Arduino for Beginners, Now With Data Plotting, Controlled by Android, No Coding Required, No Soldering Required.

Introduction

This instructable shows you how you can read and write the digital pins on your Arduino Uno and read values from the analog pins all controlled from your Android mobile without doing any coding. This entire project is plug and play. No soldering is required so it is suitable for complete beginners.

Once you have experimented with turning outputs on and off from your mobile and reading voltages, a later instructable will go on to guide you through some simple code examples you can use to build your own projects controlled from your Android mobile. None of these projects require any Andriod programming. The same pfodApp is used for all the examples. The menus on your mobile are completely controlled by simple strings in your Arduino code.

Quick Start

Above is photo of the components you need, in addition to a computer with a USB port. This is the Uno Starter parts list. The cost of parts (excluding the mobile and computer) is approximately US50.00 + shipping

Now that you have constructed your Android Controlled Uno you can try setting pins as inputs and outputs. By default the UnoStarter sketch sets all digital pins as inputs with pullups, except D0, D1 and D2 which are used by the Bluetooth Sheild and cannot be modified.

This project uses 330ohm resistors as connecting wires. Using 330ohm resistors as connection wires protects against shorting out any of the pins. However the wire on these resistors is very thin and you may need to push them to make contact in the header sockets.

Reading a Digital Input.

Using one of the 330ohm resistors connect D3 to Gnd. The display of the D3 on you mobile will change from HIGH to LOW. The pfodApp on your mobile re-request this screen about once a second.

Driving a Digital Output

Move the resistor connection so that D3 is connected to D7. Then click on D7 on you mobile and configure that pin to be OUTPUT LOW. D3 will update to show INPUT LOW.

Driving a Led

You need to connect a resistor to the Led to limit the current. Take the longest leg of the Led (the positive leg / anode)  and bend it up and twist one end of a 330ohm resistor around it. Then plug the remaining leg of the Led into one of the Gnd pins and plug the other end of the resistor into D3.

Now when you configure D3 as OUTPUT HIGH the Led lights. Configuring OUTPUT LOW turns it off. Configuring INPUT with Pullup will turn the Led on weakly because the 20K pullup resistor connects 5V to the D3 input and so supplies some current to the Led.

Varying the Led Brightness (PWM)

The final Digital Pin example is driving the Led with a PWM signal. PWM (pulse width modulation, see http://arduino.cc/en/Tutorial/PWM) turns the output on and off about 500 times a second. In each cycle of On and Off the percentage of time the Led is ON can be set by a slider on the mobile.

Click on D3 and from the configuration screen choose PWM. Only those Digital Pins marked with * have PWM capabilities. When PWM is selected a slider is displayed which lets you select the percentage the Led is On during each cycle. There are about 500 cycles per sec which is to fast for you to see each on/off switch. Your eye averages the result, so as you increase the % on time (the duty cycle), the Led appears to be brighter.

Measuring a Voltage

The AtoD inputs allow you to measure a voltage. The voltage applied to the AtoD input MUST NOT be greater the 5V. The AtoD compares the voltage on its input pin to the reference voltage and returns a number between 0 and 1023, where 1023 corresponds to the Reference voltage supplied to the AtoD. There are 3 reference voltages available, 5V, 1.1V and the voltage applied to the AREF pin. The 1.1V reference is not very accurate if you want to use it you will need to calibrate the result using a voltmeter. The 5V reference is accurate within a couple of %.

To measure a voltage, open the Analog Pin screen and click A0 to open its configuration screen. Choose the 5V reference. Then connect a 330ohm resistor between A0 and the 3.3V pin on the next header. The Analog screen will now show the measured volts. The pfodApp on your mobile re-request this screen about once a second.

The measurement will not be exactly 3.3V because of inaccuracies in both the 5V reference and the voltage on the 3.3V pin and the electrical noise on the A0 pin.

One of the features of the pfod message specification is that when displaying a number in a menu, you can tell the pfodApp the apply a scale and offset as well as a units. When the 5V reference is selected and the UnoStarter sketch sends the Analog menu to the pfodApp on your mobile, it includes a units of “ V” and a scale factor of 0.0048876. When the AtoD converts the 3.3V input using a 5V reference, it will return a reading of 681 (681/1023 == 3.3/5). On your mobile the 681 counts is multiplied by the scale factor 0.0048876 = 3.328, so mobile will display 3.328 plus the units “ V”.

As well as setting the Digital I/O and enabling the AtoD inputs, you can also plot the values. About once per sec, the Uno pfodDevice sends raw data messages to the pfodApp containing the latest readings of the digital pins and the reading of the AtoD inputs, if enabled. You can view these reading via the Raw Data screen (accessed from your mobile's menu button).

The pfodApp automatically starts saving this data to a file on your mobile when you view of plot raw data. You can later download this file to your computer (see the pfodAppForAndroidGettingStarted.pdf for the details).

Plotting the Digital Inputs
The Arduino code running on the Uno also provides two menu items to plot the raw data.

Choose “Plot Digital Inputs” to see the state of the digital pins. If set as an input the plot will update on each transition. If set as an output it will show the current state (high/low). If the digital pin is set as a PWM output then the plot will just sample the pin once per sec. Try connecting a pin set as PWM output to one of the other pins set as an input. The plot for the input pin will rapidly change as the it driven by the PWM output.

Plotting the Analog Inputs
To see a plot of an Analog input you have to first enable one of the inputs, then connect a voltage to it. Try setting A3 with a 5V reference and then connecting a PWM digital output to it (twist 2 resistors together to bridge across the board). The sketch will sample the analog input once a sec and return the values for plotting.

To see the messages that are being sent back and forth between the pfodApp on you mobile and the pfodDevice (your Uno), open the Debug View from your mobile's menu. Above are the messages for the 3.3V measurement on A0.

< are message from the mobile to the Uno and
> are messages from the Uno to the mobile.

The {a} from pfodApp requests the Analog pins screen. The pfodDevice, the UnoStarter sketch responds with the data for this menu.
The {. at the start of the message specifies a menu screen. The “Analog Inputs” is the title of the screen. The '1000 says re-request this menu again after 1 sec (1000mS).
The | starts a menu item. The “aa” is the command associated with this menu item and the text after the ~ is the text to display. There are a number of versions of the menu item from plain text e.g. “A2 Disabled” to scaled results with units as in “A0`681~ V~0.0048876” to slider menu items. See the pfod Specification for all the details and examples.

Next Steps

To learn more about coding Arduino see http://arduino.cc/en/Tutorial/HomePage
For more pfodDevice projects, like Android controlled garage door openers, see www.pfod.com.au
If you want to continue with controlling things with Arduino you will want to either purchase a bread board and base or preferably learn to solder.

The next instructable, How to switch an Arduino output on and off from your Android mobile,  provides some simple examples you can use as a basis for your own projects. All without any Android programming.  That instructable also covers debugging your sketch from your mobile.

In the mean time check out the existing instructables using pfodApp and the pfod Specification and the projects on www.pfod.com.au