diff --git a/package-lock.json b/package-lock.json
index 1e314732..ef50c0d9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,17 +1,18 @@
 {
   "name": "honeycomb",
-  "version": "3.4.0",
+  "version": "3.4.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "honeycomb",
-      "version": "3.4.0",
+      "version": "3.4.1",
       "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
         "@fortawesome/fontawesome-free": "^6.4.2",
         "@jspsych/plugin-audio-keyboard-response": "^1.1.3",
+        "@jspsych/plugin-call-function": "^1.1.0",
         "@jspsych/plugin-fullscreen": "^1.2.0",
         "@jspsych/plugin-html-button-response": "^1.1.1",
         "@jspsych/plugin-html-keyboard-response": "^1.1.1",
@@ -6510,6 +6511,14 @@
         "jspsych": ">=7.1.0"
       }
     },
+    "node_modules/@jspsych/plugin-call-function": {
+      "version": "1.1.3",
+      "resolved": "https://registry.npmjs.org/@jspsych/plugin-call-function/-/plugin-call-function-1.1.3.tgz",
+      "integrity": "sha512-3+sIav7+e3Ie/jNZQAZZL3M0uvZT69fvpP3JBUhnH8eB23sLbCPEUHbGj9C7gdslJ9gjrJo3rMdgTRuWC0w3MA==",
+      "peerDependencies": {
+        "jspsych": ">=7.1.0"
+      }
+    },
     "node_modules/@jspsych/plugin-fullscreen": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/@jspsych/plugin-fullscreen/-/plugin-fullscreen-1.2.1.tgz",
diff --git a/package.json b/package.json
index 7a659e62..ee5f0024 100644
--- a/package.json
+++ b/package.json
@@ -16,6 +16,7 @@
   "dependencies": {
     "@fortawesome/fontawesome-free": "^6.4.2",
     "@jspsych/plugin-audio-keyboard-response": "^1.1.3",
+    "@jspsych/plugin-call-function": "^1.1.0",
     "@jspsych/plugin-fullscreen": "^1.2.0",
     "@jspsych/plugin-html-button-response": "^1.1.1",
     "@jspsych/plugin-html-keyboard-response": "^1.1.1",
diff --git a/src/experiment/honeycomb.js b/src/experiment/honeycomb.js
index 28a6bfaf..dc8c15ff 100644
--- a/src/experiment/honeycomb.js
+++ b/src/experiment/honeycomb.js
@@ -53,8 +53,8 @@ export function buildHoneycombTimeline(jsPsych) {
 
   const timeline = [
     startProcedure,
-    countdownTrial,
     preloadTrial,
+    countdownTrial,
     instructionsTrial,
     honeycombProcedure,
     debriefTrial,
diff --git a/src/experiment/procedures/startProcedure.js b/src/experiment/procedures/startProcedure.js
index 6483ebd7..8d1465f4 100644
--- a/src/experiment/procedures/startProcedure.js
+++ b/src/experiment/procedures/startProcedure.js
@@ -6,6 +6,7 @@ import { holdUpMarkerTrial } from "../trials/holdUpMarker";
 import { nameTrial } from "../trials/name";
 import { initPhotodiodeTrial } from "../trials/initPhotodiode";
 import { introductionTrial } from "../trials/introduction";
+import { buildCallFunctionTrial } from "../trials/callFunction";
 
 /**
  * Builds the block of trials needed to start and setup the experiment
@@ -24,6 +25,11 @@ export function buildStartProcedure(jsPsych) {
   // Conditionally add the photodiode setup trials
   if (config.USE_PHOTODIODE) {
     procedure.push(holdUpMarkerTrial);
+    procedure.push(
+      buildCallFunctionTrial(() => {
+        window.electronAPI.checkSerialPort();
+      })
+    );
     procedure.push(initPhotodiodeTrial);
   }
 
diff --git a/src/experiment/trials/callFunction.js b/src/experiment/trials/callFunction.js
new file mode 100644
index 00000000..04820266
--- /dev/null
+++ b/src/experiment/trials/callFunction.js
@@ -0,0 +1,14 @@
+import callFunction from "@jspsych/plugin-call-function";
+
+/**
+ * Trial to execute the callback function passed in
+ *
+ * @param {function} func callback function to execute
+ * @returns JS object as a trial
+ */
+export function buildCallFunctionTrial(func) {
+  return {
+    type: callFunction,
+    func: func,
+  };
+}
diff --git a/src/experiment/trials/holdUpMarker.js b/src/experiment/trials/holdUpMarker.js
index 0f384fc9..6a1848ea 100644
--- a/src/experiment/trials/holdUpMarker.js
+++ b/src/experiment/trials/holdUpMarker.js
@@ -1,32 +1,14 @@
 import htmlButtonResponse from "@jspsych/plugin-html-button-response";
-
-import { config, LANGUAGE } from "../../config/main";
-import { eventCodes } from "../../config/trigger";
-import { pdSpotEncode, photodiodeGhostBox } from "../../lib/markup/photodiode";
-import { div, h1, p } from "../../lib/markup/tags";
+import { LANGUAGE } from "../../config/main";
+import { h1 } from "../../lib/markup/tags";
+import { photodiodeGhostBox } from "../../lib/markup/photodiode";
 
 // TODO @brown-ccv #330: Custom extension for EEG - this is initializeTriggerBox
 // TODO @brown-ccv #330: Need to ping the serial part - this isn't doing anything yet
-// TODO @brown-ccv: Prevent user from pressing continue until pdSpotEncode finishes (need to use jsPsych.pluginAPI.setTimeout)
 export const holdUpMarkerTrial = {
   type: htmlButtonResponse,
-  stimulus: function () {
-    const eventMarkerMarkup = h1(LANGUAGE.trials.eventMarker.connected, {
-      style: "color: green;",
-    });
-    return div(eventMarkerMarkup);
-  },
-  prompt: function () {
-    let holdUpMarkerPrompt = p(LANGUAGE.trials.holdUpMarker);
-
-    // Conditionally add the photodiodeGhostBox
-    if (config.USE_PHOTODIODE) holdUpMarkerPrompt += photodiodeGhostBox;
-
-    return holdUpMarkerPrompt;
-  },
+  stimulus:
+    h1(LANGUAGE.trials.holdUpMarker) +
+    photodiodeGhostBox,
   choices: [LANGUAGE.prompts.continue.button],
-  on_load: function () {
-    // Conditionally flash the photodiode when the trial first loads
-    if (config.USE_PHOTODIODE) pdSpotEncode(eventCodes.test_connect);
-  },
 };