Parallel IO project

I have 2 older ham radios that I bought computer interfaces for. The ports are similar to a parallel port, in fact I once had a Visual Basic windows app that I wrote, that communicated with them through the computers' parallel port, but it wrote to the port directly setting/reading each bit and some control lines.

In total, to control the radios the connections are:

8 data lines
1 Read Pulse
1 Write Pulse
1 SRQ line (Service Request line that shows data is being transferred to/from the radio)
1 Data Valid line that shows data has been received
1 Send line, which will put the radio into transmit mode
1 Squelch line, goes high when a signal is received
1 Ground

So there's 15 data lines I need to read/control each radio, and I have 2 radios, so I would need 30 i/o data lines.

I currently have a UNO board I bought back in 2015. It's an old board, but hopefully it'll do what I need.

What add-ons should I get to be able to control this many i/o lines?
I believe they make serial to parallel port adapters, but not sure if they would work for this, plus I would need 2 of them to accommodate the number of i/o.

Some I2C I/O extenders?


or use that chip directly youself.

and yes, they would work perfectly in this circumstance.

Just code. :wink:


Looking at my stash that I bought, I found 3 Nano DCCDuinos, which appear to have 16 digital i/o lines. Would that work? Still going over documentation on it.

Just depends on what kind of fun you want to have.

Using a board and planning on needing every I/O pin is a certain recipe for running out… be sure you can do it.

And do these need to communicate or cooperate with each other?


The boards/radios do not need to communicate with each other.

I'm trying to digest how the DCCDuino actually physically works. It looks like these can be standalone or work with my UNO?

I would like to have 1 USB cable going to the arduino, and 2 cables coming out to each of the radios... just to cut down on the usb requirements
if one USB per radio works, that might be fine as well.

Or buy a Mega...

I have some Nano DCCDuinos.. the documentation says I can select Nano w/ATMega328. Is that what you're talking about?

The chip on my Nano is a Mega328

Colloquially the Mega2560 board is called a Mega.

ATmega is the processor family

Ok, I may have my terms wrong, still new to these devices.

This is what I have:
Qty 1 - Arduino Uno Rev3 | Arduino Official Store
Qty 3 - Arduino Nano | Arduino Official Store

Who are the makers of the ham radios?

Icom 751A, 271H, 471 series.

Interface is the IC-EX309 ICOM IC-EX309 manual

Many thanks for you reply.
You may ask to your local ham section.

OK both those are complete Arduino systems, either is suitable. Some opinions vary (!) as to which is better…

I use the UNO mostly, because that’s what I have handiest.

Dupont wires of variously gendered ends make lashing up either board with many of the modules you can get easy, I bought a bunch of every kind, so same argument for the not UNO board, just different gender cabling.

Often when if I actually finish or nearly finish the software on the UNO I move that code to one of the many other boards available based on the mechanical constraints.

HTH and sry if you already knew or figured that all out.