uBITx in an aluminium briefcase

Aarne Haas WY7ATH has just finished a µBitX build in an old ‘toy’ briefcase.  It makes for a good enclosure – along the lines of µBITx builds in P cases. There is a small manually switched fan inside blowing on the final heatsinks when operating digital modes.  Nice one!

Nextion Displays – Hints for loading display firmware


Michael VE3WMB brings us some hints when installing Nextion displays:

1) The Display wants the microSD card to be formatted as FAT32.   Make sure your microSD card is no larger than 32GB

The default in  Windows is to format cards > 32 GB as exFAT, which the Nextion will not accept. In fact Windows 10 probably won’t even let your reformat a card this big as FAT32.  (I am sure if you dig deep enough there might be a way to do this. I am not a Windows GURU).

Currently you only need a 2 GB card,  so if you need to buy one for this purpose try an 8GB card.  It is also worthwhile buyong a brand name card (like Sandisk).
Some no-name cards are slower than cold molasses to read from and write to.

2) If you have a problematic microSD card, when you power up the rig you might not see anything on the display, not even a backlight !  

I spent considerable time trying to solve what I thought was a wiring/power problem to the display when it was a bad SD card. When the I removed the card and power-cycled the rig the Nextion display came up fine with a demo program that was already loaded.  So my recommendation is for the initial power up of the display don’t insert the SD card. That way you can be sure that you have it wired up ok before you start messing with SD cards.

3) Beware, ground and +5V connections on the Raduino going to the Nextion Display are adjacent to each other. 
I recommend that you check and recheck your wiring several times before applying power.  It is very easy to accidentally swap these and you won’t be happy if you do.  As they say, “An ounce of prevention is worth a pound of cure”. One group member has already found this out the hard way.

Mark AA7TA adds:

4) Duplicate .tft files (including hidden files) will cause grief on the Nextion

You may get a message on the display that the load failed because there is more than one .tft file on the SD card.  This can happen even when you look and you see only one file.

You need to be sure to enable viewing of hidden files in file explorer (Windows) or finder (on a Mac)… There’s probably one hiding there with the .tft suffix that you need to delete.  I don’t think either operating system will show hidden files by default. The same goes for Linux.

Mark notes that a 1G SD card is plenty big enough for the current tft file.

Keven adds, “Linux doesn’t show hidden files by default.  But you can see them by typing:

ls -al

in a terminal window when you’re in the directory you want to examine.  To hide a file, rename it with a dot (‘.’) as the first character.”

Mike ZL1AXG adds:

5) Make sure you install the screen the right way around

Power up the display before you start making holes and check the orientation of the display and that the screen is functioning correctly.   As with the 16×2 display, it is possible to install the display upside down by mistake!  Given it is not symmetric (there is a wider bar to the right hand side of the display) care is needed!  The inner silver line on the screen defines the touch sensitive boundary.  Cut your hole so that the screen fits so the line is just visible around the outside edge.

Dimensions of Nextion displays can be found for this zone on the itead website. Click on your display and near the bottom of the page you will find a link to the screen dimensions.

6) For most people the 3.2″ screen or larger will be best

A 3.2″ screen is only just big enough to feel comfortable for us fat-fingered chaps.   It is also just wider enough to reuse the width of the 16×2 screen.  Smaller screens inserted in the space where the 16×2 screen currently lives will require an additional aluminium or plastic plate to be added to the front panel to cover the existing width of the 16×2 screen.


Definitive audio pop fix

With the release of the v4 board from HF Signals, we finally have  a design for an audio pop fix that can be applied to the v3 µBITx board with few additional parts.

Mike ZL1AXG has completed this mod and can vouch for it have removed all unwanted pops (on both transitions from RX to TX and TX to RX). It doesn’t kill the CW sidetone.  His application of the mod is described below.

The mod can be placed in the same position on the v3 board as in the v4 design,  using a simple Dupont header as shown below, but there are other ways of achieving the same result.

This mod only involves 5 parts.   It is now the uBITx.net recommended mod to fix the audio pop.  The audio pop fix summary will be updated shortly.  All other fixes are now effectively redundant because they are more complex.

NB – This is an extract from the circuit diagram on hfsignals.com.  There is an error with the numbering of the leads on Q74.   Check first, before wiring up!

Parts required are:

  1. 2n7000 MOSFET or similar (Q74)
  2.  1 µF ceramic capacitor (C79)
  3. 1N4148 or similar silicon signal diode (D14)
  4. 100K resistor (R78)
  5. 1K resistor (R70)

Complete the following steps:

  1.  Locate R70 (100 ohm) resistor on the right hand side of the board when looking from the front panel and remove this resistor.
  2. Drill a small hole through the board roughly in line with the two solder pads for R70 in front of the relay 7/10 of an inch to the right.
  3. Install a standard dupont female header with 7 sockets (spacing 0.1″ per pin) on to the board (see first photo above).    The first two pins are bent over at 90 degrees and solder to the pads for R70.   Pins 3-6 are removed.  Cut them off underneath and then pull them out with a pair of pliers.    Solder the final pin 7 underneath the board
  4. Install parts on the  plug in board as per the circuit diagram below, and use a male dupont pin  to connect to the T-R line.  Plug the board in to its socket, connect the T-R line, and you should have a nice quiet transition going to TX.
Step 1 & 3: Install the dupont header to replace R70. Pins 1 & 2 on the left are bent over at 90 degrees and soldered to the pads. Pins 3-6 are removed. Pin 7 passes through a new hole drilled in the board
Step 2 – Reverse side showing pin 7 soldered to the underside of the board to securely attach the female dupont header above
Step 4: Install the components on a small piece of perf board. The purple wire connects to the T/R line on the raduino.

New graphic for uBITx.net

Some of you will have been sufficiently observant to notice that the graphic at the top of the www.ubitx.net webpage has been updated.  This is because Mike ZL1AXG has installed a Nextion 3.5″ touch screen on his own µBITx.    Careful work with a drill and file will yield satisfying results.

He also installed the latest pop fix from the v4 board (see the separate article).

Nextion Displays – Current draw

Lowell has tested current draw on a 2.4″ and a 3.2″ Nextion display following questions from constructors over the likelihood of cooking the existing 5V regulator.  With a supply voltage of 5.04 VDC, the 2.4″ display drew 125 ma. and the 3.2″ display drew 110 ma. Both  displays were at full brightness.   While the figures are slightly above those listed on manufacturer’s website, this suggests the 5V regulator should be fine.   If in doubt, add a heatsink!


Warning for those using a Teensy 3.5 or 3.6 or Biteensio board

Jim Sheldon, W0EB notes that the tiny power jumper on the back of the Teensy 3.5 or 3.6 MUST be cut when using external power to the Teensy (from the BITeensio board). Left intact, it is possible to have power being applied to the Teensy through BOTH the BITeensio board AND the USB connection, especially during programming or remote control operation via the USB port. This may cause board power and USB power to conflict with each other and can destroy the Teensy.

The jumper is pointed out on the back side of the pin-out card that comes with every Teensy and it states: “Cut to separate VIN from VUSB, if using a battery charger or external power.” with an arrow pointing to the jumper between the two pads.

Carefully cut this tiny jumper with a very sharp hobby knife to avoid any possible problems.  After cutting the jumper, you will have to power the board externally through the BITeensio card (or other means) when programming or re-programming the Teensy through the USB port.  This holds true for Teensy boards used in just about any application, not just on our BITeensio board.


KD8CEC releases CEC Beta firmware to support Nextion display

Ian Lee KD8CEC has released Beta firmware for the µBITx that supports Nextion colour touch screens .  He has also released matching files for installing firmware in the Nextion displays for 2.4″ and 2.8″ screen sizes.   No programming is required to use these displays.

The photo above shows the touch panel display.  Pressing on the screen will perform functions like changing band (up/down), changing frequency, adjusting the Attentuator (ATT), IF Shift and RIT, and going into Split mode.

See Ian’s webpage for details about downloading the various firmware options along with detailed instructions.

JackAl Board

Now you can have a look at a partially populated JackAl board thanks to this photo from Jack W8TEE in response to a question about a LA4425 as a replacement to the TDA2822.

The highlighted square in green is the audio amp stage of the JackAl board: a 7W TDA7266M.  Seems like you could really blast the neighbours with that one!

In case you haven’t figured out what the JackAl board is about: it is a supplementary board that hsould be released in the next few weeks by Jack and Al, that adds a Teensy 3.6 processor, and a number of other mods, all on one board.  The Teensy will give the µBITx new features like DSP.

Scratch built uBITx

The original uBITx design was published by Ashhar Farhan in March 2017.  A number of people have built a uBITx up from scratch.

Richie KM4TLR has Eagle layout files for the RF sections of the UbitX if you are building one from scratch.  He  took a modular approach, so there are several circuit boards that you could make a UbitX or a single conversion design.   The photos tell it all.