Necessities for communication over RS-232.


Here you will find what's needed to connect your tape recorder to your computer using RS-232.


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windows
I have windows too.

 

 

 
Hi-tech loopback device
Loopback test: Pins 2 and 8 at the tape deck end are connected.

The tape recorder.

Most tape recorder types A8nn and C27n come with a 9 pin D-sub (DB-9) connector. The Studers need to be equipped with a serial remote controller 1.810.751. The Perl script works with this controller only. This controller and its DB-9 connector may not be installed. To make the matter more complex, another controller may be installed as well. That is the serial remote controller 1.820.751. The latter implements the SMPTE/EBU standard over RS232/RS422, the Perl script does not work with this controller.

In order to use RS-232, there are a number of jumpers and DIL switches to watch. See the service manual for your Studer or Revox . First check whether your tape deck has the 9-pin Sub-D socket. If it is there, your tape recorder needs to be set up for RS-232 use, or else the tape recorder will not respond. Then there are settings for baud rate, data bits, stop bits and parity. See the manual for that. For the moment you might leave the tape deck setttings as they are, in most cases they are already set for use with RS-232. The script allows you to configure the settings to match the settings of the tape deck. The script settings default to 9600,8,1,none.

The computer.

Every decent computer or tablet is suitable. As operating system recent versions of Windows, Linux, FreeBSD and OS X will do. Your computer should be equipped with an RS-232 port. If it isn't there, you can use a USB-to-RS232 adapter. I used a cheap one from Conrad, a LogiLink AU0002B. This adapter is based on a Prolific PL2303 chip, it cost about 10 euros and works well.

The software.

Linux, FreeBSD and OSX.

You need the Perl interpreter and two Perl modules (one for Windows). On most versions of Linux, FreeBSD and OSX the Perl interpreter is already installed. Check that, using a terminal, with perl -v. All Perl-versions from 5.10 and later can be used. Additionally, you need the Perl modules Term::ReadKey and Device::SerialPort.
For Linux: These modules may be found as packages in your distribution set. Then you can install them the usual way with rpm, yum or any other package manager.
FreeBSD: Install ports /usr/ports/devel/p5-Term-ReadKey and /usr/ports/comms/p5-Device-SerialPort or install the packages containing them.
For OSX the first place to look is the Apple Store.

Alternatively, you can find these modules at CPAN. Installing modules from CPAN requires administrator rights as well as some familiarity with make and install procedures. You will find detailed information for your operating system here and here.

Windows.

On Windows the Perl interpreter will usually not be installed. Check that using menu-option 'Run' or a DOS-box (cmd.exe) with perl -v. An interpreter for Windows can be found at the Perl website. One more Perl module is needed, Win32::SerialPort (for both 32-bit and 64-bit Windows). Activestate Perl is recommended. It is easy to install and comes with a module manager that allows you to install Win32::SerialPort. In the giant list of additional modules you will find SerialPort under 'CPAN'. If you already installed another Perl version you can download the module from CPAN. Please take a look at the installation instructions mentioned above first.

It is best to do all installation and configuration work as root/administrator. Normal users may not have the rights necessary to install software or to access serial ports. Once it all works it is easy to find out which rights are needed for the average user.

The cable.

Common serial computer cables (straight or cross) won't work. That's because the Studer pin layout deviates from the norm in the computer world. Hence you need to make a custom cable. You might use an old computer cable for that, but you will have to solder a new connector to at least one end. The recorders work with RS-232 without hardware flow control, which means that basically only 3 wires are needed: TX (transmit data), RX (receive data) and ground. These are the blue wires in the pictures.
For Studer machines the cable should be like this:

For the Revox models C270, C274 en C278 the cable should be like this:

For Revox: Here pins 2 (ground), 3 (tx, transmit data) and 4 (rx, receive data) of the male DIN-plug for the tape deck must be connected to pins 5 (ground), 2 (tx) and 3 (rx) respectively. These are the blue wires in the picture. The metal shielding of the cable, if it is there, can be soldered to the metal casing of the connectors (the black wire in the pictures). It is not necessary for operation, but in case of very long cables (50 feet or more) it is recommended. A warning to C27n owners: Pins 6 and 7 in the DIN-plug carry resp. 24 volts and ground for a remote control. Make sure these pins remain properly isolated.

The blue wires are basically all that is needed for serial communication. However, with a few laptops it would only work when we connected (bridged) pins 4 (DTR) and 6 (DSR). It is the green wire inside the computer connector. Some computers seem to insist on the use of hardware flow control, even if it is not available at the counterpart (the tape decks don't have pins for DTR and DSR). So depending on your hardware this green wire may be needed as well. Adding it doesn't harm. The tape decks don't do hardware flow control, to the computer the green bridge merely simulates a 'ready-to-send' signal from the counterpart.

Some people ask whether we see the front side or the soldering side of the connectors here. It is the front side, not the soldering side. It doesn't really matter. Both Sub-D and DIN-connectors will always have the pin numbers printed on the soldering side, sometimes on both sides. These pin numbers are always leading.

You can check the cable with a loopback test. For that to work, you need to bridge the pins 2 and 8 of the plug for the tape recorder. See the photo on the right. At program start, the Perl script will show Receiving exactly what was sent.Is a loopback device connected?. It means that you selected the right comm port and that the cable works well.

The Perl script.

May 2018: Version 2.0 is ready. Several bugs fixed concerning flow control (xon/xoff) and local echo. For the human-readable list with audio parameters the Motorola 'D' and 'P' commands were replaced by 'AP?'. The latter will be slower but is supported on more models and software versions. Furthermore many improvements and additions for OSX and the A820. Thanks to Jacob Korn for his support. Jacob works on reviving analogue synthesizers by making them accessible through MIDI. Definitely worth a visit.

A configuration file and the script itself. Two versions, one for Linux, FreeBSD and OSX (with LF line ends) and one for Windows (with CR/LF line ends). Right click on the link and choose Save to download the files. Both files can be viewed and edited with any text editor.

Linux, FreeBSD, OS X:

Windows (32 en 64 bits): You can find information on how to use the script here.
 



Last update: May 30, 2018.