diff --git a/package.json b/package.json
index a34738e..8772eee 100644
--- a/package.json
+++ b/package.json
@@ -8,7 +8,8 @@
     "start": "ionic-app-scripts serve",
     "clean": "ionic-app-scripts clean",
     "build": "ionic-app-scripts build",
-    "android:deploy": "ionic cordova build android; adb install -r platforms/android/app/build/outputs/apk/debug/app-debug.apk",
+    "android:build": "ionic cordova build android",
+    "android:deploy": "adb install -r platforms/android/app/build/outputs/apk/debug/app-debug.apk",
     "android:start": "adb shell am force-stop io.ionic.starter; adb shell am start -n io.ionic.starter/io.ionic.starter.MainActivity; sleep 1; adb logcat | grep -F \"`adb shell ps | grep io.ionic.starter | cut -c15-18`\"",
     "lint": "ionic-app-scripts lint"
   },
diff --git a/src/pages/ota-wizard/ota-wizard.ts b/src/pages/ota-wizard/ota-wizard.ts
index a3209a0..6f1e361 100644
--- a/src/pages/ota-wizard/ota-wizard.ts
+++ b/src/pages/ota-wizard/ota-wizard.ts
@@ -29,7 +29,7 @@ export class OtaWizardPage implements OnInit, OnDestroy {
   sketch = ''
   filterSsids = true
   availableSenseboxes: string[] = [] // list of SSIDs
-  compiledSketch = undefined
+  compiledSketch: ArrayBuffer = undefined
   errorMsg = ''
 
   state: OtaState = {
@@ -127,10 +127,13 @@ export class OtaWizardPage implements OnInit, OnDestroy {
   }
 
   private handleCompilation () {
+    // skip compilation slide if already compiled
     this.slides.lockSwipeToNext(!this.compiledSketch)
+    if (this.compiledSketch)
+      return this.slides.slideNext(0)
 
     // need to go online for compilation. compilation is retriggered via this.onlineSub
-    if (!this.compiledSketch && !this.state.isOnline) {
+    if (!this.state.isOnline) {
       switch (this.otaWifi.strategy) {
         case WifiStrategy.Automatic:
           // TODO: auto connect to previous network, if available
@@ -138,6 +141,8 @@ export class OtaWizardPage implements OnInit, OnDestroy {
           this.state.compilation = 'go-online'
           break
       }
+    } else {
+      this.compileSketch()
     }
   }
 
@@ -182,7 +187,12 @@ export class OtaWizardPage implements OnInit, OnDestroy {
       this.slides.lockSwipeToNext(false)
     } catch (err) {
       this.state.compilation = 'error'
-      this.errorMsg = err.message
+      this.errorMsg = !err.message ? err : err.message
+        .replace(/&/g, '&')
+        .replace(/</g, '&lt;')
+        .replace(/>/g, '&gt;')
+        .replace(/"/g, '&quot;')
+        .replace(/\n/g, '<br/>')
     }
   }
 }
diff --git a/src/providers/compiler/compiler.ts b/src/providers/compiler/compiler.ts
index ab009bb..9ea9d66 100644
--- a/src/providers/compiler/compiler.ts
+++ b/src/providers/compiler/compiler.ts
@@ -1,7 +1,9 @@
-import { HttpClient,HttpHeaders }  from '@angular/common/http';
+import { HttpClient, HttpHeaders } from '@angular/common/http';
 import { Injectable } from '@angular/core';
+import { timeout } from 'rxjs/operators'
 
-const URL = "https://compiler.sensebox.de"
+// const URL = "https://compiler.sensebox.de"
+const URL = "http://compiler.snsbx.nroo.de"
 
 @Injectable()
 export class CompilerProvider {
@@ -10,23 +12,28 @@ export class CompilerProvider {
     console.log('Hello CompilerProvider Provider');
   }
 
-  async callcompiler(sketch : string): Promise<any> {
+  async callcompiler(sketch : string): Promise<ArrayBuffer> {
     const headers =  new HttpHeaders({'Content-Type': 'application/json'} );
     const data = { board: 'sensebox-mcu', sketch }
 
     // send compilation request, returning a job ID
-    return this.http.post(`${URL}/compile`, data, { headers }).toPromise()
+    return this.http.post(`${URL}/compile`, data, { headers })
+      .pipe(timeout(4000))
+      .toPromise()
       .catch(err => {
-        let msg = ''
-        try { msg = JSON.parse(err.error.message).process } catch (err) {}
-        throw new Error(msg || err)
+        let msg = 'unable to contact web compiler. are you online?'
+        try {
+          // attempt to extract the compilation error message and clean it up
+          msg = JSON.parse(err.error.message).process
+          msg = `compilation error: ${msg.substr(msg.indexOf(' ') + 14)}`
+          msg = msg.substr(0, msg.indexOf('^'))
+        } catch (err) {}
+        throw Error(msg)
       })
-      .then((response:any) =>{
-        // download the resulting sketch binary
-        return this.http.get(`${URL}/download?id=${response.data.id}&board=sensebox-mcu`, {
-          responseType: 'text',
-        }).toPromise()
-
+      // download the resulting sketch binary
+      .then((response: any) => {
+        const url = `${URL}/download?id=${response.data.id}&board=sensebox-mcu`
+        return this.http.get(url, { responseType: 'arraybuffer' }).toPromise()
       });
   };
 }
diff --git a/src/providers/ota-wifi/ota-wifi.ts b/src/providers/ota-wifi/ota-wifi.ts
index 21dbbdb..3559d57 100644
--- a/src/providers/ota-wifi/ota-wifi.ts
+++ b/src/providers/ota-wifi/ota-wifi.ts
@@ -62,12 +62,12 @@ export class OtaWifiProvider {
       : WifiWizard2.connect(ssid, true)
   }
 
-  async uploadFirmware (binary: string): Promise<any> {
+  async uploadFirmware (binary: ArrayBuffer): Promise<any> {
     // TODO: send checksum?
-    return this.http.post(`${SENSEBOX_API}/flash`, binary, {
+    return this.http.post(`${SENSEBOX_API}/sketch`, binary, {
       responseType: 'text',
     })
-      .pipe(timeout(2500), catchError(err => {
+      .pipe(timeout(5000), catchError(err => {
         throw new Error('senseBox not found. Is it running in OTA mode?')
       }))
       .toPromise()