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MIDIbox SEQ V4

User Manual --- Hardware Options

This page discusses various hardware options which are provided by MIDIbox SEQ V4.

USB MIDI

Thanks to the integrated USB peripheral of STM32, USB MIDI is natively supported by the firmware. This simplifies the upload of new firmwares, and speeds up MIDI transfers to your DAW and/or virtual synthesizers up to 100 times and more - see also this forum article.

The sequencer will also run without USB of course. Two MIDI IN and MIDI OUT ports are provided by the MBHP_CORE_STM32 module for connecting MIDI devices such as synthesizers, drum machines, Fx gear, keyboards, etc.

Power Supply

The power consumption of a common MIDIbox SEQ V4 configuration is about 400..1000 mA depending on the used LCDs and LEDs. Especially blue backlights and LEDs can increase the consumption dramatically!

It's recommented to supply the MBHP_CORE_STM32 module from an external PSU (e.g. a wall adapter) connected to J1. Jumper J17 (USB Power Option) has to be disconnected in this case!

Alternatively MIDIbox SEQ V4 can be powered from the USB port (PSU removed from J1, J17 jumper connected) if an USB hub with external power supply is used.

SD Card

A SD Card is required as data storage for patterns, songs, grooves, options, the hardware configuration, MIDI files, SysEx dumps and various other files. It obsoletes the BankSticks which were used in previous MIDIbox SEQ versions due to many advantages: cheaper, much more data can be stored, easy availability (even in supermarkets), easy data exchange/backups with a computer.

The MIDIbox SEQ V4 firmware provides an integrated SD Card Reader function via USB which gets use of the Mass Storage Device (MSD) protocol, so that the SD Card can be mounted from your operating system (Windows/MacOS/Linux/etc...) without the need for a driver installation. The MSD mode has to be activated in the Disk menu (press Utility->Disk). It overrules the USB MIDI driver, which will be available again once the SD Card has been unmounted from the operating system.

Thanks to this useful feature, it's possible to build the SD Card into the case (no need for an external socket).

If you've the choice, buy a SD Card with speed factor 100x or more - it directly affects the access time to files. A speed factor of less than x60 is not sufficient for the realtime requirements (e.g. while changing patterns), the sequencer could sporadically block for a couple of mS which can result into temporal hang-ups.

SD Card size: typically only ca. 5 MB are allocated by MBSEQ_* files. The remaining disk space can be used for storing backups, SysEx dumps and MIDI files, but probably never more than 50..200 MB will be used. Accordingly, a 256MB or 512MB card is already sufficient. Using a 1, 2 or 4 GB card is great but not really required. Sizes > 4 GB are *not* supported by the file system (FAT32) anyhow, and therefore not recommented.

Pots or Encoders?

MIDIbox SEQ V4 only provides an user interface with 16 rotary encoders (endless knobs) + 1 data wheel (the 17th rotary encoder).

Analog pots are not supported. The reason: pot control might sound like "vintage", "old style" and "analog sequencer", and possibly could imply that pots are the best solution for perfect sequences, but this is just a popular fallacy and nothing else! In fact pots are only useful for sequencers which are controlling the analog gear directly, but for a MIDI sequencer you defenitely want to have features like "total recall" and "jumpless switching" between tracks, layers and patterns.

In addition, the menu pages of MIDIbox SEQ V4 rely on rotary encoders more than before. MIDIbox SEQ has a flat menu hierarchy, and this requires that all values can be changed directly - with the 16 rotary encoders.

Inc/Dec Buttons or Datawheel?

For the menu navigation and data entry either Inc/Dec (Up/Down) buttons and/or a datawheel can be used. The datawheel (rotary encoder with big knob) should be the preferred solution since it simplifies the selection of parameters with a wide value range (like BPM).

If you are planning a new frontpanel, it even could make sense to consider both - datawheel and Inc/Dec buttons, because buttons are sometimes better for finetuning parameters. The Fwd/Rew buttons can be used for the same purpose by default, but only as long as the Song mode is not active.

Detented or Non-Detented Encoders?

In difference to suggestions for MIOS based MIDI controllers, for MIDIbox SEQ I strongly recomment detented rotary encoders! Of course, MIOS provides three types, and all are working. But for a sequencer, where you want to select the notes exactly and not "smoothly", detented encoders are really the preferred ones.

Note that there are three different types of detented rotary encoders (see also this Wiki page). The MBSEQ_HW.V4 file (stored on SD Card) has been preconfigured for "DETENTED2", which is the most commonly used (encoders provided by Voti/SmashTV). If you notice, that your encoders only work in one direction, please change the type to "DETENTED1" or "DETENTED3" at the bottom of the setup file.

How many buttons?

If you are building a new MIDIbox SEQ it's highly recommented to mount at least the buttons which are used in the original V3/V4 design to ensure best ergonomic handling. This means, that you want to use at least 44 buttons!

With MIDIbox SEQ V4, some new button functions have been introduced, which should be considered on new frontpanel layouts. These are:

• Group Select Button 1/2/3/4: Four buttons which provide a direct access to the four track groups. In combination with the four track buttons, this allows you to change between the 16 tracks quickly.
  With the MBSEQ V2/V3 frontpanel, the track group has to be selected with the F4 button.
• Trigger Layer A/B/C: Three buttons which provide a direct access to the trigger layers.
  With the MBSEQ V2/V3 frontpanel, the trigger layer has to be selected with the F3 button.
• Step View: Changes to the Step View selection display.
  With the MBSEQ V2/V3 frontpanel, the step view has to be selected with the F2 button.
• Utility: changes to the Utility page, e.g. to access the Copy/Paste/Clear function.
  With the MBSEQ V2/V3 frontpanel, the Utility page has to be selected with the F1 button.

Note that there is also a MIDI Remote feature available which allows you to trigger button functions with a MIDI keyboard. However, the handling isn't so perfect like with dedicated buttons (especially since the LEDs are missing on a master keyboard), but it works!

It isn't required that the buttons are assigned to the same DIN input pins like predefined in the MBSEQ_HW.V4 file (stored on SD Card). You are able to change the pinning for your (existing) hardware. But if you want to keep it compatible, then use exactly the same pinning like me.

DIN Pinning of hwcfg/standard_v4/MBSEQ_HW.V4

How many LEDs?

Some button functions require a LED as some kind of feedback which is not given by the LCD. For example, the selected Track and Layer is not always displayed by the LCD, also Solo/Fast/All and especially the played (unmuted) steps.

This means that you want to have at least 30 LEDs. One additional LED can be added as beat indicator.

With MIDIbox SEQ V4, some new LED functions have been introduced, which should be considered on new frontpanel layouts. These are:

• Group Select LED 1/2/3/4: to display the selected group
• Trigger Layer A/B/C: to display the selected trigger layer
• 16 Bicolour GP LEDs (Red/Green): improve the visualisation of the current step position

Also LEDs for Play/Stop/Pause are available now. These LEDs have been requested, but if you ask me: they are not required...

DOUT Pinning of hwcfg/standard_v4/MBSEQ_HW.V4

Simple 4x16 Button/LED matrix

By default the 16 "general purpose" LEDs (which belong to the 16 "general purpose" buttons) display the triggers of the current selected track. If the sequencer is running, they also display the current sequencer position by inverting the appr. step LED.

MIDIbox SEQ supports an option to handle 64 LEDs for all 4*16 steps of a pattern (which consists of 4 tracks). This option requires just 4 additional DOUT pins which are driving the cathodes of the LED rows.

It's even possible to use Duo-Colour LEDs, so that the step pointer gets an individual colour (no inversion of the active step required)

Another hardware option allows to use 64 instead of 16 GP buttons, or, to use the 64 buttons in addition to the 16 GP buttons.

All possible options, and the appr. settings are described in the MBSEQ_HW.V4 file of the release package.

Pinning of Button/Duo-LED matrix (Note: circuit needs to be improved for high-current LEDs!)

I built such a Button/Duo-LED matrix as some kind of "breakout box" for my MIDIbox SEQ, which sits on top of the sequencer - pictures. WARNING: there is no premade PCB available - design not recommented for beginners!

Giant 16x16+X Button/LED matrix

The most flexible and probably also most preferred BLM solution, as it provides much more entry modes.

PCBs will be created by the community!

More informations, schematics and videos are available in a special manual chapter.

Which display size?

For MIDIbox SEQ V4, two 2x40 LCDs are required! The menu pages won't be displayed completely on smaller LCDs, a software solution for 2x16 or 2x20 LCDs is not supported (and very hard to realize)!

A single 4x40 LCD as replacement for the two 2x20 LCDs is possible, but keep in mind, that this requires to arrange the GP buttons and rotary encoders at the top and the bottom of the LCD, so that they are aligned with the 8*5 character segments of the display. Without this alignment, menu item values cannot be edited intuitively.

BPM LED digits

Optionally MIDIbox SEQ can be stuffed with 3 LED digits which display the current BPM value. Note that this only works in master mode, in slave mode SLA will be displayed instead. LED digits with common anode or cathode are supported. They are driven time multiplexed, and have to be connected to two dedicated shift registers like documented in this schematic.

MBHP_IIC_MIDI modules

Up to 4 MBHP_IIC_MIDI modules can be added if desired (note: with a simple hack in the IIC firmware even 8 modules could be accessed from the sequencer - infos available on request).

Main advantage of multiple MIDI ports is reduced latency (as MIDI events can be sent in parallel), and relaxed MIDI channel handling (for 4 synths you don't need to take care about the MIDI channel at all)

The MIDI IN port is not supported, accordingly the "OUT only" version is sufficient.

Following diagram shows the module interconnections.

The modules will be detected by the MIDIbox SEQ application automatically during startup. "Hot plug&play" while the application is running is not supported.

CV Outputs

MIDIbox SEQ V4 can control up to 8 analog outputs by connecting an MBHP_AOUT or MBHP_AOUT_NG module, or up to 4 MBHP_AOUT_LC modules to the core.

Up to 8 digital triggers (gates) are available at J5A/B of the core module. They have to be enabled with J5_ENABLED set to 1 in MBSEQ_HW.V4 (default). The output voltage is only 3.3V - if 5V triggers are required, a 74HC541 can be used as level shifter:

• Pin 1 and 19: OE# connected to ground
• Pin 10: to ground as well
• Pin 20: to 5V
• Pin 2..9 are the inputs (connected to J5A/B)
• Pin 11..18 are the outputs (connected to your synth gear)

For those who cannot get enough, 64 additional drum triggers are available in the DOUT chain. They can be controlled with individual key numbers and trigger a pulse of 1 mS. The used DOUT shift registers have to be defined in the MBSEQ_HW.V4 file (DOUT_GATE_SR1..8)

Tracks can be assigned to the outputs in the MIDI event menu. It's also possible to route incoming MIDI events to the AOUT/gate triggers in addition (this replaces a CV interface completely). The AOUT channel and trigger routing is described in the "Special Pages" chapter of the User Manual.

Ethernet Interface

The usage of MBHP_ETH is under preparation to support the OSC protocol natively without the need for a computer based proxy.

First performance tests show good results, but USB transfers are still faster. The advantage of OSC compared to USB MIDI is the higher flexibility, especially when applications running on multiple computers should be accessed. Even wireless communication in a WLAN network is possible if the MBHP_ETH module is connected to a WLAN bridge.

Latest update: the ethernet option is available since Beta24

Hardware costs

Here a list of a common "MIDIbox SEQ V4" setup - you can reduce the costs by choosing cheaper buttons, a cheaper case/panel and by organizing bulk orders in the MIDIbox Forum!

Note that premade PCBs can be purchased at http://mbhp.avishowtech.com (SmashTV). They also purchase complete kits for the modules and some of the other parts (like rotary encoders).

Prices and ordering numbers are from Reichelt if not specified. A list of alternative electronic shops outside germany can be found in the Wiki

Complete kit (?)

A kit for a complete MIDIbox SEQ isn't available, but thanks to joined efforts in the MIDIbox community it never was so easy to build a superior looking sequencer!
Have a look at:

• Wilba's Frontpanel: a PCB which replaces the DIN and DOUT modules. All buttons, encoders and LEDs are directly mounted on the PCB together with DIN/DOUT shift registers.
• Bulk order section of the MIDIbox forum - organize group buys to save money for special parts
• MIDIbox SEQ section of the MIDIbox forum - search and/or ask there if anything about the hardware is unclear. We are also interested in reports about how you built your sequencer, where you ordered the parts, etc.!

Copyright © 1998-2010, Thorsten Klose. All rights reserved.