JavaScript Oscilloscope

 Objective

This is an example how to use JavaScript and Websockets to create an online oscilloscope

  1. The PIC32MZ2048EFH144 on the Ethernet Starter Kit is acting as a webserver
  2. In the 512 kB MPFS file system of the PIC32 flash memory, all JavaScript libraries used (~250 kB), are stored compressed.
  3. The software is based on the Harmony 1.07.01 TCPIP example project "web_net_server_nvm_mpfs"
  4. The ADC channel 4 is set up to sample at 2 MHz and 12-Bit. Every 100 ms a measurement is triggered and the DMA collects 1024 sample values in an array
  5. In the array, a trigger condition is searched to get a stable image
  6. From the trigger condition, 100 samples are sent to the web browser (client) which displays the value

Below are the necessary connections:

SK.png

In a terminal window you have direct command line access:

terminal.jpg

Use a signal generator to apply a signal to pin 15 (RB4/AN4):

signal-3.jpg

Use a web browser and enter the URL: 192.168.100.115 (as long as it is connected directly):
Click on "Realtime Websocket Stream"

startpage.jpg

Enter the correct IP address, and click on "Connect"

ip_address.jpg

You should see the signal measured at RB4/AN4 on pin 15 of the board header

triangle.jpg

Note that when you compare it with a real scope it looks very much the same :-)

real_scope.jpg

Below is a screencast video. Although it's from an earlier version it still explains the principles:
Online Oscilloscope with Websockets

 Materials

Hardware Tools (Optional)

Tool About Purchase
PIC32MZ-EF-50px.png
PIC32MZ Embedded Connectivity with FPU
Starter Kit

Software Tools

Tool About Installers
Installation
Instructions
Windows Linux Mac OSX
MPLAB® X
Integrated Development Environment
MPLAB® XC32
C/C++ Compiler
MPLAB® Harmony
Integrated Software Framework

Exercise Files

File Download
Installation
Instructions
Windows Linux Mac OSX
Project and Source Files

 Procedure

There are two ways to connect the Ethernet Starter Kit (ESKT):

1

Connect to a network switch. The board will attempt to obtain an IP from a DHCP server.
Find the IP adress with the tcpip_discoverer.jar utility from:
c:\microchip\harmony\v1_07_01\utilities\tcpip_discoverer\.

2

Connect the ESKT directly to a PC and set the PC to a fixed IP adress, for example 192.168.100.120

Author:

Martin Rupert
Microchip Technology Inc.

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