So, you have this project, it uses an Arduino or Raspberry Pi or maybe even a plain old LC VFO and now you need to have some sort of readout.
3 Inch Color TFT
You are now faced with a menu from a Chinese Restaurant. One choice from Column A and perhaps two from Column B, capped off with a single choice from Column C. Yes, that is the dilemma.
The LC VFO in the old days could be mated with a combo Vernier Drive and semi-circular dial scale where you hand printed the frequency info on the scales. National and James Millen made such units.
Today's version is a 3X5 File Card marked with a fat black sharpie pen. Crude is a great word! Or if uptown you could use one of those packaged LED counters that can be offset by the IF. (San Jian about $15 for a six-digit unit.) Besides whom in the proper frame of mind would use an LC VFO when the Digital VFO is so much better.
Moving to the Digital Side we have the Chinese Menu. At the shared top tier, we have the 16X2 all the way to the 20X4 LCD's. Needing only 4 connections if you use the Backpack adapter, a lot of information can be displayed and in fact using some menu tricks the 16X2 can be turned into various screens and thus not just a single 16X2. In passing I have also used an 8X2 which is really a challenge which is shown here with an early Bitx40 that did not come with the Raduino.
If you use the Xiao RP2040 MCU, you are somewhat limited to a lesser number if IO pins, and thus the 4 wire LCD is likely the 1st first (and maybe only) choice.
The LCD's come in backlit and non-backlit (bad choice) as well as various coloration such black lettering on a seasick green background or my favorite, Juliano Blue background with white lettering. [The non-backlit are really cheap but hard to read in direct sunlight.]
A word about ease of implementation and cost. The 16X2 is like the old camera ad (point and shoot) -- point to one of 16 locations and tell the code "Print here". A bit tricky is that the spaces are numbered 0 - 7 and 8-15 and Line 0 and Line 1. The LCD's can be found much cheaper than the Color TFT's. The backlit versions can be really power hungry so having the display lit all the time in a portable setting can drain your battery in short order.
Of note the LCDs operate on the I2C buss and therefore share the same 4 pins as the Si5351. Information in the code must designate the I2C buss location of the LCD such as 0x27 (pretty much the standard). And of course, Adafruit in some of their offerings use a custom code. If your LCD doesn't display and is wired correctly, there is a good chance it is your I2C address in the code.
The other side of the Digital Menu are the OLED's and the Color TFT. This is where the menu becomes a fold out road map. The OLED's have limited color choices but can be really small. The equivalent to the 16X2 is 1/2 inch high by less than 1-inch-long OLED. This takes up very little panel space and the current drain is better.
Now on the menu is the Color TFT (Thin Film Transistor) LCD technology. Short answer better image quality and faster addressability. Another huge plus --screen sizes up to 5 inches that don't require a home loan. I have Color TFT displays less than 1 inch square to 3.5 inches. For us older folks -- the 3.5-inch job sure makes things easy to read.
But the Color TFT's need about 7 to 8 wired connections and more panel space because of their size. The big bonus is colors and viewing area -- the big negative -- you have to have some programming skills and patience.
One huge problem is what I call overwriting. Let's use an example. I often display the mode such as USB or LSB. A couple of ways to do this is to have one location where you simply change the letter U to an L and the SB is always fixed. So, you hit the switch for LSB and the U changes to an L. Going the other way on USB the L changes back to U. Unless you make some provisions in the code you will see U and L simultaneously.
So, in the code if you are switching from USB to LSB, the code will first say the print color in the "U" space with the background color (usually black) and then the code says print the letter L in the normal print color. Thus, the overwrite is in black and the next overwrite is the proper color. In transitioning back, same set of code for the L and U.
I frequently just use two separate blocks of space where I write USB or LSB but use the same overwrite by calling out the print color as black or the proper color.
The programming is a time-consuming effort for the Color TFT and likely for many the 16X2 is the answer.
The sensibility of displays all comes down to the effort needed or required. For just basic info it is hard to beat the 16X2 which also likely costs the least and involves rudimentary programming. While I did not previously mention it, many of the Color TFTs are touch screens and this give the user a more hands on control of functions. This is kind of a curse for those of us with FFS.
73's
Pete N6QW