web serial cleanup (#928)

* updated ticks

* fix enable and compile

* add debug mode

* don't try to change UI while downloading

* cleanup

* don't double open

* use cu

* add delay before reconnecting

* support for 200 ragne in field turn ratio

* updated docs

* fix docs

editor/extension.ts

@@ -7,6 +7,13 @@ let bluetoothDialogShown = false;
 pxt.editor.initExtensionsAsync = function (opts: pxt.editor.ExtensionOptions): Promise<pxt.editor.ExtensionResult> {
     const projectView = opts.projectView;
     pxt.debug('loading pxt-ev3 target extensions...')
+
+    function enableWebSerialAndCompileAsync() {
+        return enableWebSerialAsync()
+        .then(() => Promise.delay(500))
+        .then(() => projectView.compile());
+    }
+
     const res: pxt.editor.ExtensionResult = {
         deployCoreAsync,
         showUploadInstructionsAsync: (fn: string, url: string, confirmAsync: (options: any) => Promise<number>) => {
@@ -84,7 +91,7 @@ pxt.editor.initExtensionsAsync = function (opts: pxt.editor.ExtensionOptions): P
                     onclick: () => {
                         pxt.tickEvent("bluetooth.enable");
                         if (bluetoothDialogShown) {
-                            enableWebSerialAsync().done();
+                            enableWebSerialAndCompileAsync().done();
                         } else {
                             bluetoothDialogShown = true;
                             confirmAsync({
@@ -99,13 +106,13 @@ pxt.editor.initExtensionsAsync = function (opts: pxt.editor.ExtensionOptions): P
                                 }],
                                 htmlBody: `<p>
 ${lf("You will be prompted to select a serial port.")}
-${pxt.BrowserUtils.isWindows() ? lf("Look for 'Standard Serial over Bluetooth link'.") : lf("Loop for 'tty.EV3-SerialPort' or 'cu.EV3-SerialPort'")}
+${pxt.BrowserUtils.isWindows() 
+    ? lf("Look for 'Standard Serial over Bluetooth link'.") 
+    : lf("Loop for 'cu.EV3-SerialPort'.")}
 ${lf("If you have paired multiple EV3, you might have to try out multiple ports until you find the correct one.")}
 </p>
 `
-                            }).then(() => enableWebSerialAsync())
-                                .then(() => Promise.delay(500))
-                                .then(() => projectView.compile())
+                            }).then(() => enableWebSerialAndCompileAsync())
                         }
                     }
                 } : undefined, downloadAgain ? {