Archive - September 2019

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

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

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.

 

ACOM Director Classic (ACOM 2000A Only) Updates – 0.7.2 & 0.8.1

Following feedback from ACOM regarding the remote power on using the RPON module for the ACOM2000A, two new versions of ACOM Director have now been released.

Version 0.7.2 is now available for anyone who was previously using 0.7.1 and does not want to use the experimental 0.8.x releases

Version 0.8.1 is now available for anyone who was previously using 0.8.0

These contain the following changes

  • Renamed to ACOM Director Classic as this is now the legacy version
  • Increased the RTS+DTR impulse time from 3 seconds to 10 seconds when attempting to remote power on the ACOM2000A

The increased impulse length from 3 to 10 seconds for remote power on is due to the power on failing on many occasions because the 1000uF electrolytic capacitor in the RPON adapter input does not get charged to the required voltage level. The most likely reason for this is the more recent USB to RS232 converters not properly meeting the RS232 standards.

These versions can be downloaded from the following locations

0.7.2 Download

0.8.1 Download

With regards to ACOM Director Plus, work had stopped for a while due to some extremely time consuming work comittments, these should be coming to an end soon however they have prevented me from furthering the progress of this. They’ve also meant i’ve not been able to monitor my radio related email very often, so if I haven’t responded to you, my apologies, I should be in a position to catch up very soon.