From 8c49dea47485c0d9f31dd9793d7822a3fd3e58b4 Mon Sep 17 00:00:00 2001
From: Peter Stockings <pstockings@jadeworld.com>
Date: Thu, 26 Jan 2023 12:40:38 +1100
Subject: [PATCH] Add delay after connecting to BLE device and start
 notifications before adding on characteristic change event listener

---
 static/js/BLE.js | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/static/js/BLE.js b/static/js/BLE.js
index c73c104..baae75a 100644
--- a/static/js/BLE.js
+++ b/static/js/BLE.js
@@ -1,3 +1,7 @@
+function delay(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
 async function connect(props) {
   const device = await navigator.bluetooth.requestDevice({
     filters: [{ services: ["cycling_speed_and_cadence"] }],
@@ -5,15 +9,19 @@ async function connect(props) {
   });
   console.log(`%c\n👩🏼‍⚕️`, "font-size: 82px;", "Starting CSC...\n\n");
   const server = await device.gatt.connect();
+  await delay(500);
+  console.log("Getting Service...");
   const service = await server.getPrimaryService("cycling_speed_and_cadence");
-  const char = await service.getCharacteristic("csc_measurement");
-  char.oncharacteristicvaluechanged = props.onChange;
-  char.startNotifications();
-  return char;
+  console.log("Getting Characteristic...");
+  const characteristic = await service.getCharacteristic("csc_measurement");
+  await characteristic.startNotifications();
+  console.log("> Notifications started");
+  characteristic.addEventListener("characteristicvaluechanged", props.onChange);
 }
 
 function parseCSC(e) {
-  const flags = e.target.value.getUint8(0, true);
+  const value = e.target.value;
+  const flags = value.getUint8(0, true);
   const hasWheel = !!(flags & 0x01);
   const hasCrank = !!(flags & 0x02);
   let index = 1;