WA6ISP uBITx replacement Raduino

Mike Hagen, WA6ISP has previously supplied Raduino X and Raduino XP alternatives to the builder community for the BITx40 units.    He has been asked by many builders whether a µBitx Raduino replacement was planned.

He now has designed, built and tested a µBITx Raduino replacement.  This comes with the extra feature of having an i2c 16 port I/O expander on board. The Microchip Expander IC uses the Adafruit Library MCP23017 to create 16 more Digital Pins.

This replacement board is slightly bigger than the standard Raduino and has the Ardunio Nano facing towards the left rather than to the right.

Email Mike for further information or to order.   The cost of the bare board is US$12 and the built up board is $46.  Note that the bare board will require you to source all parts and  mount some fairly small surface mount devices.

µBITx constructors now have several alternatives to choose from in considering a replacement Raduino board: the WA6ISP uBITx Raduino, the W0EX Radi2cino and VK4PLN Raduino replacement.

Using the Adafruit si5351 Board

Many constructors are using the Adafruit si5351a i2c board with their µBITx as part of a Raduino replacement (often in conjunction with a processor upgrade and feeding the display with an i2c daughter board).

Note that the Adafruit board does not have 0.1uF capacitors on the outputs of the three clocks.   You will need to find a way to incorporate these capacitors in your circuit.

Reclaiming Pins on the Raduino

Don Cantrell ND6T has reclaimed two relatively unused pins on the Raduino for reuse.  Check out the details here or on his website.

When the μBITX was manufactured as a “semi-kit” the Raduino control module was designed to simply plug into the main transceiver circuit board. This made wiring easier and also permitted close and controlled connection for the high-frequency synthesizer outputs. Much more reliable than extra cabling and shorter runs, too. The downside is that more of the input/output pins from the Nano micro controller are dedicated to native functions of the radio, and only two are available for additional modifications by the user.

One of those pins is already used as the key input for the CW mode. That left just one pin, an analog capable one, to be used for such purposes as monitoring supply voltage, an S meter, an RF power meter, or VSWR indicator.

The two available “spare” pins are the only two that do not have an internal “pull-up voltage” option available on the Nano processor. These pins are designated A6, and A7. In the initial design the A6 pin is used as a CW key input and so requires an external resistor to the +5 volt supply in order to detect key closures. That detection requires an Analog to Digital Conversion (A/D conversion) and consequent decoding and processing of the resultant measurement in order to determine each key closure.

It worked, but was highly prone to error, especially if key, cable, and connectors had anything but excellent low resistant contacts and connections. I found myself regularly burnishing key contacts and having to solder across every press-fit junction in both key plug and jack. Add to that the added shielding and bypassing of the key line and there still remained an annoying glitch or two at high speed. Ah! Opportunity!

Digital pins D0 and D1 are used for serial communication. D0 is labeled “RX0” on the board, D1 is labeled “TX1”. If you were to use an RS-232 arrangement, these would be the pins that you would have to use. When you use the serial monitor (like my pocket generator uses) then these are the two pins used. Even when you program the Nano, the on-board USB controller circuit uses those pins. However…

When you are not using a serial communication function, these two pins are “up for grabs”!

Don ND6T opted to use D1 for a key input. As long as I don’t have a key plugged in and  pressed, the program loads nicely into the Nano and no one is the wiser. Since this pin has pull-up voltage capability, I don’t need an external resistor. Without A/D conversion the key is sampled in microsecond intervals. Since it uses TTL logic levels (0 and +5 volts) it is not prone to poor resistance connections, bypass, or shielding problems. Works like a charm.

Additionally, these two pins have their own little LED indicator lights on board the Nano. When one of the pins is taken to a low state (close to ground potential) the corresponding LED lights. Those nifty little indicators are usually hidden since the Nano is placed between its circuit board mounting and the display, but if you position yourself just right then you can see it light up. Nice little trouble-shooting extra!

Use the attached photo to locate the two pins on the back side of the board. The end pin is D1 and the next one is D2. Yes, they are out of order with the remainder of the pin numbers in that row. Cut a two pin section of right angle .1” spaced header block. Use alpha cyanoacrylate (Krazy Glue®) to mount the body of the plastic block to the printed circuit board, with the pins snugged up next to those two on the circuit board (D0 and D1). Then solder the new connector to those pins. That makes it convenient and easy to connect to your key jack or whatever else you want to sense or control.

The remaining digital pin is a good one to use for an added Function switch. Don uses it as a convenient access to a menu for changing sideband modes, switching VFOs, activating RIT, or adjusting my IF band pass.

That leaves two analog inputs. Hmmm!


RadI2cino … another Raduino replacement

Jim Sheldon W0EX  has announced the availability of the joint effort from himself and N5IB – the RadI2Cino (prounounced “Rad ee too CEE no”).  This is an almost “Drop In” replacement for the original uBITX Raduino card.

The attached PDF (N5IB_W0EB_RadI2Cino) contains the complete information on this new Raduino replacement.

In summary, the changes/enhancements that have been incorporated in the RadI2Cino include:

  • I2C is used so the 16 pin LCD display header has been eliminated
  • The LCD display contrast pot has been eliminated
  • The 16 pin and 8 pin uBITX headers are retained and connect in the original fashion
  • Arduino NANO I/O pin assignments have been rearranged to free up digital and analog I/O pins
    a) D8, D11, D12 now used for key, paddles, and PTT.
    b) D10 used for an A/B split selection button.
    c) D9, D13, A3, A6, A7 now available for other needs.
  • The LCD display is operated via an I2C bus connection.
    a) Contrast control is now part of I2C interface “backpack”.
    b) Larger, 4-line displays are supported.
  • The TO-220 5 volt regulator has been replaced by a surface mount 7805 1 amp regulator.
  • A surface mount 3.3 volt regulator has been added.
  • A 4-pin header has been added to give access to the I2C bus.
  • A logic level translator has been added to the I2C bus to protect the Si5351 clock chip.
  • Manufacturer-recommended RC de-bouncing for the rotary encoder phases has been added.
  • Provision is made for an optional dropping resistor to reduce regulator dissipation.
  • Several powering options are provided, selected by shorting jumpers.
    a) power everything through the NANO via the uBITX +12V rail**
    b) power the NANO from the uBITX +12V rail, and the rest via the 5V regulator**
    c) power everything from the board mounted 5 volt regulator.
    d) power the Si5351a from the NANO’s 3.3 V output.
    e) power the Si5351a from the on-board 3.3 V regulator.
  • Though the PC board is slightly longer, mounting holes compatible with the LCD display are retained.
  • An additional 8 pin header is added for access to the newly free I/O pins.
  • Uncommitted PCB pads are provided to connect serial I/O and NANO Reset. NANO mounting pads are intentionally oversized to allow for a low profile, machined pin, socket for the Nano.
  • Heavy use is made of silk-screened labels to identify signals and functions.

** If the optional dropping resistor is not used DO NOT EXCEED 12V when using these power options.


More boards are on order but due to the Chinese New Year they won’t be shipping until around the end of the month.

Jim asks that  all inquiries and orders be held off until after he announces the availability of the next batch.


Another Raduino replacement coming


Nik VK4PLN has been working on a simple “open source” Raduino replacement board.   He has now provided photos of both sides of the board.

It will use the Adafruit Clock board. All devices will, therefore, run at 5v.  inouts and dimensions are similar to the original so it can be used as a direct drop-in replacement, or it can be modified for i2c display and other GPIO mods.

Nik is hoping it will work out cheap (50c a board, $3 nano, $8 Si5153 board plus a 7805 regulator and a few other bits and pieces).  He plans for the board to accept either Surface Mount Devices or Through Hole devices, particuarly for the capacitors and resistors…

It is hoped that this would be a cheap easy build for a Raduino replacement. An initial assessment of costs (ex Ebay.com) is as follows:

VK4PLN RadinoI2C board : $8
LCD + Backpack : $3
Si5351 : $8
Arduino: $4
+bits : $2
= $25, not too bad.

Nik invites constructive comments and thoughts


Raduino Repair Service

Jim Sheldon W0EB is offering a new service to uBITX owners in the US (sorry no service is provided to foreign owners) to repair Raduinos.

Jim has just finished designing and building a Raduino test fixture that allows him to look at all the signals coming out of the board and also hook up all the digital controls to the board. He has the equipment in his shack to replace the Si5351 clock chip if it is bad and he can also replace a bad Nano (but the customer must provide the Nano).

He’s not sure how long he will be able to offer this, but he is aware that there are a few BITx owners out there that have somehow blown up their Raduino.  It is not that easy to get a replacement at the moment.

DO NOT send Jim your Raduino in need of repair without first contacting him and discussing the problem.  He may refuse to work on it if it appears too badly damaged – that’s at Jim’s discretion.

The offered service is ONLY Raduino repair, not complete uBITX repair.

Contact Jim via his QRZ.com  address (his email address is listed as well).

Convert your uBITx display to an I2C Display

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!

[EDITOR Comment – removal of the two pull-up resistors on the additional board and direct connection to the I2C A4 and A5 ardunio pins should suffice without use of a level converter board.  However, the cost of adding in the level converter is negligible and will work well!]


Damaging your Raduino

A post fromJustin KN4FAW reminds us all that it is VERY VERY EASY to damage your Raduino.

Justin says “So, I assembled my Bitx40 kit, at this point it was just wires laying on my bench. I wired up the function button, tested, everything working great. Accidentally touched the ground from function button (orange wire) to 12v while moving stuff around. Now my LCD only shows squares, and I can not tune the radio.  Am I screwed?”

Answer: Yes.

Watch out for the two orange wires on the two different connectors.    Check and double check your wiring before powering on.

Justin isn’t the only one who has done this.  Several other group members fessed up to doing the same, or similar.   Arduino Nano pins are not tolerant of 12v.  There are many other ways to destroy an Arduino Nano pin.  You can read about 10 ways to destroy an arduino here.   There may be quite a few more ways as well …

Mike Hagen WA6ISP comments:

“I recommend in building these radios that you change all ground wires to Black and all Power (5 or 12V) to Red. Reserve these colors for just 2 purposes. You can use the wires you remove for additions.

“Leave the molex pin on them. I have a lot of spare Brown ones. I can’t stand an Orange wire being B+ (the term for us old Valve guys)! 26AWG stranded works great.  I purchased a bunch of colors at All Electronics. Molex pins can be acquired at Tayda and Mouser.

“You don’t have to be in such a hurry and blow things up. Check your wiring several times. You could even make a connector chart with J numbers and pin numbers with the associated wire color.  Match it up to what is on HF Signals. It may mean you catch a mistake and save a lot of trouble shooting?”