In the previous post I described the entire system architecture.  In this post, I am going to describe the Arduino shield that I unfortunately call “Elkhorn Creek Water Level 1.1”.  It is unfortunate because in version 1.0 I made a really stupid error which ruined the first run of printed circuit boards.  You can read more about how I made the error and what I am doing in the future in the post Creek Board 1.0 RCCA.

To make this system work I need to be able to interface the PSoC4200 with two sensors:

Both of these sensors are subject to environmental noise so they both have capacitive or RC filters connected to them.  I originally built a prototype of this board using a proto board.  However, it was a PITA because the wires would come loose and the system would stop working.


So I decided to make a real PCB.  To do the design, I used the Eagle 7.2 PCB editor as it seemed like it had the most support from the maker community.  The schematic for the system is fairly simple.  It has

  • Pressure Sensor
    • X1: A Molex Microfit 3.0 Connector to attach the two wires from the pressure sensor
    • R1: A 51.1 Ohm resistor to group to convert the 4-20mA –>  0.204mV to 1.022V
    • C1/R2: A low pass filter
    • TVS1: A ESD diode to clamp any ESD event to ground to prevent it from blowing up the PSoC4A or the Sensor
  • Temperature Sensor
    • TMP36: A sensor that turns temperature into a voltage.  The equation for temperature is T=0.5V+10mV/degreeC.  For 25 degrees C the Voltage = 750mV
    • C2 + C3: Two decoupling capacitors to filter power supply noise
  • Arduino Interface
    • A standard Arduino interface set of pins + the additional Cypress CY8CKIT-042 pins.  I only used the A0 and A1 pins for signals and the Vin pin (which is 12v) to drive the current loop
  • Measurement Test Points
    • Keystone 5000 test points.  These test points are a little loop of wire that sticks up from the surface of the PCB to make  it easy to probe a voltage with your DMM.  5000_sml

Here is the final Eagle Schematic for the board.


And the layout:CreekBoard2.0Layout

Once I completed the layout I sent the board to OSH Park to be manufactured.  I have shared the project on their website.  OSH Park is an excellent company that is easy to do business with.  They charged me $22.55 for three of the boards.  The fit and finish of the boards is very nice.  Here is the board:


Here is the assembled board:



I have posted all of the project files at github.  You can “git” them from  The Eagle project is in the CreekBoard directory.

Index Description
The Creek: IOT for the Elkhorn Creek Introduction
The Creek: Solution Architecture 1.0 Overall architecture
The Creek: Creek Board 1.1 Eagle layout of the board
The Creek: Creek Board 1.0 – RCCA A discussion of the errors in the 1.0 board
The Creek: CYPI, a Raspberry Pi to Arduino Bridge PSoC4 <--> Raspberry Pi Bridge Board
The Creek: PSoC4 Creator Schematic and Firmware Firmware to interface with the temperature and pressure sensors
The Creek: Testing the Firmware Using tools to verify that the PSoC 4 Firmware is working correctly
The Creek: Testing the Bootloader Make sure that you can load new firmware into the PSoC
The Creek: Software Architecture All of the Raspberry Pi software connections
The Creek: Install MySql Instruction to configure MySql
The Creek: Install Tomcat Instruction to configure Tomcat JSP Server
The Creek: Data Collection Java (Part 1) The Java program that reads the I2C and saves it in the database
The Creek: Data Collection Java (Part 2) The Java program that reads the I2C and saves it in the database
The Creek: Create the Chart with JFreeChart Using open source Java charting software to create plots of the Creek Depth
The Creek: Flood Event Data Processor A batch program to create analyze the database and create a table of flood events
The Creek: Flood Event Web Page A batch program to create the flood event web page
The Creek: Creek Server 1.1 Updates to all of the back off server programs to integrate charts
The Creek: JSP Web Page for The JSP program to make the table and display the website
The Creek: Raspberry Pi Clock Stretching Sorting out a bug in the system having to do with the Broadcomm Raspberry Pi Master not functioning well with clock stretching
The Creek: Creek Server 1.2 Caching the web pages to make them faster

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