diff --git a/sim/allocator.ts b/sim/allocator.ts
index de1b0cd4..dd23e33b 100644
--- a/sim/allocator.ts
+++ b/sim/allocator.ts
@@ -148,6 +148,16 @@ namespace pxsim {
                 let idx = <number>location[1];
                 let pin = opts.cmpGPIOPins[idx];
                 return {type: "dalboard", pin: pin};
+            } else if (location === "MOSI" || location === "MISO" || location === "SCK") {
+                if (!this.opts.boardDef.spiPins)
+                    console.debug("No SPI pin mappings found!");
+                let pin = (<any>this.opts.boardDef.spiPins)[location as string] as string;
+                return {type: "dalboard", pin: pin};
+            } else if (location === "SDA" || location === "SCL") {
+                if (!this.opts.boardDef.i2cPins)
+                    console.debug("No I2C pin mappings found!");
+                let pin = (<any>this.opts.boardDef.i2cPins)[location as string] as string;
+                return {type: "dalboard", pin: pin};
             } else {
                 //TODO
                 U.assert(false);
@@ -206,7 +216,7 @@ namespace pxsim {
                 let l = this.allocateLocation(ends[idx], {
                     nearestBBPin: locInst.rowCol,
                     startColumn: opts.startColumn,
-                    cmpGPIOPins: opts.cmpGPIOPins
+                    cmpGPIOPins: opts.cmpGPIOPins,
                 });
                 return l;
             });
diff --git a/sim/definitions.ts b/sim/definitions.ts
index a4ede8ba..154f4001 100644
--- a/sim/definitions.ts
+++ b/sim/definitions.ts
@@ -12,8 +12,7 @@ namespace pxsim {
             ["P3"],
             ["P4", "P5", "P6", "P7"],
             ["P8", "P9", "P10", "P11", "P12"],
-            ["P13", "P14", "P15", "P16"],
-            ["P19", "P20"],
+            ["P16"],
         ],
         gpioPinMap: {
             "P0": "P0",
@@ -36,6 +35,16 @@ namespace pxsim {
             "P19": "P19",
             "P20": "P20",
         },
+        spiPins: {
+            MOSI: "P15",
+            MISO: "P14",
+            SCK: "P13",
+        },
+        i2cPins: {
+            SDA: "P20",
+            SCL: "P19",
+        },
+        analogInPins: ["P0", "P1", "P2", "P3", "P10"],
         groundPins: ["GND"],
         threeVoltPins: ["+3v3"],
         attachPowerOnRight: true,
diff --git a/sim/microbit.ts b/sim/microbit.ts
index 1d5d2842..792907a5 100644
--- a/sim/microbit.ts
+++ b/sim/microbit.ts
@@ -147,7 +147,7 @@ namespace pxsim.visuals {
     const pin3Vmid = pins4onMids[13] + bigPinWidth / 2.0;
     const pinGNDmid = pins4onMids[pins4onMids.length - 1] + bigPinWidth / 2.0;
     const pinGND2mid = pinGNDmid + bigPinWidth / 2.0;
-    const pinMids = [pin0mid, pin1mid, pin2mid, pin3mid].concat(pins4onXs).concat([pinGNDmid, pin3Vmid, pinGND2mid]);
+    const pinMids = [pin0mid, pin1mid, pin2mid, pin3mid].concat(pins4onMids).concat([pinGNDmid, pin3Vmid, pinGND2mid]);
     const pinNames = [
         "P0", "P1", "P2", "P3", "P4", "P5", "P6", "P7", "P8", "P9", "P10",
         "P11", "P12", "P13", "P14", "P15", "P16", "P17", "P18", "P19", "P20",
diff --git a/sim/public/parts/.gitignore b/sim/public/parts/.gitignore
index d943933f..74a7a76e 100644
--- a/sim/public/parts/.gitignore
+++ b/sim/public/parts/.gitignore
@@ -2,4 +2,4 @@
 sparkfun-*
 raspberrypi-*
 arduino-*
-max6675*
\ No newline at end of file
+max6675*
diff --git a/sim/visuals/wiring.ts b/sim/visuals/wiring.ts
index 1f1248e0..d5a0b693 100644
--- a/sim/visuals/wiring.ts
+++ b/sim/visuals/wiring.ts
@@ -163,6 +163,41 @@ namespace pxsim.visuals {
         g.appendChild(el);
         return {el: g, x: x1 - strokeWidth, y: Math.min(y1, y2), w: w1 + strokeWidth * 2, h: h1 + h2};
     }
+    function mkSmallMBPinEnd(p: [number, number], top: boolean, clr: string): visuals.SVGElAndSize {
+        //HACK
+        //TODO: merge with mkOpenJumperEnd()
+        let k = visuals.PIN_DIST * 0.24;
+        let plasticLength = k * 4;
+        let plasticWidth = k * 1.2;
+        let metalLength = k * 10;
+        let metalWidth = k;
+        const strokeWidth = visuals.PIN_DIST / 4.0;
+        let [cx, cy] = p;
+        let yOffset = 10;
+        let o = top ? -1 : 1;
+        let g = svg.elt("g")
+
+        let el = svg.elt("rect");
+        let h1 = plasticLength;
+        let w1 = plasticWidth;
+        let x1 = cx - w1 / 2;
+        let y1 = cy + yOffset - (h1 / 2);
+        svg.hydrate(el, {x: x1, y: y1, width: w1, height: h1, rx: 0.5, ry: 0.5, class: "sim-bb-wire-end"});
+        (<any>el).style["stroke-width"] = `${strokeWidth}px`;
+
+        let el2 = svg.elt("rect");
+        let h2 = metalLength;
+        let w2 = metalWidth;
+        let cy2 = cy + yOffset + o * (h1 / 2 + h2 / 2);
+        let x2 = cx - w2 / 2;
+        let y2 = cy2 - (h2 / 2);
+        svg.hydrate(el2, {x: x2, y: y2, width: w2, height: h2, class: "sim-bb-wire-bare-end"});
+        (<any>el2).style["fill"] = `#bbb`;
+
+        g.appendChild(el2);
+        g.appendChild(el);
+        return {el: g, x: x1 - strokeWidth, y: Math.min(y1, y2), w: w1 + strokeWidth * 2, h: h1 + h2};
+    }
     function mkCrocEnd(p: [number, number], top: boolean, clr: string): SVGElAndSize {
         //TODO: merge with mkOpenJumperEnd()
         let k = visuals.PIN_DIST * 0.24;
@@ -325,7 +360,7 @@ namespace pxsim.visuals {
 
             return {endG: endG, end1: end1, end2: end2, wires: wires};
         }
-        private drawWireWithCrocs(pin1: Coord, pin2: Coord, color: string): Wire {
+        private drawWireWithCrocs(pin1: Coord, pin2: Coord, color: string, smallPin: boolean = false): Wire {
             //TODO: merge with drawWire()
             const PIN_Y_OFF = 40;
             const CROC_Y_OFF = -17;
@@ -349,7 +384,11 @@ namespace pxsim.visuals {
             pin2 = [x2, y2 + PIN_Y_OFF];//HACK
             [x2, y2] = pin2;
             let endCoord2: Coord = [x2, y2 + CROC_Y_OFF]
-            let end2AndSize = mkCrocEnd(endCoord2, true, color);
+            let end2AndSize: SVGElAndSize;
+            if (smallPin)
+                end2AndSize = mkSmallMBPinEnd(endCoord2, true, color);
+            else
+                end2AndSize = mkCrocEnd(endCoord2, true, color);
             let end2 = end2AndSize.el;
             let endG = <SVGGElement>svg.child(g, "g", {class: "sim-bb-wire-ends-g"});
             endG.appendChild(end1);
@@ -415,7 +454,13 @@ namespace pxsim.visuals {
             let endLoc = this.getLocCoord(end);
             let wireEls: Wire;
             if (withCrocs && end.type == "dalboard") {
-                wireEls = this.drawWireWithCrocs(startLoc, endLoc, color);
+                let boardPin = (<BoardLoc>end).pin;
+                if (boardPin == "P0" || boardPin == "P1" || boardPin == "P0" || boardPin == "GND" || boardPin == "+3v3" ) {
+                    //HACK
+                    wireEls = this.drawWireWithCrocs(startLoc, endLoc, color);
+                } else {
+                    wireEls = this.drawWireWithCrocs(startLoc, endLoc, color, true);
+                }
             } else {
                 wireEls = this.drawWire(startLoc, endLoc, color);
             }