An amazingly smart idea for extra I/O ports

Tom WB6B want to expand the number of digital and analog I/O pins available to him in adding enhancements to his uBITx.

He came up with an ingenious idea, by creating a Smart LCD Backpack to replace the commonly found ones on inexpensive 2×16 and 4×20 I2C displays found on eBay and Amazon.

He has uploaded a library to GitHub that allows you to program a Arduino Nano to emulate the common I2C to parallel backpack used on an I2C display (either size). The Smart I2C Backpack, additionally, allows you to read and write the analog and digital pins on the Smart I2C Display Backpack.

The package includes a interface library that you include in your code to interface with the Extended I/O functionally. Also included are two example sketches. One is the code you program into the smart backpack. The other is a demo/test program you program into another arduino and connected via the I2C bus to the Smart Backpack Display.

The Smart Display Backpack should work with firmware using standard I2C LiquidCrystal drivers such as the KD8CEC firmware.

The code uses libraries that are installable from the Arduino library manager,.  The GitHub URLs are just for reference.

The following libraries should be part of the base Arduino software install:

  • Wire
  • LiquidCrystal

Tom hopes that others will enjoy this new display and I/O expander.

And the link to the code …


Adding the v4 pop fix directly to a v3 board

Nigel G4ZAL has added the v4 pop-fix to his v3 board by placing components directly onto the v3 board.


  1. Swap out R70 from 100 ohms to 1K.

  1. Drill a small hole (0.7mm or similar) to the right of R70 so as to be able to fix the 2N7000 transistor.
  2. Pin 2 of the 2N7000 is soldered on the underside of the board (ground).
  3. Scrape a little varnish from the tracks and tin ready to fix the 2N7000.
  4. Add some Kapton tape to stop any shorting of components.
  5. Add the remainder of the components and run a bit of enamelled wire to the trace near the Raduino headers to pickup the T/R line.

Seen from the front of the main board (ignore the cutouts on the front of the board)


LED power out indicator

Lee  “I Void Warranties” N9LO ran across this circuit when looking for a transmit indicator for his Small Wonder Lab PSK31.

[Note the circuit was originally drawn incorrectly, but has now been updated]

Lee threw it together (there are not many parts) and it lights up bright and solid for CW and you an watch your modulation on SSB.   I can really see the difference when I switch in my SSM2167 module.

Jerry KE7ER recommends placing the circuit before the transmit LPF, not at the antenna port.   The diodes potentially create a bit of harmonic content that the LPF’s would remove.


KD8CEC firmware hint – CW frequency display

The KD8CEC firmware provides a lot of customisation features through uBITx Manager software.  Many user of Ian’s firmware are not aware of all the built-in features of his firmware.   This is one such instance!

JJ1EPE raised a concern that his display in CW mode was “off frequency”.  Well, it was from his perspective, but then the display was all the time showing the TX frequency not the offset frequency where the station he was listening to.

CW offsets create headaches in how you represent the frequency on a display.  In SSB the frequency you see on the display is the frequency of the suppressed carrier on receive and the same on transmit.   If you tune to the carrier frequency of a received station you won’t hear anything.  To get a sidetone we have to tune off the transmit frequency by a few hundred hertz.  Most people have worked out how to set the offset on the uBITx.

The standard that Ian KD8CEC has applied is to always show the TX frequency  by default (except where RIT or SPLIT mode is selected).

However, if you want to change the approach, do the following in uBITX Manager:

– Enable Adjust CW Frequency

– Shift Display Frequency on CWL, CWU Mode

If you select this function, the LCD will show the frequency at which the radio is being transmitted (the offset you prefer is added or subtracted to the actual RX frequency reflecting the CW-L or CW-U mode selected).   This may be just the thing you were looking for!


Getting prepared for the JackAl

Some of you are waiting with baited breath for the JackAl Board, announced by Jack W8TEE.   You can get yourself geared up for the JackAl by pre-purchasing some of the kit required, as it is due to be released shortly.  You will need a colour touch display panel, a Teensy 3.6 processor and associated Teensy audio board.

Display panel

There are two display options for the JackAl board: 5″ or 7″.  Neither is likely to fit in your existing µBITx enclosure, so you may also want to purchase a new enclosure.

The panels can be purchased from Their order numbers are:

ER-TFTM050-3 (5″)
ER-TFTM070-5 (7″)

Both displays use the following options:

4-wire SPI interface
Resistive touch
No font (the library is being used for fonts)

Both are 800×480 displays using the RA8875 chip. If you run the samples using a touch screen, make sure you run the Calibration sample program first.

Teensy 3.6 and audio board

The Teensy 3.6 and its associated audio board can be purchased from the manufacturer’s website or from other sources.


MicroSD reader extender

Rohn KR0HN  was “parts shopping” online when he came across a microSD card extension cable.

This could be used to extend the microSD card slot of the Nextion display out to the exterior of the case.  This would be handy for upgrades to the display firmware as new features become available for your display.

The link to the amazon page is:


Dimming your Nextion display

Ian KD8CEC has been looking at power consumption on the Nextion display and how to effectively dim the screen for portable µBITx work, where you want low current drain.

The following picture show’s Ian’s display (2.8″ TJC Chinese version) at Full Power:

And the screen fed with a series 50 ohm resistor (1/2 watt rated or more):

The slightly dimmer display halves the current consumption from 89mA to 44mA with a series 50 ohm resistor (made up of two 100 ohm resistors in parallel (or 3 x 150 ohm resistors in parallel).  The Nextion screen has a built in software dimming function, and this can be adjusted in Ian’s Nextion display firmware.   However, the feature generates noise in the µBITx and is not recommended.

Resistor installation

Installing a series resistor (with a value between 20 ohms and 100 ohms) in the +5V power lead will cause the display to be dimmed, but function normally (except for use of the micro-SD card reader).  The resistor could be installed across a slide switch or toggle switch (with one pole shorted and the other going through the resistor) to allow for two settings (normal, dimmed).   This could be handy for night time or portable use.  The circuit diagram for this is as below:

For further details see Ian’s website.

Breadboard uBITx

Jon Titus  KZ1G  shows off his breadboard construction  technique, which he uses while his rig is under development.  The board is mounted on a piece of plywood and usea 1/8-inch clear plastic as front and rear panels for controls and connectors. This “breadboard” technique has been used by Jon for other projects, because it lets him rearrange control locations, ensure clearances between components, jacks, heatsinks, etc.  In this way he doesn’t ruin a nice front panel when later adding an extra pushbutton or switch, etc.

After learning about the W0EB and N5IB RadI2Cino (Rad I2C ino) project he needed more room for the replacement board and a larger LCD. A section of plywood was glued on the front (see photo) and the front panel  was then able to be moved forward by about 4 cm.   Jon quickly added an extra pushbutton, and drilled holes to mount the LCD.

However, when do you make the call to put the whole thing in a proper metal case Jon?