Category - Electronics

When is an RS-232 port not an RS-232 port (ACOM 600S RS-232 Mod)

10th September 2019
M0YOM
ACOM Director, Amateur Radio, Electronics, Projects
2 Comments

I have been attempting to get the remote power on capability of ACOM Director Plus working with the ACOM 600S however no matter what I tried I was unable to make it work. I tried swapping to a null modem cable and amazingly the remote power on worked perfectly, however I could no longer connect to the amp from the computer.

On closer inspection of the manual, it would appear that there is something unusual about the wiring for the RS-232 port

At first glance everything seems fine, however pins 2 & 3 (TxD and RxD) are wired to use a straight through RS-232 cable, but pins 6 & 8 (DSR and CTS used for remote power on) are wired to use a null modem cable. This means that for full control of the amp a custom cable must be used.

What peaked my interest is the fact that pins 4 & 7 are noted as Not Connected, these are the DTR and RTS lines and are what’s used to tell the amp to power on. In order for this to work they must be connected to pins 6 and 8. It occured to me that it should be possible to make a modification to the amp to enable it to support a regular straight through RS-232 cable.

To that end i’ve put together a mod which can be found over at ACOM 600S RS-232 RPON Mod which details how to do this. It’s only useful if you intend to use the RPON capability through the RS-232 port, however it will avoid the need for custom cables and is still backward compatible should a custom cable happen to be used in the future.

IMPORTANT – YOU SHOULD NOT ATTEMPT THIS MODIFICATION UNLESS YOU ARE CERTAIN YOU HAVE THE SKILLS AND EQUIPMENT REQUIRED, YOU COULD DAMAGE YOUR AMPLIFIER. THIS MODIFICATION IS NOT ENDORSED BY ACOM. NO RESPONSIBILITY IS TAKEN BY M0YOM, ACOM OR ANYONE ELSE FOR ANY DAMAGE OR INJURY THAT MAY RESULT FROM PERFORMING THIS MODIFICATION. PERFORMING THIS MODIFICATION WILL LIKELY VOID YOUR WARRANTY.

 

When a Null Modem Cable is not a Null Modem Cable

5th September 2019
M0YOM
ACOM Director, Electronics, Off Topic, Programming, Projects
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While working on the next update to ACOM Director Plus (yes, work is now continuing on it), I couldn’t figure out why my code to turn on the ACOM600S was not working. I’d previously put this down to the fact that I have an early model and perhaps this wasn’t implemented then. I resorted to using my scope to check that the DTR and RTS lines were in fact being activated properly which is when I discovered that my Null Modem cable i’d been using for years now is not in fact a proper Null Modem Cable.

A normal (proper) Null Modem cable has the following wiring, notice the crossover of the DTR & DSR pins and the RTS & CTS pins, these are used for the remote power on of the ACOM600S, ACOM1200S and ACOM2000A with the RPON Module.

However after checking the wiring on my (commercially purchased) Null Modem Cable, I found it is actually wired like this.

As pins 2 & 3 are crossed, it still works fine for normal serial communications (without handshaking obviously) however all other pins are straight through, so anything relying on the proper use of handshake signals will fail.

The moral of the story, if you have issues with remote power on of the ACOM600S, ACOM1200S or ACOM2000A (or anything else that makes use of any control pins), make sure your Null Modem cable is actually wired fully to the Null Modem standard and not a half baked cable like mine.

 

FTDI – Serial Killer, Not quite

25th October 2014
M0YOM
Amateur Radio, Electronics, Guides
8 Comments

Many of my fellow radio amateurs will be familiar with USB to Serial adaptors, the lack of RS-232 ports on modern computers mean they see plenty of use within the radio amateur community especially for CAT control of our Radio’s.

One of the most popular (and the one offering the best compatibility) is the FT232R chip from the scottish company FTDI. They have built a reputation for producing great USB UART IC’s with excellent compatibility and more importantly drivers that are included within windows. These devices are found in thousands of other devices from aurduino’s to 3D printers. Their popularity however means that there are a whole host of clones and couterfeit devices out there, most of which are indistiguishable from the real thing and it seems that FTDI have decided to do something about it by rendering these fakes inoperable.

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