diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 3521f20..3689298 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -13,7 +13,7 @@ jobs:
           node-version: '14.x'
           registry-url: 'https://registry.npmjs.org'
       - name: Install dependencies and build 🔧
-        run: npm install && npm run build
+        run: npm ci && npm run build
       - name: Run tests 
         run: npm run test
       - name: Package .vsix
diff --git a/favicon.ico b/favicon.ico
new file mode 100644
index 0000000..520ef4b
Binary files /dev/null and b/favicon.ico differ
diff --git a/index.js b/index.js
index 4e12ff7..8899043 100644
--- a/index.js
+++ b/index.js
@@ -17,7 +17,7 @@ const table = document.getElementById('fileTable');
 const alertDiv = document.getElementById('alertDiv');
 
 // import { Transport } from './cp210x-webusb.js'
-import esptooljs from "./bundle.js";
+import * as esptooljs from "./bundle.js";
 const ESPLoader = esptooljs.ESPLoader;
 const Transport = esptooljs.Transport;
 
@@ -78,16 +78,16 @@ function _sleep(ms) {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }
 
-function terminalClearFn() {
-  term.clear();
-}
-
-function terminalWrite(data) {
-  term.write(data);
-}
-
-function terminalWriteLn(data) {
-  term.writeln(data);
+let espLoaderTerminal = {
+  clean() {
+    term.clear();
+  },
+  writeLine(data) {
+    term.writeln(data);
+  },
+  write(data) {
+    term.write(data)
+  }
 }
 
 connectButton.onclick = async () => {
@@ -101,7 +101,7 @@ connectButton.onclick = async () => {
   }
 
   try {
-    esploader = new ESPLoader(transport, baudrates.value, terminalClearFn, terminalWriteLn, terminalWrite);
+    esploader = new ESPLoader(transport, baudrates.value, espLoaderTerminal);
     connected = true;
 
     chip = await esploader.main_fn();
diff --git a/package-lock.json b/package-lock.json
index 29b89d1..0b7d989 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -10,6 +10,7 @@
       "dependencies": {
         "crypto-js": "^4.0.0",
         "pako": "^2.1.0",
+        "tslib": "^2.4.1",
         "xterm": "^4.13.0"
       },
       "devDependencies": {
@@ -3333,10 +3334,9 @@
       }
     },
     "node_modules/tslib": {
-      "version": "1.14.1",
-      "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.14.1.tgz",
-      "integrity": "sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==",
-      "dev": true
+      "version": "2.4.1",
+      "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.4.1.tgz",
+      "integrity": "sha512-tGyy4dAjRIEwI7BzsB0lynWgOpfqjUdq91XXAlIWD2OwKBH7oCl/GZG/HT4BOHrTlPMOASlMQ7veyTqpmRcrNA=="
     },
     "node_modules/tsutils": {
       "version": "3.21.0",
@@ -3353,6 +3353,12 @@
         "typescript": ">=2.8.0 || >= 3.2.0-dev || >= 3.3.0-dev || >= 3.4.0-dev || >= 3.5.0-dev || >= 3.6.0-dev || >= 3.6.0-beta || >= 3.7.0-dev || >= 3.7.0-beta"
       }
     },
+    "node_modules/tsutils/node_modules/tslib": {
+      "version": "1.14.1",
+      "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.14.1.tgz",
+      "integrity": "sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==",
+      "dev": true
+    },
     "node_modules/type-check": {
       "version": "0.4.0",
       "resolved": "https://registry.npmjs.org/type-check/-/type-check-0.4.0.tgz",
@@ -5982,10 +5988,9 @@
       }
     },
     "tslib": {
-      "version": "1.14.1",
-      "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.14.1.tgz",
-      "integrity": "sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==",
-      "dev": true
+      "version": "2.4.1",
+      "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.4.1.tgz",
+      "integrity": "sha512-tGyy4dAjRIEwI7BzsB0lynWgOpfqjUdq91XXAlIWD2OwKBH7oCl/GZG/HT4BOHrTlPMOASlMQ7veyTqpmRcrNA=="
     },
     "tsutils": {
       "version": "3.21.0",
@@ -5994,6 +5999,14 @@
       "dev": true,
       "requires": {
         "tslib": "^1.8.1"
+      },
+      "dependencies": {
+        "tslib": {
+          "version": "1.14.1",
+          "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.14.1.tgz",
+          "integrity": "sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==",
+          "dev": true
+        }
       }
     },
     "type-check": {
diff --git a/package.json b/package.json
index 16a1d28..a331c34 100644
--- a/package.json
+++ b/package.json
@@ -29,6 +29,7 @@
   "dependencies": {
     "crypto-js": "^4.0.0",
     "pako": "^2.1.0",
+    "tslib": "^2.4.1",
     "xterm": "^4.13.0"
   },
   "devDependencies": {
diff --git a/src/espLoader.ts b/src/espLoader.ts
index 13033cc..e2ddd0d 100644
--- a/src/espLoader.ts
+++ b/src/espLoader.ts
@@ -17,12 +17,18 @@ const MAGIC_TO_CHIP: { [key: number]: ROM } = {
   0xfff0c101: new ESP8266ROM(),
 };
 
-interface ESPBinFile {
+export interface ESPBinFile {
   data: string;
   address: number;
 }
 
-class ESPLoader {
+export interface IEspLoaderTerminal {
+  clean: () => void;
+  writeLine: (data: string) => void;
+  write: (data: string) => void;
+}
+
+export class ESPLoader {
   ESP_RAM_BLOCK = 0x1800;
   ESP_FLASH_BEGIN = 0x02;
   ESP_FLASH_DATA = 0x03;
@@ -76,17 +82,14 @@ class ESPLoader {
   constructor(
     public transport: Transport,
     private baudrate: number,
-    private terminalCleanFn: () => void,
-    private terminalWriteLineFn: (data: string) => void,
-    private terminalWriteFn: (data: string) => void,
+    private terminal: IEspLoaderTerminal,
     private rom_baudrate = 115200,
   ) {
     this.IS_STUB = false;
-    this.chip = new ESP32ROM();
+    this.chip = null;
     this.FLASH_WRITE_SIZE = 0x4000;
-
-    if (this.terminalCleanFn) {
-      this.terminalCleanFn();
+    if (this.terminal) {
+      this.terminal.clean();
     }
 
     this.log("esptool.js v0.1-dev");
@@ -98,16 +101,16 @@ class ESPLoader {
   }
 
   log(str: string) {
-    if (this.terminalWriteLineFn) {
-      this.terminalWriteLineFn(str);
+    if (this.terminal) {
+      this.terminal.writeLine(str);
     } else {
       // eslint-disable-next-line no-console
       console.log(str);
     }
   }
   write_char(str: string) {
-    if (this.terminalWriteFn) {
-      this.terminalWriteFn(str);
+    if (this.terminal) {
+      this.terminal.write(str);
     } else {
       // eslint-disable-next-line no-console
       console.log(str);
@@ -1004,5 +1007,3 @@ class ESPLoader {
     }
   }
 }
-
-export default ESPLoader;
diff --git a/src/index.ts b/src/index.ts
index 2bc03a1..2f01753 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,4 +1,2 @@
-import ESPLoader from "./espLoader";
-import { Transport } from "./webserial";
-
-export default { ESPLoader, Transport };
+export { IEspLoaderTerminal, ESPLoader } from "./esploader";
+export { Transport } from "./webserial";
diff --git a/src/targets/esp32.ts b/src/targets/esp32.ts
index 7464844..5a314c4 100644
--- a/src/targets/esp32.ts
+++ b/src/targets/esp32.ts
@@ -1,4 +1,4 @@
-import ESPLoader from "../espLoader";
+import { ESPLoader } from "../esploader";
 import { ROM } from "./rom";
 
 export default class ESP32ROM extends ROM {
@@ -96,20 +96,20 @@ export default class ESP32ROM extends ROM {
     "YjiDW+mNANzr1LUT2ElJKyOShBjc24Bubh7Lmjp/Eifg5awjAiP9ZbJfx620qNfq" +
     "wqvdldrZOj9LCYJ8mer+L0DR4a0UDQAA";
 
-  public read_efuse = async (loader: ESPLoader, offset: number) => {
+  public async read_efuse(loader: ESPLoader, offset: number) {
     const addr = this.EFUSE_RD_REG_BASE + 4 * offset;
     loader.log("Read efuse " + addr);
     return await loader.read_reg(addr);
   };
 
-  public get_pkg_version = async (loader: ESPLoader) => {
+  public async get_pkg_version(loader: ESPLoader) {
     const word3 = await this.read_efuse(loader, 3);
     let pkg_version = (word3 >> 9) & 0x07;
     pkg_version += ((word3 >> 2) & 0x1) << 3;
     return pkg_version;
   };
 
-  public get_chip_revision = async (loader: ESPLoader) => {
+  public async get_chip_revision(loader: ESPLoader) {
     const word3 = await this.read_efuse(loader, 3);
     const word5 = await this.read_efuse(loader, 5);
     const apb_ctl_date = await loader.read_reg(this.DR_REG_SYSCON_BASE + 0x7c);
@@ -131,7 +131,7 @@ export default class ESP32ROM extends ROM {
     return 0;
   };
 
-  public get_chip_description = async (loader: ESPLoader) => {
+  public async get_chip_description(loader: ESPLoader) {
     const chip_desc = [
       "ESP32-D0WDQ6",
       "ESP32-D0WD",
@@ -166,7 +166,7 @@ export default class ESP32ROM extends ROM {
     return chip_name + " (revision " + chip_revision + ")";
   };
 
-  public get_chip_features = async (loader: ESPLoader) => {
+  public async get_chip_features(loader: ESPLoader) {
     const features = ["Wi-Fi"];
     const word3 = await this.read_efuse(loader, 3);
 
@@ -220,7 +220,7 @@ export default class ESP32ROM extends ROM {
     return features;
   };
 
-  public get_crystal_freq = async (loader: ESPLoader) => {
+  public async get_crystal_freq(loader: ESPLoader) {
     const uart_div = (await loader.read_reg(this.UART_CLKDIV_REG)) & this.UART_CLKDIV_MASK;
     const ets_xtal = (loader.transport.baudrate * uart_div) / 1000000 / this.XTAL_CLK_DIVIDER;
     let norm_xtal;
@@ -240,7 +240,7 @@ export default class ESP32ROM extends ROM {
     return h.length === 1 ? "0" + h : h;
   }
 
-  public read_mac = async (loader: ESPLoader) => {
+  public async read_mac(loader: ESPLoader) {
     let mac0 = await this.read_efuse(loader, 1);
     mac0 = mac0 >>> 0;
     let mac1 = await this.read_efuse(loader, 2);
diff --git a/src/targets/esp32c3.ts b/src/targets/esp32c3.ts
index edd1fab..9967e7f 100644
--- a/src/targets/esp32c3.ts
+++ b/src/targets/esp32c3.ts
@@ -1,4 +1,4 @@
-import ESPLoader from "../espLoader";
+import { ESPLoader } from "../esploader";
 import { ROM } from "./rom";
 
 export default class ESP32C3ROM extends ROM {
@@ -94,7 +94,7 @@ export default class ESP32C3ROM extends ROM {
     "pnltVv+9jvHXkU4sXKfxG0NqhL7U68N6/PpKeyfjl0o+XMA5N/wc9+g6UfWl9s83" +
     "J279YCuxbUpfYBg26DI+z0jM/CCTyLqft1P4h/4HprTSLAwNAAA=";
 
-  public get_pkg_version = async (loader: ESPLoader) => {
+  public async get_pkg_version(loader: ESPLoader) {
     const num_word = 3;
     const block1_addr = this.EFUSE_BASE + 0x044;
     const addr = block1_addr + 4 * num_word;
@@ -103,7 +103,7 @@ export default class ESP32C3ROM extends ROM {
     return pkg_version;
   };
 
-  public get_chip_revision = async (loader: ESPLoader) => {
+  public async get_chip_revision(loader: ESPLoader) {
     const block1_addr = this.EFUSE_BASE + 0x044;
     const num_word = 3;
     const pos = 18;
@@ -112,7 +112,7 @@ export default class ESP32C3ROM extends ROM {
     return ret;
   };
 
-  public get_chip_description = async (loader: ESPLoader) => {
+  public async get_chip_description(loader: ESPLoader) {
     let desc;
     const pkg_ver = await this.get_pkg_version(loader);
     if (pkg_ver === 0) {
@@ -125,11 +125,11 @@ export default class ESP32C3ROM extends ROM {
     return desc;
   };
 
-  public get_chip_features = async (loader: ESPLoader) => {
+  public async get_chip_features(loader: ESPLoader) {
     return ["Wi-Fi"];
   };
 
-  public get_crystal_freq = async (loader: ESPLoader) => {
+  public async get_crystal_freq(loader: ESPLoader) {
     return 40;
   };
 
@@ -138,7 +138,7 @@ export default class ESP32C3ROM extends ROM {
     return h.length === 1 ? "0" + h : h;
   }
 
-  public read_mac = async (loader: ESPLoader) => {
+  public async read_mac(loader: ESPLoader) {
     let mac0 = await loader.read_reg(this.MAC_EFUSE_REG);
     mac0 = mac0 >>> 0;
     let mac1 = await loader.read_reg(this.MAC_EFUSE_REG + 4);
@@ -166,7 +166,7 @@ export default class ESP32C3ROM extends ROM {
     );
   };
 
-  public get_erase_size = function (offset: number, size: number) {
+  public get_erase_size(offset: number, size: number) {
     return size;
   };
 }
diff --git a/src/targets/esp32s2.ts b/src/targets/esp32s2.ts
index 61acd83..9812c58 100644
--- a/src/targets/esp32s2.ts
+++ b/src/targets/esp32s2.ts
@@ -1,4 +1,4 @@
-import ESPLoader from "../espLoader";
+import { ESPLoader } from "../esploader";
 import { ROM } from "./rom";
 
 export default class ESP32S2ROM extends ROM {
@@ -104,7 +104,7 @@ export default class ESP32S2ROM extends ROM {
     "5lUGBV+inIf/Am8w8EfhMoci6RMleHnQiuD71XzwevARlL/cmi84gg9/L+TC1aFI" +
     "PhaAOeuxgvFPCyIcXl5oXscBJKBdOTgbirB0QdA+obr/HyfMWQisDwAA";
 
-  public get_pkg_version = async (loader: ESPLoader) => {
+  public async get_pkg_version(loader: ESPLoader) {
     const num_word = 3;
     const block1_addr = this.EFUSE_BASE + 0x044;
     const addr = block1_addr + 4 * num_word;
@@ -113,7 +113,7 @@ export default class ESP32S2ROM extends ROM {
     return pkg_version;
   };
 
-  public get_chip_description = async (loader: ESPLoader) => {
+  public async get_chip_description(loader: ESPLoader) {
     const chip_desc = ["ESP32-S2", "ESP32-S2FH16", "ESP32-S2FH32"];
     const pkg_ver = await this.get_pkg_version(loader);
     if (pkg_ver >= 0 && pkg_ver <= 2) {
@@ -123,7 +123,7 @@ export default class ESP32S2ROM extends ROM {
     }
   };
 
-  public get_chip_features = async (loader: ESPLoader) => {
+  public async get_chip_features(loader: ESPLoader) {
     const features = ["Wi-Fi"];
     const pkg_ver = await this.get_pkg_version(loader);
     if (pkg_ver == 1) {
@@ -143,14 +143,14 @@ export default class ESP32S2ROM extends ROM {
     return features;
   };
 
-  public get_crystal_freq = async (loader: ESPLoader) => {
+  public async get_crystal_freq(loader: ESPLoader) {
     return 40;
   };
   public _d2h(d: number) {
     const h = (+d).toString(16);
     return h.length === 1 ? "0" + h : h;
   }
-  public read_mac = async (loader: ESPLoader) => {
+  public async read_mac(loader: ESPLoader) {
     let mac0 = await loader.read_reg(this.MAC_EFUSE_REG);
     mac0 = mac0 >>> 0;
     let mac1 = await loader.read_reg(this.MAC_EFUSE_REG + 4);
@@ -178,7 +178,7 @@ export default class ESP32S2ROM extends ROM {
     );
   };
 
-  public override get_erase_size(offset: number, size: number) {
+  public get_erase_size(offset: number, size: number) {
     return size;
   }
 }
diff --git a/src/targets/esp32s3.ts b/src/targets/esp32s3.ts
index c621fab..fe38ea9 100644
--- a/src/targets/esp32s3.ts
+++ b/src/targets/esp32s3.ts
@@ -1,4 +1,4 @@
-import ESPLoader from "../espLoader";
+import { ESPLoader } from "../esploader";
 import { ROM } from "./rom";
 
 export default class ESP32S3ROM extends ROM {
@@ -119,13 +119,13 @@ export default class ESP32S3ROM extends ROM {
     "A6EOOkSXLzPI/0905+E35NsMZL5N2dQx7VQhTldrENTvyi1fQDWenT4lm8tQK+l3" +
     "KW+3NnXYMAdbYwkNHP1ZTgd8RtiVeVq1Sv50vbRlrKlDTZc48SKV/f8Zky2A";
 
-  public get_chip_description = async (loader: ESPLoader) => {
+  public async get_chip_description(loader: ESPLoader) {
     return "ESP32-S3";
   };
-  public get_chip_features = async (loader: ESPLoader) => {
+  public async get_chip_features(loader: ESPLoader) {
     return ["Wi-Fi", "BLE"];
   };
-  public get_crystal_freq = async (loader: ESPLoader) => {
+  public async get_crystal_freq(loader: ESPLoader) {
     return 40;
   };
   public _d2h(d: number) {
@@ -133,7 +133,7 @@ export default class ESP32S3ROM extends ROM {
     return h.length === 1 ? "0" + h : h;
   }
 
-  public _post_connect = async (loader: ESPLoader) => {
+  public async _post_connect(loader: ESPLoader) {
     const buf_no = (await loader.read_reg(this.UARTDEV_BUF_NO)) & 0xff;
     console.log("In _post_connect " + buf_no);
     if (buf_no == this.UARTDEV_BUF_NO_USB) {
@@ -141,7 +141,7 @@ export default class ESP32S3ROM extends ROM {
     }
   };
 
-  public read_mac = async (loader: ESPLoader) => {
+  public async read_mac(loader: ESPLoader) {
     let mac0 = await loader.read_reg(this.MAC_EFUSE_REG);
     mac0 = mac0 >>> 0;
     let mac1 = await loader.read_reg(this.MAC_EFUSE_REG + 4);
@@ -169,7 +169,7 @@ export default class ESP32S3ROM extends ROM {
     );
   };
 
-  public get_erase_size = function (offset: number, size: number) {
+  public get_erase_size(offset: number, size: number) {
     return size;
   };
 }
diff --git a/src/targets/esp8266.ts b/src/targets/esp8266.ts
index e0ad876..716af2f 100644
--- a/src/targets/esp8266.ts
+++ b/src/targets/esp8266.ts
@@ -1,4 +1,4 @@
-import ESPLoader from "../espLoader";
+import { ESPLoader } from "../esploader";
 import { ROM } from "./rom";
 
 export default class ESP8266ROM extends ROM {
@@ -185,13 +185,13 @@ export default class ESP8266ROM extends ROM {
     "J4beSjfPH4hJ+tFtSdkibccBEOH+kJSrSew2MdSz8C5GWch459cfjuMcT0Pvo0yI" +
     "bcqT/wWthFLmqB8AAA==";
 
-  public read_efuse = async (loader: ESPLoader, offset: number) => {
+  public async read_efuse(loader: ESPLoader, offset: number) {
     const addr = this.EFUSE_RD_REG_BASE + 4 * offset;
     console.log("Read efuse " + addr);
     return await loader.read_reg(addr);
   };
 
-  public get_chip_description = async (loader: ESPLoader) => {
+  public async get_chip_description(loader: ESPLoader) {
     const efuse3 = await this.read_efuse(loader, 2);
     const efuse0 = await this.read_efuse(loader, 0);
 
@@ -205,7 +205,7 @@ export default class ESP8266ROM extends ROM {
     return features;
   };
 
-  public get_crystal_freq = async (loader: ESPLoader) => {
+  public async get_crystal_freq(loader: ESPLoader) {
     const uart_div = (await loader.read_reg(this.UART_CLKDIV_REG)) & this.UART_CLKDIV_MASK;
     const ets_xtal = (loader.transport.baudrate * uart_div) / 1000000 / this.XTAL_CLK_DIVIDER;
     let norm_xtal;
@@ -231,7 +231,7 @@ export default class ESP8266ROM extends ROM {
     return h.length === 1 ? "0" + h : h;
   }
 
-  public read_mac = async (loader: ESPLoader) => {
+  public async read_mac(loader: ESPLoader) {
     let mac0 = await this.read_efuse(loader, 0);
     mac0 = mac0 >>> 0;
     let mac1 = await this.read_efuse(loader, 1);
@@ -275,7 +275,7 @@ export default class ESP8266ROM extends ROM {
     );
   };
 
-  public get_erase_size = function (offset: number, size: number) {
+  public get_erase_size(offset: number, size: number) {
     return size;
   };
 }
diff --git a/src/targets/rom.ts b/src/targets/rom.ts
index 4d6c3b6..b055ed3 100644
--- a/src/targets/rom.ts
+++ b/src/targets/rom.ts
@@ -1,24 +1,4 @@
-import ESPLoader from "../espLoader";
-
-export enum FLASH_SIZES {
-  "1MB" = 0x00,
-  "2MB" = 0x10,
-  "4MB" = 0x20,
-  "8MB" = 0x30,
-  "16MB" = 0x40,
-}
-
-export enum ESP8266_FLASH_SIZES {
-  "512KB" = 0x00,
-  "256KB" = 0x10,
-  "1MB" = 0x20,
-  "2MB" = 0x30,
-  "4MB" = 0x40,
-  "2MB-c1" = 0x50,
-  "4MB-c1" = 0x60,
-  "8MB" = 0x80,
-  "16MB" = 0x90,
-}
+import { ESPLoader } from "../esploader";
 
 export abstract class ROM {
   // abstract read_efuse(loader: ESPLoader, offset: number): Promise<number>; //esp32
@@ -43,13 +23,7 @@ export abstract class ROM {
     return size;
   }
 
-  FLASH_SIZES: { [key: string]: number } = {
-    "1MB": 0x00,
-    "2MB": 0x10,
-    "4MB": 0x20,
-    "8MB": 0x30,
-    "16MB": 0x40,
-  };
+  abstract FLASH_SIZES: { [key: string]: number };
 
   abstract BOOTLOADER_FLASH_OFFSET: number;
   abstract CHIP_NAME: string;
diff --git a/tsconfig.json b/tsconfig.json
index 0186fa6..46d7e86 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,12 +1,13 @@
 {
   "compilerOptions": {
-    "module": "commonjs",
-    "target": "ES5",
+    "module": "ES2020",
+    "target": "ES2019",
     "declaration": true,
     "allowSyntheticDefaultImports": true,
     "outDir": "./lib",
     "moduleResolution": "node",
-    "lib": ["ES2020", "DOM"]
+    "lib": ["ES2020", "DOM"],
+    "importHelpers": true
   },
   "include": ["src/**/*"]
 }
\ No newline at end of file