Furlough 40 Goes Color - Arduino SSB TFT Display Module

I wanted to liven up the display module for my F40 - the 4x20 LCD display is certainly functional, but decidedly industrial in look.  I have gotten quite fond of the color display on my uBitx, so I decided to build a color display module for the F40.   I opted for a color TFT for the display since they are ubiquitous, inexpensive and there are many good Arduino libraries that make programming a snap.  Uber Elmer N6QW, Pete Juliano graciously shared with me the sketches he had written for various color TFT projects and I downloaded and also evaluated sketches from several other hams. Not quite finding what I wanted, I decided to write my own sketch.

I should let you know that I'm a relatively young ham (60 years young, but licensed only two years ago), but I am a very old software guy (still 60,  but have been a professional software engineer and executive for 40 years).  So, when I started looking at source code for Arduino sketches that were written by amazing hams with no formal software training I knew I had to dive in.

My design goals for the project were the following:

• The code must follow sound software engineering principles throughout.
• It must be modular and reusable.  To be easily reusable the code most not be dependent on any particular hardware design.  You should be able to drop it in to any Arduino based radio control program with minimal effort.
• It must have a small memory foot print and not use up much of the Arduino's precious dynamic RAM.
• It must be fast and not tax the Arduino microcontroller- we want to save its CPU cycles for control of the rig. 
  
• It must use standard Arduino display libraries and be relatively hardware independent - easy to port to a different display or microcontroller.
  
• It must be easily reconfigurable - you should not have to change code to make simple user interface changes like screen colors and font sizes.
• It must provide the basic display functions for a dual VFO SSB rig - and that means dual VFO display, active VFO indicator and LSB/USB indicator.
•  It must be easy to add new display elements - including an S meter and other similar displays.
• And last, the code must be easy for a non-professional coder to understand and work on.  No tricks or fancy code footowork.
  

So, over the long memorial day weekend I wrote and tested the KK4DAS SSB TFT Display.

A quick note if you are interested in building this.  This is not a complete radio control sketch - it is only the display module. Over the coming weeks I will publish additional modules that will implement a complete SSB transceiver controller.  But for now, all you need is an Arduino and a color TFT, and possibly some level shifters.  The Arduino nano uses 5V logic but the TFT needs 3.5V logic so the level shifters are used to take care of that.  You'll also need to install the Arduino IDE and load the two required libraries.

Here are some of the details:

Features

• Basic radio display panel for an SSB transsceiver
• Designed for a 320x240 Color TFT (non touch)
• Tested with an ILI9341 display

Requires the following libararies

• Adafruit_GFX
• Adafruit_ILI9341

Implements a basic SSB display console with the following features

 Dual VFO A/B
 Mode indicator  SSB/LSB
 Tx/Rx ndicator
 TuningStep Inidicator
 S Meter
 Banner including Call sign

 Fully customizable. Fast display makins use of minimal resources./
 Room is left on the screen for additional features
 There is room on the screen for another row of features
 
 Easily change colors, font sizes and layout

Default Screeen Layout

  ____________________________________
  |       A 7.200.000 LSB             | -- VFO A/B indicator, Active VFO Freq, LSB/USB inidicator
  |      Rx 7.048.000 100K            | -- Rx/Tx indicator, Alternate VFO Freq, Tuning Increment
  |                                   | 
  |      S |_|_|_|_|_|_|_|_|_|_|_|_|  | -- S Meter
  |         1   3   5   7   9         |
  |                                   |
  |        AGC   SPL   RIT            | -- (Planned) AGC on/of, Split On/Off,  RIT On/OFF
  |                                   |                                        
  |     Ver   Rig Name   Call         |
  |___________________________________|

This module provides the following radio console display functions:

• displaySetup - initialize the display and displays the startup values - call once from your setup function
• displayBanner - Displays a text banner across the bottom of the screen
• displayActVFO - Displays the frequency of the Active VFO
• displayAltVFO - Displays the frequency of the Alternate VFO
• displayVFOAB - Displays the indicator which VFO is active (A or B)
• displayTxRx - Displays whether the rig is in (Tx or Rx)
• displayMode - Displays the which sideband is selected (LSB or USB)
• displayIncr - Displays the tuning increment (10, 100, 1K 10K, 100K, 1M)
• displaySMeter - Displays the S Meter (1-9 are gray, +10 +20 and +30 are red

This module also provides the following general purpose display functions:

• displayClearScreen - fills the screen with the selected backgrond color
• displayPrintat - prints text or nubmers on the screen at a specific location
• displayDrawBoundingBox - draw a box on the screen and fills it with a background color
• displayDrawTextBox - displays text inside a boundig box

Design notes and how to use the code

NOTE TO BUILDERS

This is not a complete radio control sketch. It is the Display software only. In the spirit of modular design it is stand-alone and not dependent on using an SI-5351 or any other specific hardware, or on my particular hardware selection of switches, buttons and knobs. The demonstration sketch shows how to update the display, but you need to provide the code to determine what the actual values should be. You will likely need other libraries like the Si5351 and a Rotary encoder library aside from the GFX and the ILI9341.

DESIGN PRINCIPLES

Good software design principles are to use as few hard-coded numbers as possible. Wherever possible I have used #defines for any number that will be used more than one place in the code. For example #define DSP_VFO_ACT_X 60 defines the X coordinate (how far from the left of the screen) of the Active VFO frequency display. You will see multiple references to DSP_VFO_ACT_X throughout the code, but I never use the hardcoded number 60 again. Change it once – and it is changed throughout.

Taking the S-Meter as an example:

To update the S-Meter display you make a call to displaySMeter(n); where n is an integer from 1 to 12 (representing S1-9, +10, +20 +30). Your sketch will need a way of monitoring signal strength (an analog input pin on the Arduino attached to an appropriate place on your rig) and converting it to the logarithmic S scale.

SCREEN COORDINATES

Coordinates work differently on displays than a typical graph where the origin 0,0 is in the middle abd positive and negative values move you away from the origin. For displays 0,0, the origin, is always upper left hand corner of the display and you only use positive numbers for the coordinates +X is pixels from the left edge, +Y is pixels down from the top. This particular example based on a 320x240 display but should be easily portable to other display sizes – but you have to keep in mind how the coordinate system works.

SCREEN LAYOUT

Here are a few notes about how the demonstration display is laid out. This should help you understand the design concept and allow you to begin to modify it.

The VFO display is setup for a dual VFO rig. The currently Active VFO is always on the top and the alternate VFO is just below it. Your code will need to keep track of whether VFO A or VFO B is currently selected and call the display routines to update the display. I’ll describe how the VFO displays are are defined and that will give you an idea how you might modify or enhance the display.

Active VFO - top center of the screen

#define DSP_VFO_ACT_X 60   // Active VFO begins 60 pixels from the left hand edge (I picked 60 by experimenting)
#define DSP_VFO_ACT_Y 30   // Active VFO box starts 30 pixels down from the top of the screen
                          // (Try changing it to 50 and see what happens)
#define DSP_VFO_ACT_COLOR ILI9341_GREEN   // This sets the text color for the Frequency display. Use whatever colors you like
#define DSP_VFO_ACT_BK ILI9341_BLACK      // This sets the background color for the Active VFO
#define DSP_VFO_ACT_SZ 3                  // This is text size from Arduino TFT, values 1-5 1 is small 5 is large (2 was too                                                 // small, 4 was too large, 3 was just right)

Alternate VFO – the second VFO is placed directly below the Active VFO on the screen.

There are a couple of things of interest here. For the X coordinate, instead of putting in a hard coded number I refer back to the #define that I used for the Active VFO (DSP_VFO_ACT). That way, if I want to move VFO section to a different part of the screen I only need to change one number DSP_VFO_ACT_X, and the alternate VFO will move as well. Figuring out the Y coordinate for the alternate VFO is a little more challenging. Some math is involved. Starting with the Y coordinate of the Active VFO I need to calculate where how far down the display I need to go to place the second VFO. To do that I need calculate how many pixels tall the text characters in the Active VFO are and use that as an offset. It turns out we have everything we need already defined. CH_W and CH_H are #defines that specify the height and width of a text character in pixels for TFT font size 1. Size 2 through 5 are even multiples of that – so font height for size 2 is

2*CH_H pixels and font width 

And for size 4 is

4*CH_W

pixels and so on. so we have everything we need to calculate how many pixels the Active VFO takes on the screen – we multiply the font size by the character height and add 16 pixels offset. The 16 was determined by experimentation for something that looked good. The code looks like this:

#define DSP_VFO_ALT_X DSP_VFO_ACT_X
#define DSP_VFO_ALT_Y DSP_VFO_ACT_Y + (DSP_VFO_ACT_SZ * CH_H) + 16 

Take a look the other sections of the display code and you will see similar references and calculations. The VFO A//B indicator and LSB/USB mode indicator, for example are similarly “pinned” to the Active VFO display, so if you move the Active VFO display to another screen location they will move also.

In summary - each object is on the display is defined by a set of constants that indicate the X,Y coordinates of the object on the screen and various other attributes like text size and color. The basic user interface display object is a bounded/filed text box. You can control the text size and color, and the box fill color. With this basic set of features you can implement a wide variety of user interface elements. The S-meter, for example, is a row of filled boxes.

HARDWARE NOTES

My test sketch uses an Arduino Nano. The display is an HiLetgo 2.2 Inch ILI9341 SPI TFT LCD Display 240x320, but any ILI9341 display should work. There are many sources. Please note that the Arduino has 5V logic levels, but the display requires 3.3V - so you need some sort of level shifter. I used the"HiLetgo 10pcs 4 Channels IIC I2C Logic Level Converter Bi-Directional 3.3V-5V Shifter Module for Arduino" I used hardware SPI and the pinouts are standard as follows:

        Arduino 
         Pin       TFT Pin
      -----------|---------    
          8      |  RST  - any free Arduino Pin (not used in this sketch)
          9      |  DC   - any free Arduino Pin
          10     |  CS   - any free Arduino Pin 
          11     |  MOSI - fixed
          12     |  MISO - fixed
          13     |  CLK  - fixed

That is all the wiring you need for the demonstration sketch.

You can download the sketch on the KK4DAS Github

BUILDING THE DEMONSTRATION SKETCH

Create a folder called SSB_TFT_Display_Demo

Copy all three files to that folder

• SSB_TFT_Display_Demo.ino
• SSB_TFT_Display.h
• SSB_TFT_Display.cpp

Use the Arduino IDE library manager to install the following libraries

• Adafruit_GFX
• Adafruit_ILI9341

Compile and upload the sketch.

If you build it or modify it,  it take a picture or make short video - or just let me know about it in the comments.

73 from Great Falls,

Dean

KK4DAS