Software - Basic Voltmeter
INTRO
This code builds on our Initial Test Software by adding a pushbutton press to change the Vrange. Again, even though we have NO analog prototype built yet, we can still write code and run a basic PRE-TEST with the Arduino UNO Board by itself.
Check out the Software Design overview.
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ARDUINO BASICS
Here's the fast track version of running a C program (sketch) on your Arduino Board.
- Open the Arduino IDE Software
https://www.arduino.cc/en/software - Connect UNO Board to your computer
https://docs.arduino.cc/hardware/uno-rev3/ - Select Board Name
Select UNO from drop down menu. - Download program (Right-Click "Save link as...")
DVM1_basic1.ino - Open program (sketch) in IDE
DVM1_basic1.ino - Click Compile Button
Generates executable code, checks for errors. - Click the Upload Button
Upoads compiled code into UNO and begins running. - Click the Serial Monitor
Window displays output from PrintSerial statement.
ARDUINO + ANALOG SCHEMATIC
The schematic shows the physical world that the code controls to implement our meter.
FLOW CHART
To out initial test flow, we've added the blocks to Read Pushbutton and change Vrange.
CODE STRATEGY / THEORY
A pushbutton as digital input requires only one additional component, a
pullup resistor.
The two states can be described as
SW Vdin Digital
Open 5V logic 1
Closed 0V logic 0
You read the button state every trip through the loop() function (or 0.25s) using digitalRead(Dx). The present and last reading are stored in variables
- buttonState
- lastButtonState.
Although Normally Open, a press of the button causes a logic transition from 1 to 0. You can easily detect this change with the conditional statement
- if( lastButtonState == 1 && buttonState == 0 ) {
toggle voltage range
}
Arduino Pin usage
- A0 Analog Input - Voltage Reading
- D12 Digital Output - SW1 R Divider
- D13 Digital Output - SW2 R Divider
- D8 Digital Input - Pushbutton for Vrange
THE CODE
Again, this section describes the added function of the pushbutton to our initial test code. The goal is fairly straighforward to create some reasonable code. However, I'm open to any suggestions from those with more Software experience.
Declarations
The variable declararions occur before the setup() function.
Setup()
This code excecutes once in the Arduino Sketch. The digital bit D11 has been added as an input to read the state of the Pushbutton.
Loop()
This code runs continuously. Here's the added code that looks for a 1 to 0 transition on the pushbutton state. See comments in gray for description.
PRE-TEST
What can we test even though the analog circuitry has NOT been prototyped? Yes you can jumper digital input D11 to GND or leave OPEN for a digital state of 0 or 1.
- Leave D11 unconnected.
- Open program (sketch)
DVM1_basic1.ino - Click the Upload Button
Also Compiles before uploading. - Click the Serial Monitor
- Do you see variable buttonState = 1 and Vrange = 0 (default values)?
if Yes, then celebrate the success!
if NO, then check code and jumper. - Connect wire jumper from D11 to GND
- As you connect D11 to GND, do you see buttonState transition from 1
to 0 and Vrange = 1?
if Yes, then celebrate the success!
if NO, then check code and jumper. - Repeatedly remove and reconnect the D11 wire jumper to GND. Verify that the Vrange variable toggles between 0 and 1.
DESIGN IMPROVEMENT
The phase of software coding led to design improvement! While looking at Arduino code examples and documentation, I noticed an option for the pinMode() statement for an internal pull-up resistor option.
- pinMode( pin, mode)
- mode parameter: INPUT, OUTPUT, or INPUT_PULLUP (20k internal resistor to +5V)
- As a result, R5 can be removed from the design opting for the internal resistor instead!
NEXT UP
Congratulations for travelling this far, the basic voltmeter code is complete! However, in order to fully test it, we'll need to start constructing the actual prototype..
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