Low frequency oscilloscope for Android using PIC16F1459. The input is to pin 13, pin 14 is comperator input. This scope is for low frequencies, up to 5KHz. The sampling is done by the PIC ADC in a speed of about 20K sampling per sec. The software for Android is in B4A basic for android. The pic takes 62 samples of input to create one screen. For lower frequency a delay for each sample gives slower sweep. The Android app set to USB CDC class.To install the app on Android device place the APK file in the device and open the file. Load code to the Arduino and connect it via OTG cable. OTG (On The Go) is the cable that is used to connect USB devices (other than charger or PC) to phones or tablets. Input is DC or AC not acceding 5V. The Analogue Comperator of the PIC detects zero crossing of input signal, it triggers start of sampling a frame when signal is rising.
Software for PIC and app for Android can be downloaded from GitHub: https://github.com/projects22/PIC16F1459-Oscilloscope
Included code for the app, if you wish to change it download free IDE from: https://www.b4x.com