I'm trying to send data from an Arduino nano to an app made in App Inventor using a HC-05 bluetooth module. From what I've seen in this tutorial (https://www.youtube.com/watch?v=j4Raxn5Fqxc&t=295s) you need to pair the clock in your app with the delay used in the arduino sketch. The idea behind all of this is to receive data form an ECG signal to visualize it on the phone. To test the app I use the voltage divider with a potentiometer as in the video, but I'm using a delay of 4 ms (+1 ms used to send the data byte) to obtain a sampling freq. of 200 Hz and my app clock is set to 5 ms. I only get noise and when I change the value with the potentiometer the app doesn't respond accordingly; i'm not sure if the delay is too small or if there is something wrong with the synchronization.