prevent compile error messages
+// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
+
+#define GFXFF 1
+#define GLCD  1
+#define FONT2 2
+#define FONT4 4
+#define FONT6 6
+#define FONT7 7
+#define FONT8 8
+
+#define TT1 1
+
+#define FF0 1
+#define FF1 1
+#define FF2 1
+#define FF3 1
+#define FF4 1
+#define FF5 1
+#define FF6 1
+#define FF7 1
+#define FF8 1
+#define FF9 1
+#define FF10 1
+#define FF11 1
+#define FF12 1
+#define FF13 1
+#define FF14 1
+#define FF15 1
+#define FF16 1
+#define FF17 1
+#define FF18 1
+#define FF19 1
+#define FF20 1
+#define FF21 1
+#define FF22 1
+#define FF23 1
+#define FF24 1
+#define FF25 1
+#define FF26 1
+#define FF27 1
+#define FF28 1
+#define FF29 1
+#define FF30 1
+#define FF31 1
+#define FF32 1
+#define FF33 1
+#define FF34 1
+#define FF35 1
+#define FF36 1
+#define FF37 1
+#define FF38 1
+#define FF39 1
+#define FF40 1
+#define FF41 1
+#define FF42 1
+#define FF43 1
+#define FF44 1
+#define FF45 1
+#define FF46 1
+#define FF47 1
+#define FF48 1
+
+#define FM9  1
+#define FM12 1
+#define FM18 1
+#define FM24 1
+
+#define FMB9  1
+#define FMB12 1
+#define FMB18 1
+#define FMB24 1
+
+#define FMO9  1
+#define FMO12 1
+#define FMO18 1
+#define FMO24 1
+
+#define FMBO9  1
+#define FMBO12 1
+#define FMBO18 1
+#define FMBO24 1
+
+#define FSS9  1
+#define FSS12 1
+#define FSS18 1
+#define FSS24 1
+
+#define FSSB9  1
+#define FSSB12 1
+#define FSSB18 1
+#define FSSB24 1
+
+#define FSSO9  1
+#define FSSO12 1
+#define FSSO18 1
+#define FSSO24 1
+
+#define FSSBO9  1
+#define FSSBO12 1
+#define FSSBO18 1
+#define FSSBO24 1
+
+#define FS9  1
+#define FS12 1
+#define FS18 1
+#define FS24 1
+
+#define FSI9  1
+#define FSI12 1
+#define FSI19 1
+#define FSI24 1
+
+#define FSB9  1
+#define FSB12 1
+#define FSB18 1
+#define FSB24 1
+
+#define FSBI9  1
+#define FSBI12 1
+#define FSBI18 1
+#define FSBI24 1
+
+#endif // LOAD_GFXFF