diff --git a/libs/core/dal.d.ts b/libs/core/dal.d.ts
index a01cd452..bf9e6fdd 100644
--- a/libs/core/dal.d.ts
+++ b/libs/core/dal.d.ts
@@ -2,6 +2,7 @@
 declare const enum DAL {
     // built/dockermake/pxtapp/ev3const.h
     NUM_INPUTS = 4,
+    NUM_OUTPUTS = 4,
     LCD_WIDTH = 178,
     LCD_HEIGHT = 128,
     NUM_BUTTONS = 6,
@@ -45,6 +46,7 @@ declare const enum DAL {
     CONN_OUTPUT_TACHO = 125,
     CONN_NONE = 126,
     CONN_ERROR = 127,
+    opProgramStart = 0x03,
     opOutputGetType = 0xA0,
     opOutputSetType = 0xA1,
     opOutputReset = 0xA2,
diff --git a/libs/core/ev3const.h b/libs/core/ev3const.h
index 2a424a29..6c222ff3 100644
--- a/libs/core/ev3const.h
+++ b/libs/core/ev3const.h
@@ -2,6 +2,7 @@
 #define __PXT_EV3CONST_H
 
 #define NUM_INPUTS 4
+#define NUM_OUTPUTS 4
 #define LCD_WIDTH 178
 #define LCD_HEIGHT 128
 #define NUM_BUTTONS 6
@@ -52,6 +53,7 @@
 #define CONN_NONE 126
 #define CONN_ERROR 127
 
+#define opProgramStart 0x03
 #define opOutputGetType 0xA0
 #define opOutputSetType 0xA1
 #define opOutputReset 0xA2
diff --git a/libs/core/output.cpp b/libs/core/output.cpp
index dde7d9bd..bc08bd13 100644
--- a/libs/core/output.cpp
+++ b/libs/core/output.cpp
@@ -1,5 +1,5 @@
 #include "pxt.h"
-#include "ev3.h"
+#include "ev3const.h"
 
 namespace output {
 
@@ -12,18 +12,11 @@ Buffer createBuffer(int size) {
     return mkBuffer(NULL, size);
 }
 
-extern "C" int WriteToPWMDevice(char *bytes, int num_bytes);
-
-//%
-void writePWM(Buffer buf) {
-    WriteToPWMDevice((char *)buf->data, buf->length);
-}
 }
 
 namespace pxt {
 
 void target_init() {
-    OutputInit();
 }
 
 }
diff --git a/libs/core/output.ts b/libs/core/output.ts
index 5213658c..19f5ac93 100644
--- a/libs/core/output.ts
+++ b/libs/core/output.ts
@@ -13,8 +13,34 @@ enum OutputType {
 }
 
 namespace output {
-    //% shim=output::writePWM
-    function writePWM(buf: Buffer): void { }
+    let pwmMM: MMap
+    let motorMM: MMap
+
+    const enum MotorDataOff {
+        TachoCounts = 0, // int32
+        Speed = 4, // int8
+        Padding = 5, // int8[3]
+        TachoSensor = 8, // int32
+        Size = 12
+    }
+
+    function init() {
+        if (pwmMM) return
+        pwmMM = control.mmap("/dev/lms_pwm", 0, 0)
+        if (!pwmMM) control.fail("no PWM file")
+        motorMM = control.mmap("/dev/lms_motor", MotorDataOff.Size * DAL.NUM_OUTPUTS, 0)
+        
+        stop(Output.ALL)
+
+        let buf = output.createBuffer(1)
+        buf[0] = DAL.opProgramStart
+        writePWM(buf)
+    }
+
+    function writePWM(buf: Buffer): void {
+        init()
+        pwmMM.write(buf)
+    }
 
     function mkCmd(out: Output, cmd: number, addSize: number) {
         let b = createBuffer(2 + addSize)
diff --git a/libs/core/pxt.json b/libs/core/pxt.json
index b7d3e261..50e20cee 100644
--- a/libs/core/pxt.json
+++ b/libs/core/pxt.json
@@ -30,11 +30,9 @@
     "testFiles": [
         "test.ts"
     ],
-    "npmDependencies": {
-        "ev3api-bin": "1.1.0"
-    },
+    "npmDependencies": {},
     "public": true,
     "dependencies": {
         "base": "file:../base"
     }
-}
+}
\ No newline at end of file