This is a different kind of tuner graphic that displays a Smith Chart dynamically as you tune the antenna matching network.
You can view the Hardware Diagrams  below:
 

A video demonstrating how it works can be viewed HERE.

The Arduino Source Code can be viewed HERE.

A 360 degree phase detection is needed for this project.  I found the following process using two AD8302 modules.  This allows a complete 360 degree calculation which is needed in a Smith Chart graphic display.  The following pictures show the hardware used in this project.
 
 

Here is a picture of the tuner front with 40m selected and the MFJ-989C slightly tuned off resonance..

MFJ-989C Tuner with Smith Chart.
 

The picture below is a closeup of just the SmithChart.  When perfectly tuned with the MFJ-989, the dot is in the middle of the chart.  The impedance and the SWR are updated every 5 seconds as the MFJ tuner is adjusted.

Close up.

26-dB Attenuator Open.

26-dB Attenuator Assembled.
 
 

Smith Chart Display Front View.
 
 

Smith Chart Display Back View.
 
 

Smith Chart Display Top View.

This device needs sampled Current and Voltage waveforms in order to do the calculations.  Below is the Coupler Schematic.

Coupler Schematic.
 

Coupler Load View.

Coupler Top View.
 

Coupler Transmitter View.

The coupler must have the Current and Voltage waveforms in phase and equal amplitude when terminated in 50 ohms.  The picture below confirms that.
 

Current and Voltage in Phase and Equal Amplitude when terminated in 50 ohms.