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HOME   Technical Tips

ANDROID ARDUINO OSCILLOSCOPE

Low frequency oscilloscope for Android using Arduino Uno or Nano. The input is to pin A0 of the Arduino which connected to Android device via USB OTG cable.This scope is for low frequencies, up to 5KHz. The sampling is done by the Arduino ADC in a speed of about 10K sampling per sec. The Arduino software is mostly in Atmel code in purpose to get wider bandwidth. The software for Android is in B4A basic for android.The Arduino takes 60 samples of input, 60 samples create one screen. For lower frequency a delay of 1mS for each sample gives slower sweep.To install the app on Android device place the APK file in the device, when you open the file it ask if you want it installed. 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 Comparator of the mc (pins 6, 7)  is used to detect zero crossing of input signal, it triggers start of sampling a frame when signal is rising.

Software for Arduion and app for Android can be downloaded from GitHub. Included code for the app, if you wish to change it download free IDE from:   https://www.b4x.com/
You are free to use the circuit diagram and the software with no limitations.

ANDROID PIC16F1459 OSCILLOSCOPE

 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 60K 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 pic 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. Included code for the app, if you wish to change it download free IDE from: https://www.b4x.com/

ANDROID MICROPHONE OSCILLOSCOPE

Oscilloscope app for Android with input to the microphone socket. Low frequency oscilloscope no need for external active components. Microphone input is 0.5V max, AC signals only, the input is connected to the device ADC via a capacitor. The bandwidth is about 30 to 5000 Hz, the cap coupling causes the lower limit, the slow basic program and the device ADC define the upper limit. The sampling rate is 44.1Ksps Arduino takes 60 samples of input, 60 samples create one screen, for Y x 10 every tenth sample is taken.
App is in B4A (basic for Android), To modify the app to your needs you can download the free IDE from https://www.b4x.com/ To install the app download APK file and open it in your device. Input is to the microphone socket. Input voltage divider allows signals of 5V P-P. Alternative way is to use an existing headset and connect the input in place of the mic. When no input plugged in the scope shows the signal from the internal mic. The 18 ohm resistors simulate speakers, it lets the device switch to external mic.

 
   

Circuit Description
See also Technical Tips

100K resistors set input to 2.5V to run signal at center of screen.
Arduino pin A0 and PIC pin 13 are inputs for the signal.
Arduino pins 6, 7 and PIC pin 14 are inputs of the analogue comparator, the comparator detects zero crossing and triggers start of frame.  

 

Circuit Description
See also Technical Tips

100K, 10K resistors are voltage divider to set the input to 5 Vp-p
18 ohm resistors are to simulate speakers, it lets Android to switch to external mic.



           



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