diff --git a/src/extensions/scratch3_ev3/index.js b/src/extensions/scratch3_ev3/index.js
index 9b1bcba02..b11c8d526 100644
--- a/src/extensions/scratch3_ev3/index.js
+++ b/src/extensions/scratch3_ev3/index.js
@@ -682,6 +682,10 @@ class EV3 {
         const array = Base64Util.base64ToUint8Array(message);
         // log.info(`received array: ${array}`);
 
+        if (array.length < 35) { // TODO: find safer solution
+            return; // don't parse results that aren't sensor data list or device list
+        }
+
         if (this._updateDevices) {
             // READ DEVICE LIST
             this._sensorPorts[0] = EV_DEVICE_TYPES[array[5]] ? EV_DEVICE_TYPES[array[5]] : 'none';
diff --git a/src/extensions/scratch3_microbit/index.js b/src/extensions/scratch3_microbit/index.js
index 1501380d1..c714f1346 100644
--- a/src/extensions/scratch3_microbit/index.js
+++ b/src/extensions/scratch3_microbit/index.js
@@ -24,6 +24,8 @@ const BLECommand = {
     CMD_DISPLAY_LED: 0x82
 };
 
+const BLETimeout = 4500; // TODO: might need tweaking based on how long the device takes to start sending data
+
 /**
  * Enum for micro:bit protocol.
  * https://github.com/LLK/scratch-microbit-firmware/blob/master/protocol.md
@@ -98,6 +100,13 @@ class MicroBit {
                 timeout: false
             }
         };
+
+        /**
+         * Interval ID for data reading timeout.
+         * @type {number}
+         * @private
+         */
+        this._timeoutID = null;
     }
 
     // TODO: keep here?
@@ -122,6 +131,7 @@ class MicroBit {
     }
 
     disconnectSession () {
+        window.clearInterval(this._timeoutID);
         this._ble.disconnectSession();
     }
 
@@ -209,6 +219,7 @@ class MicroBit {
     _onSessionConnect () {
         const callback = this._processSessionData.bind(this);
         this._ble.read(BLEUUID.service, BLEUUID.rxChar, true, callback);
+        this._timeoutID = window.setInterval(this.disconnectSession.bind(this), BLETimeout);
     }
 
     /**
@@ -217,6 +228,7 @@ class MicroBit {
      * @private
      */
     _processSessionData (base64) {
+        // parse data
         const data = Base64Util.base64ToUint8Array(base64);
 
         this._sensors.tiltX = data[1] | (data[0] << 8);
@@ -232,6 +244,10 @@ class MicroBit {
         this._sensors.touchPins[2] = data[8];
 
         this._sensors.gestureState = data[9];
+
+        // cancel disconnect timeout and start a new one
+        window.clearInterval(this._timeoutID);
+        this._timeoutID = window.setInterval(this.disconnectSession.bind(this), BLETimeout);
     }
 
     /**
diff --git a/src/io/bleSession.js b/src/io/bleSession.js
index 5ba95742f..357b80ef6 100644
--- a/src/io/bleSession.js
+++ b/src/io/bleSession.js
@@ -1,5 +1,5 @@
 const JSONRPCWebSocket = require('../util/jsonrpc-web-socket');
-const log = require('../util/log');
+// const log = require('../util/log');
 const ScratchLinkWebSocket = 'wss://device-manager.scratch.mit.edu:20110/scratch/ble';
 
 class BLESession extends JSONRPCWebSocket {
@@ -144,9 +144,9 @@ class BLESession extends JSONRPCWebSocket {
             });
     }
 
-    _sendError (e) {
+    _sendError (/* e */) {
         this._connected = false;
-        log.error(`BLESession error: ${JSON.stringify(e)}`);
+        // log.error(`BLESession error: ${JSON.stringify(e)}`);
         this._runtime.emit(this._runtime.constructor.PERIPHERAL_ERROR);
     }
 
diff --git a/src/io/btSession.js b/src/io/btSession.js
index f2cc54732..849e3032b 100644
--- a/src/io/btSession.js
+++ b/src/io/btSession.js
@@ -1,5 +1,5 @@
 const JSONRPCWebSocket = require('../util/jsonrpc-web-socket');
-const log = require('../util/log');
+// const log = require('../util/log');
 const ScratchLinkWebSocket = 'wss://device-manager.scratch.mit.edu:20110/scratch/bt';
 
 class BTSession extends JSONRPCWebSocket {
@@ -112,9 +112,9 @@ class BTSession extends JSONRPCWebSocket {
         }
     }
 
-    _sendError (e) {
+    _sendError (/* e */) {
         this._connected = false;
-        log.error(`BTSession error: ${JSON.stringify(e)}`);
+        // log.error(`BTSession error: ${JSON.stringify(e)}`);
         this._runtime.emit(this._runtime.constructor.PERIPHERAL_ERROR);
     }