2024-02-03
#music #electronics

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+ + + +

RBUS-ADAT User Manual

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+This version of the manual is for revision 1 of the board. +Copyright Chris Xiong 2024. Copying of this hardware and its design as well as this documentation is permitted +under the terms of CERN-OHL-P v2. + + +

+

1 Preface

+

If you are reading this, chances are you have become an unfortunate test subject of the RBUS-ADAT conversion +board (or have the nerves to think about becoming one). Well, here is (almost) everything you will want to know +about the board. If you want to learn about some less useful information about this thing, consider checking out +the devlog, which can be found by following the link to the project homepage listed under “Useful +links”. +

As this manual is written as if it’s a blog post, which is prone to being very rambly, I’ll try to keep the rambling +low, at least make an attempt to do so. +

Pictures in this manual are renders (computer-generated) and are for illustration purposes only. +

This product is neither affiliated with or endorsed by Roland Corporation. Roland does not approve +connecting unofficial accessories to proprietary Roland interfaces. +

Visit chrisoft.org/rbusif for any future updates to this manual and the hardware. + +

+

2 NO WARRANTY

+

THIS BOARD IS HOMEBREW AND EXPERIMENTAL HARDWARE. THERE IS NO WARRANTY FOR THIS +HARDWARE, INCLUDING ITS DESIGN AND THE FINISHED PRODUCT, TO THE EXTENT PERMITTED BY +APPLICABLE LAW. THE DESIGNER SHALL NOT BE HELD LIABLE FOR ANY DAMAGE CAUSED BY USING +THIS HARDWARE, UNLESS REQUIRED BY APPLICABLE LAW. +

For the full legalese text on warranty and liability, please refer to the license text. +

If this board fried your equipment, don’t try to extract anything from me. That’s what this section is trying to +say. + +

+

3 Open hardware

+

This board is open hardware licensed under the CERN Open Hardware Licence Version 2 - Permissive +license. Feel free to make as many of this board as you wish and sell them, as long as your follow the +terms. +

Contributions welcome and will be appreciated. If you have any suggestions to improve the board, +please feel free to contact the author. The author’s contact information can be found on the project +homepage. + +

+

4 Safety notice

+

There’s no enclosure for this board. As a result there would be exposed conductors on both sides of the board. +You’re advised to take measures to prevent them from shorting out. You may try any combination of the +following: +

+

+
Placing the board on an non-conductive surface. +
+
There are two M2 mounting holes in the board. Using two M2 screws and nuts, install a plastic sheet + (or cardboard even) under and / or over the board. + + +
+
Don’t use the board at all. Don’t even think about it.

+

Again, if you fried your equipment while using this board, it’s all your fault. I mean not really – I would still +want to know what happened. But it’s all your fault. + + + +

+

5 Intended usage and applicable devices

+

RBUS-ADAT is designed for use with the Roland XV-5080. It converts the 8 digital outputs exposed by XV-5080’s +R-BUS port to a standard ADAT lightpipe stream which can be recorded with any audio interface with an ADAT +input. +

The ADAT output from this converter is 20-bit and has the same sampling rate as the input supplied from the +R-BUS port. +

This converter cannot: +

+

+
Convert ADAT back to R-BUS input. i.e. you can’t record an ADAT stream on a V-Studio through + R-BUS with this converter. +
+
Serve as a clock source for the connected R-BUS device. You should always select “internal” as the + clock source for the connected R-BUS device. +
+
Expose the MIDI interface on the R-BUS port.

+

The converter is designed and tested with the XV-5080. In addition, the only audio interface that +has been verified to work is Focusrite Scarlett 18i8 3rd gen. I don’t have the resources to test other +devices. +

The converter has not been tested against VM- or VS- devices that feature RMDB 2 / R-BUS ports +or MV-8××× fitted with the MV8-OP1 expansion but may still work as a unidirectional converter +as intended. If you decide to try this converter with these devices, reporting the results would be +appreciated. +

The converter is not compatible with devices with the older RMDB port. + +

+

6 What’s on the board

+

+
R-BUS DB-25 Connector. See “Choosing a suitable cable” for what you should and shouldn’t plug + into this connector. +
+
Power indicator. Illuminates if the board is receiving power. + + +
+
ADAT Lightpipe output. Connect to a device capable of recording ADAT data stream with a + TOSLINK cable. +
+
Pure hecking magic.

+

7 Quick start

+

+
Using a suitable cable (see the following chapter), connect the R-BUS DB-25 connector on the board + to the R-BUS port on your Roland device. +
+
Connect the ADAT output on the board to the ADAT input of your recording equipment with a + TOSLINK optical fiber cable. +
+
Turn on the Roland device, then turn on your recording equipment.

+

8 Choosing a suitable cable

+

DO NOT USE ROLAND’S OFFICIAL R-BUS CABLE!!! +

Please use a straight through DB-25 male-to-male (pins on both ends) cable to connect the R-BUS port on your +device to the port on the converter. These cables connect pin 1 to pin 1, pin 2 to pin 2, pin 3 to pin 3 +etc. These cables are usually sold as “DB-25 RS-232 serial cable”. Do NOT use any of the following +cables: +

+

+
Roland’s official R-BUS / RMDB 2 cable +
+
Parallel port cable +
+
SCSI cable +
+ + +
LPT port Printer cable +
+
Null modem cable

+

These cables all use the same DB-25 connector but are wired differently. Using the wrong cable may damage the +converter and / or your device. +

Note that many RS-232 serial cables designed for relatively newer computers use the DE-9 connector. You’ll +need the older style with DB-25 connectors (which conveniently have 25 pins). +

DO NOT USE ROLAND’S OFFICIAL R-BUS CABLE!!! + +

+

9 Notes

+

+
Digital recording made from Scarlett 18i8 of the converted ADAT stream seem to have the full 24-bit + resolution. However this might be due to interpolation done by the audio interface or the operating + system. I do not have proper equipment to verify the bit depth of the output data stream. As such, + only 20 bits out output resolution is guaranteed. +
+
The optical output port is a tight fit. You have to insert the plug all the way in until you hear a click.

+

10 Specifications

+

+ + + + + + +


Signal processing	24-bit internal, 20-bit output

Sampling rate	44.1 kHz, 48 kHz

Connectors	R-BUS (Input only): DB-25 Digital output: ADAT Lightpipe (JIS F05 connector)

Chipset	coolaudio V1401 (Alesis AL1401 equiv.)

Rated current	<8 mA

Rated power	<0.04 W

+

11 Appendices

+

11.1 Build instructions

+

This is intended for people who didn’t end up with a pre-assembled board. If you already have a fully assembled +board, you may ignore this section. +

If you have a kit, you may skip to step 3. + +

+

11.1.1 PCB production

+

I assume if you have chosen to take this route, you know what you are doing. + + +

You’ll find Gerber files in the out directory of the project repository that you can upload to your favorite PCB +production service provider. Or alternatively if you want to tweak the board you can open up the KiCad project +files, which are also found in the project repository. +

Many PCB manufacturers will add a board identifier to each PCB they make and allow customization of where +this identifier will be placed. The front side silkscreen text “Production ID” is reserved for this purpose. Please refer +to the ordering instructions of your PCB manufacturer for the details. Usually this will involve changing +the text to something specific to that manufacturer and selecting an option before submitting your +order. + +

+

11.1.2 Bill of materials

+

+ + + + + + + + +


Designator	Part	Qty

C1	16V 100μF electrolytic	1

C2, C3, C4	50V 0.1μF ceramic	3

CN1	Cliff FCR684208T	1

D1	1N4002	1

D2	Red GaAsP / GaP LED 3mm ^a	1

J1	Adam Tech DB25-SL-25 ^b	1

R1	1/4W 1kΩ	1

R2	1/4W 2.2kΩ	1

U1	SN74LS04N	1

U2	coolaudio V1401	1

+

11.1.3 Assembling

+

Again, I assume if you are assembling the board yourself, you possess the appropriate set of skills. It’s now time for +them to shine. Most components are through hole so it should be easy. If it’s not already obvious, solder the only +SMD chip first. + +

+

11.1.4 Testing

+

If you have a 5V power source, it is suggested to test your assembled board first. Supply 5V between the anode of +the D1 and the metal shell of the DB-25 connector (GND). Check if anything pops. + +

+

11.2 Useful links

+

+
R-BUS project homepage: https://chrisoft.org/rbusif +
+
Project repository for this board: https://cgit.chrisoft.org/rbus-adat.git +
+
Online version of this manual:
https://chrisoft.org/blog/post/rbus-adat-m.html (html version)
https://filestorage.chrisoft.org/blog/data/rbus_adat_m.pdf (pdf version)

+

11.3 Schematic

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+ + +

+

11.4 Circuit board

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Front side

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+ + +

Back side

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+ + +

^a5mm used in prototypes

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^bOr any right angle DB-25 receptacle with 8.1mm backset spacing

+ + +

+

Chrisoft

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