MIDIbox Hardware Platform, Digital OUT Module

The DOUT module comes with multiple serial registers 74HC595; every register provides 8 digital outputs, which are updated with the latch enable signal RCLK and shifted out with the clock signal SCLK. The advantage of using such shift registers is, that they can be cascaded to a long chain without the need of more than 5 cables to the core module. The DOUT board has been designed on a way which allows to cascade not only the ICs on the board, but also several DOUT modules. But note that it depends on the firmware how much outputs are processed by the core module:

  • MIOS8 based applications typically allow to cascade up to 4 modules (=16 DOUT SRs), makes up to 128 digital outputs
  • MIOS32 based applications typically allow to cascade up to 8 modules (=32 DOUT SRs), makes up to 256 digital outputs

Some applications also allow to scan the shift registers in a so called "matrix" configuration. E.g. a 8x8 matrix (which is driven by a two DOUT SRs) can drive up to 64 LEDs, a 16x16 matrix could drive up to 256 LEDs. But normally 8x8 matrices are perferred due to higher duty cycle: 8x8 matrices make LED visible at 12.5% of the time which is normally bright enough, 16x16 matrices make LED visible at only 6.2% of the time which is mostly too dark!.

Please note: due to historical reasons, the "first LED" is usually located at D7 of an output connector, while on a MBHP_DIN module the "first button" is located at D0 of an output connector. See also this Wiki page. This might be confusing, on the other hand changing these assignments for newer MIDIbox projects might confuse users even more! Therefore please bear with me that this assignment won't be changed anymore (it also has layout advantages)!


Note: To reduce effort only the DOUTX4 variant is available at Mikes PCB shop and SmashTV's MIDIbox Shop. If you don't want to etch the modules by yourself, just use the DOUTX4 and stuff just only the ICs which are really required.

PCB data, can be viewed, modified and converted with Eagle Light. The .pdf based schematic has been created with xcircuit. There are no special eagle schematics available, since components have been netlisted in the .brd file directly!
Module Schematic Layout Data (old PCB) Quick-view (old PCB)
MBHP_DOUTX4_V1 mbhp_doutx4.pdf mbhp_doutx4_v1.brd mbhp_doutx4.gif
MBHP_DOUTX3_V1 mbhp_doutx3.pdf mbhp_doutx3_v1.brd mbhp_doutx3.gif
MBHP_DOUTX2_V1 mbhp_doutx2.pdf mbhp_doutx2_v2.brd mbhp_doutx2.gif
MBHP_DOUTX1_V2 mbhp_doutx1.pdf (normaly built on veroboard) (normaly built on veroboard)
MBHP_DOUT_MTC_V1 similar to DOUTX4 mbhp_dout_mtc_v1.brd mbhp_dout_mtc.gif
Module Schematic Layout Data (revised PCB) Quick-view (revised PCB)
MBHP_DOUTX4_R5 mbhp_doutx4_r5.pdf ask SmashTV mbhp_dout_r5_detail.jpg
Additional informations
File Size Description
mbhp_doutx4_orderlist.txt 1k Reichelt orderlist for old layout
mbhp_doutx4_r5_orderlist.txt 1k Reichelt orderlist for SmashTV layout
mbhp_doutx4_32leds.pdf 16k How to connect 32 LEDs (old PCB)
mbhp_doutx1_reed_relays.pdf 9k How to connect Reed Relays to a DOUT module (old PCB) - see also this photo
mbhp_doutx4_ledrings.pdf 31k How to connect 16 LED-rings (old PCB)
Note: a 16x16 LED matrix configuration leads to bad LED brightness - a 8x16 matrix configuration is recommended today!
mbhp_doutx4_mtc.pdf 12k How to connect 8 LED-digits for the MTC display of MIDImon (old PCB)
mbhp_dout_8x8leds.pdf 18k How to connect a 8x8 LED matrix (new PCB)
mbhp_dout_8x16leds.pdf 18k How to connect a 8x16 LED matrix (new PCB) - can also be used for LED rings (8x16 matrix is recommended instead of 16x16 for best brightness)

Available Ports

Following interfaces are provided by the DOUTX4 module:

The revised PCB layout from SmashTV uses 2-row DIL headers instead so that buttons can be easily connected via 2-row DIL sockets.
Name No. of pins Description
J1 5 Interface to CORE:J8 (if LEDs are used). DOUTX4:J1 provides two power pins for 5V/0V, the serial clock, the latch enable and the serial input of the register chain.
This port can also be connected with J2 of another DOUTX module.
The revised PCB layout from SmashTV uses a 2-row DIL Header instead to simplify the connection to the J8/9 connector of the core module.
J2 5 Interface to another DOUTX4 module. DOUTX4:J2 provides nearly the same pins like J1, just only the serial input of the first IC is replaced by the serial output of the last IC.
This port can be connected with J1 of the next DOUTX module.
J3-J6 5 These are the digital output lines, every connector comes with 8 of them and an additional pin for ground. See mbhp_doutx4_32leds.pdf as an example how to connect LEDs to these pins, and mbhp_doutx4_ledrings.pdf how to connect LED rings.

Used Components

Part Name Value Description
IC1, IC2, IC3, IC4 74HC595 The digital output shift registers
R1-R32 220 These resistors are required if LEDs should be driven with the output, just to limit the current through the LEDs. If you are using the DOUT module with a MIDIO128, and would like to drive additional logic chips instead of LEDs, these resistors are not required and can be replaced by bridges.
If the module is used to drive the LED-Rings of MIDIbox16E, R1-R16 have to be replaced by bridges, see also mbhp_doutx4_ledrings.pdf
C1-C4 100nF The additional bypass caps have to be placed on the bottom side of the PCB, as close to the +5V power input of the 74HC595 as possible.
J* * All connectors are optional, the cables can also be soldered directly into the board. Otherwise I suggest SIL headers (header sockets), known from PC motherboards. They are cheap and usefull.
DIL SOCKETS Don't forget to buy sockets for the shift registers. 4 * 16 pin DIL sockets are required for the old PCB layout, resp. 4 2x5 DIL sockets for the SmashTV layout.

Soldering Guide

This soldering guide explains how to build a DOUT module based on the revised layout from SmashTV. If you want to build a DOUT module based on the old layout (e.g. from Mike) please continue at this page.

It's always a good idea to start with the smallest components to simplify mounting.
So, start with the caps:
  • C1-C4: 100 nF
Continue with the 4 IC sockets.
And then solder the resistors - here I'm using the nice 8x220 Ohm arrays (which look like ICs). Unfortunately they are only available at Mouser (652-4116R-1LF-220). Alternatively mount 32 discrete 220 Ohm resistors (not shown here).
Thereafter mount the 2x5 SIL headers. As you can see, we are using "polarized" headers for J1 and J2, and DIL headers for J3-J6, so that the silkscreen (which shows the pin names) won't be hidden. It's your personal choice to use "polarized" headers for these connections as well.
Finally put the 74HC595 ICs into the sockets. Your module is now ready for use!

Two cascaded DOUTX4 modules connected to J8/9 of a MBHP_CORE_STM32F4 module with selfmade IDC cables.

Two cascaded DINX4 and two DOUTX4 modules connected to J8/9 of a MBHP_CORE_STM32F4 module with selfmade IDC cables.
This picture gives you a more detailed view of the special (selfmade) Y cable which has one additional DIL socket at the middle so that the DIN and DOUT chain can be connected to the J8/9 connector of the core module.

Last update: 2016-05-22

Copyright 1998-2016, Thorsten Klose. All rights reserved.