diff --git a/core/serial.js b/core/serial.js
index f8429e3..f02d4b9 100644
--- a/core/serial.js
+++ b/core/serial.js
@@ -215,32 +215,50 @@ To add a new serial device, you must add an object to
         });
       }
     }, function(data) { // RECEIEVE DATA
-      if (!(data instanceof ArrayBuffer)) console.warn("Serial port implementation is not returning ArrayBuffers");
-      if (Espruino.Config.SERIAL_FLOW_CONTROL) {
-        var u = new Uint8Array(data);
-        for (var i=0;i<u.length;i++) {
-          if (u[i]==17) { // XON
-            console.log("XON received => resume upload");
-            flowControlXOFF = false;
-            if (flowControlTimeout) {
-              clearTimeout(flowControlTimeout);
-              flowControlTimeout = undefined;
+      if (!(data instanceof ArrayBuffer)) console.warn("Serial port implementation is not returning ArrayBuffers")
+
+      // Filter incoming data to handle and remove control characters
+      const filteredData = new Uint8Array(data).filter((v) => {
+        switch (v) {
+          case 17: // XON
+            if (Espruino.Config.SERIAL_FLOW_CONTROL) {
+              console.log("XON received => resume upload")
+              flowControlXOFF = false
+              if (flowControlTimeout) {
+                clearTimeout(flowControlTimeout)
+                flowControlTimeout = undefined
+              }
+            }
+            return false
+
+          case 19: // XOFF
+            if (Espruino.Config.SERIAL_FLOW_CONTROL) {
+              console.log("XOFF received => pause upload")
+              flowControlXOFF = true
+              if (flowControlTimeout) clearTimeout(flowControlTimeout)
+              flowControlTimeout = setTimeout(function () {
+                console.log(
+                  `XOFF timeout (${FLOW_CONTROL_RESUME_TIMEOUT}s) => resume upload anyway`
+                )
+                flowControlXOFF = false
+                flowControlTimeout = undefined
+              }, FLOW_CONTROL_RESUME_TIMEOUT)
             }
-          }
-          if (u[i]==19) { // XOFF
-            console.log("XOFF received => pause upload");
-            flowControlXOFF = true;
-            if (flowControlTimeout)
-              clearTimeout(flowControlTimeout);
-            flowControlTimeout = setTimeout(function() {
-              console.log(`XOFF timeout (${FLOW_CONTROL_RESUME_TIMEOUT}s) => resume upload anyway`);
-              flowControlXOFF = false;
-              flowControlTimeout = undefined;
-            }, FLOW_CONTROL_RESUME_TIMEOUT);
-          }
+            return false
+
+          case 6: // ACK
+            emit("ack")
+            return false
+
+          case 21: // NACK
+            emit("nack")
+            return false
         }
-      }
-      if (readListener) readListener(data);
+
+        return true
+      })
+
+      if (readListener) readListener(filteredData.buffer)
     }, function(error) { // DISCONNECT
       currentDevice = undefined;
       if (writeTimeout!==undefined)
@@ -412,6 +430,45 @@ To add a new serial device, you must add an object to
     }
   };
 
+  /** 
+   * Simplified events system.
+   * @typedef {"close"|"data"|"open"|"error"|"ack"|"nack"|"packet"} PacketEvent
+   * @typedef {(...any) => void} PacketEventListener
+   */
+
+  /** @type {Object.<PacketEvent, PacketEventListener} */
+  var pkListeners = {};
+      
+  /**
+   * Act on events using a simplified events listener
+   * @param {PacketEvent} evt
+   * @param {PacketEventListener} cb 
+   */
+  function on(evt, cb) { 
+    let e = "on" + evt; 
+    if (!pkListeners[e]) pkListeners[e] = []; 
+    pkListeners[e].push(cb); 
+  } 
+
+  /**
+   * Emit event on the event handler, will call all registered callbacks for {evt} and pass {data}
+   * @param {PacketEvent} evt 
+   * @param  {...any} data 
+   */
+  function emit(evt, ...data) { 
+    let e = "on" + evt; 
+    if (pkListeners[e]) pkListeners[e].forEach(fn => fn(...data));
+  }
+
+  /**
+   * Remove a {PacketEvent} listener
+   * @param {PacketEvent} evt 
+   * @param {PacketEventListener} callback 
+   */
+  function removeListener(evt, callback) { 
+    let e = "on" + evt; 
+    if (pkListeners[e]) pkListeners[e] = pkListeners[e].filter(fn => fn != callback);
+  }
 
   // ----------------------------------------------------------
   Espruino.Core.Serial = {
@@ -442,6 +499,9 @@ To add a new serial device, you must add an object to
     },
     "setBinary": function(isOn) {
       sendingBinary = isOn;
-    }
+    },
+
+    // Packet events system
+    on, emit, removeListener
   };
 })();
diff --git a/core/utils.js b/core/utils.js
index b6819ef..f58c705 100644
--- a/core/utils.js
+++ b/core/utils.js
@@ -467,7 +467,181 @@
     }
   }
 
+  /** 
+   * Packet types mapped to their wire values
+   * @typedef {Object} PacketTypes
+   * @property {number} RESPONSE - Response to an EVAL packet
+   * @property {number} EVAL - Execute and return the result as RESPONSE packet
+   * @property {number} EVENT - Parse as JSON and create `E.on('packet', ...)` event
+   * @property {number} FILE_SEND - Called before DATA, with {fn:"filename",s:123}
+   * @property {number} DATA - Sent after FILE_SEND with blocks of data for the file
+   * @property {number} FILE_RECV - Receive a file - returns a series of PT_TYPE_DATA packets, with a final zero length packet to end
+   */
+  const pkTypes = Object.freeze({
+    RESPONSE:  0,     
+    EVAL:      0x2000,
+    EVENT:     0x4000,
+    FILE_SEND: 0x6000,
+    DATA:      0x8000,
+    FILE_RECV: 0xA000 
+  })
+
+  /**
+   * Creates a new packet for transfer using the packet protocol
+   * @param {number} pkType The packet type being sent, from `PacketTypes`
+   * @param {string} data Data to be appended to the end of the packet (max length 8191 bytes)
+   * @returns {string}
+   */
+  function createPacket(pkType, data) {
+    
+    // Check the packet type is one of the known types
+    if (!Object.hasOwn(pkTypes, pkType)) throw new Error(`'pkType' '${pkType}' not one of ${Object.keys(pkTypes)}`);
+
+    // Check the data is a string type and length is in bounds
+    if (typeof data !== 'string') throw new Error("data must be a String");
+    if (data.length <= 0 || data.length > 0x1FFF) throw new Error('data length is out of bounds, max 8191 bytes');
+
+    // Create packet heading using packet type and data length
+    const heading = pkTypes[pkType] | data.length
+
+    return String.fromCharCode(
+      16,                   // DLE (Data Link Escape)
+      1,                    // SOH (Start of Heading)
+      (heading >> 8) &0xFF, // Upper byte of heading
+      heading & 0xFF        // Lower byte of heading
+    ) + data;               // Data blob
+  }
+
+  /**
+   * Take an input buffer and look for the initial control characters and then attempt to parse a 
+   * complete data packet from the buffer. Any complete packet is sent via `emit("packet")` and then
+   * stripped from `buffer` modifiying it.
+   * @param {Uint8Array} buffer 
+   * @returns {Uint8Array}
+   */
+  function parsePacketsFromBuffer(buffer) {
+
+    // Find DLE
+    const dle = buffer.findIndex(v => v === 0x10)
+    if (dle < 0) return buffer
+
+    // Check for SOH
+    if (buffer.at(dle + 1) !== 0x1) {
+      // console.warn("DLE not followed by SOH")
+      // TODO: Not stripping out this invalid control will cause a loop
+      buffer.set([undefined], dle) // Remove this DLE
+      return buffer
+    }
+
+    // Check there's still space for headers
+    if (buffer.at(dle + 2) === undefined || buffer.at(dle + 3) === undefined) {
+      console.warn("NO SPACE FOR HEADERS")
+      return buffer
+    }
+    const upper = buffer.at(dle + 2)
+    const lower = buffer.at(dle + 3)
+
+    // Parse heading from 2 bytes after control headers
+    const heading = new Number(upper << 8) | new Number(lower)
+    const pkLen = heading & 0x1FFF
+    const pkTyp = heading & 0xE000
+
+    // Ignoring heading bytes, check if there's enough bytes in the buffer to satisfy pkLen
+    if (buffer.length < dle + 4 + pkLen) {
+      return buffer
+    }
+
+    // Pick out a packet from the buffer and emit it via the event handler
+    const packet = buffer.subarray(dle, dle + 4 + pkLen)
+    console.log("Packet recieved... type:", pkTyp, "length:", pkLen)
+    Espruino.Core.Serial.emit('packet', pkTyp, packet.subarray(4, packet.length))
+
+    // Fill the buffer region of the packet that was sent with undefined
+    buffer.fill(undefined, 0, dle + packet.length)
+
+    // Return the input buffer but with the stripped packet filtered out
+    return buffer.filter(v => v !== undefined)
+  }
+
+  /**
+   * Send a packet
+   * @param {number} pkType 
+   * @param {string} data 
+   * @param {() => void} callback 
+   */
+  function sendPacket(pkType, data, callback) {
+    
+    function onAck() {
+      // TODO: What do we actually need to do in the event of an ack
+      // tidy()
+      // callback()
+    }
+
+    function onNack(err) {
+      tidy()
+      callback(err)
+    }
+
+    let allData
+    function onPacket(rxPkType, data) {
+      tidy()
+      const packetData = String.fromCharCode(...data)
+
+      // TODO: Depending on the rx type and tx type match up packet types, wait for x number of data
+      if (pkTypes[pkType] === pkTypes.EVAL && rxPkType === pkTypes.RESPONSE) {
+        callback(packetData)
+
+      // If the packet type is data, we need to wait for the 0 length `DATA` packet and then send all of the data joined together
+      } else if (pkTypes[pkType] === pkTypes.FILE_RECV && rxPkType === pkTypes.DATA) {
+        if (data.length === 0) {
+          callback(allData)
+          console.log("zero packet")
+        } else {
+          console.log("appending data", String.fromCharCode(...data))
+          allData += String.fromCharCode(...data)
+        }
+      }else {
+        callback("nodata")
+      }
+    }
+
+    // Tidy up the event listeners from this packet task
+    function tidy() {
+      Espruino.Core.Serial.removeListener("ack", onAck)
+      Espruino.Core.Serial.removeListener("nack", onNack)
+      Espruino.Core.Serial.removeListener("packet", onPacket)
+    }
+
+    // Attach event handlers for this packet event
+    Espruino.Core.Serial.on("ack", onAck)
+    Espruino.Core.Serial.on("nack", onNack)
+    Espruino.Core.Serial.on("packet", onPacket)
+
+    // Write packet to serial port
+    Espruino.Core.Serial.write(createPacket(pkType, data), undefined, function () {
+      // TODO: Add 1 sec timeout
+
+      let dataBuffer = new Uint8Array()
+
+      // Each time data comes in, expand the buffer and add the new data to it
+      // TODO: This seems problematic if there are subsequent/concurrent calls
+      Espruino.Core.Serial.startListening((data) => {
+        const newBuffer = new Uint8Array(data)
+
+        const tempBuffer = new Uint8Array(dataBuffer.length + newBuffer.length)
+        tempBuffer.set(dataBuffer, 0)
+        tempBuffer.set(newBuffer, dataBuffer.length)
+
+        dataBuffer = tempBuffer
+
+        // Now we've added more data to the buffer, try to parse out any packets
+        dataBuffer = parsePacketsFromBuffer(dataBuffer)
+      })
+    })
+  }
+
   /**
+   * Download a file - storageFile or normal file
    * @param {string} fileName Path to file to download
    * @param {(content?: string) => void} callback Call back with contents of file, or undefined if no content
    */
@@ -484,6 +658,10 @@ while (d!==undefined) {console.log(btoa(d));d=f.read(${CHUNKSIZE});}
       }, options);
   }
 
+  function downloadFileV2(fileName, fs, callback) {
+    sendPacket("FILE_RECV", JSON.stringify({ fn: fileName, fs }), callback)
+  }
+
   /**
    * Get the JS needed to upload a file
    * @param {string} fileName Path to file to upload
@@ -1116,8 +1294,10 @@ while (d!==undefined) {console.log(btoa(d));d=f.read(${CHUNKSIZE});}
       countBrackets : countBrackets,
       getEspruinoPrompt : getEspruinoPrompt,
       executeExpression : function(expr,callback) { executeExpression(expr,callback,{exprPrintsResult:false}); },
+      executeExpressionV2: function(expr,callback) { sendPacket("EVAL",expr,callback); /* TODO: Callback and parseRJSON */ },
       executeStatement : function(statement,callback) { executeExpression(statement,callback,{exprPrintsResult:true}); },
       downloadFile : downloadFile, // (fileName, callback)
+      downloadFileV2 : downloadFileV2,
       getUploadFileCode : getUploadFileCode, //(fileName, contents);
       uploadFile : uploadFile, // (fileName, contents, callback)
       versionToFloat : versionToFloat,
@@ -1143,6 +1323,7 @@ while (d!==undefined) {console.log(btoa(d));d=f.read(${CHUNKSIZE});}
       asUTF8Bytes : asUTF8Bytes,
       isASCII : isASCII,
       btoa : btoa,
-      atob : atob
+      atob : atob,
+      createPacket : createPacket
   };
 }());