Getting more ports to use on mods
You will quickly find when it comes to modifying your µBITx that one of the key limitations of the Raduino is that there is only one spare I/O port on the processor – Port A7. Ports A6 and A7 on an Arduino Nano are also limited to being analogue ports. Unlike most analogue ports on arduino processors, the nano A6 and A7 ports cannot be configured as digital ports.
However, there are solutions to this port shortage. The simplest way to rescue six digital I/O ports is to convert your 1602 display unit from being parallel fed to an I2C device using an I2C display backpack unit, which are very affordable. Alternatively, you can change out your Raduino for one of the several options available to purchase from other constructors (most as board only, but there are some completely built up units being sold). Finally you can always add a port expander, or upgrade your processor, but these will be discussed in separate articles on this site.
Turn your parallel display unit into an I2C display unit
The easiest first step to reclaiming arduino Andy KB1OIQ has posted a file on the [BITX20] IO Group files page: kb1oiq_i2c_mod.pdf that describes the hardware and software modifications that he performed on his uBITX to free up digital pins on his arduino. You will need to be logged in to the Group page to access the file.
Andy converts the LCD to use the I2C bus, thus freeing 6 Arduino digital pins for other uses. Only very minor modifications are required to the Raduino sketch (and you will need to install a different library). He documents every step involved with photos. Well done!
Removal of the two pull-up resistors on the backpack board that attaches to the 1602 display and direct connection of the I2C A4 and A5 arduino pins should suffice, instead of using a level converter board. However, the cost of adding in the level converter is negligible and works well!
Alternative backpack units
The backpack unit used byAndy KB1OIQ is an Adafruit unit that is more expensive than most. Cheaper units, for less than US$2, are available from other sources including Aliexpress.com.
Don’t forget to remove the two pull up resistors for I2C lines on whatever board you settle on purchasing. Most of these boards will, however, be able to use the Adafruit I2C display software library.
Often an upgrade to drive your display using I2C is accompanied by other upgrades, including a processor upgrade or use of an alternative to the Raduino.
There are several alternative Raduino boards available to replace the stock board. See the separate mods page for details on Raduino replacements.