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GM5x5x5 Module


This page is dedicated to nILS' standalone GM5 USB-To-Midi PCB. All information present on and files linked to from this site is

© 2008 nILS Podewski. Free for private, non-commercial use. All other rights reserved.

Related pages:

PCB revisions

  1. Prototype: Green PCB
  2. Bulk order #1, revision 1.0: White PCB
  3. Bulk order #2, revision 1.1: Red PCB

PCB overview

The PCB is 8.8 x 1.925 inches (~22.4 x 4.9 cm) looks like this:

(click for full size)

A .pdf version is available here

A .pdf version with both layers visible is available here


NameNumber of pinsDescription
J1 4USB connector
J2 2+5V in-/output
J4 4Interface to a core modules J4 port. Serves as an in-circuit programmer for the EEPROM - only use this port, when the gm5x5x5 is not plugged into a USB port
J8 2Configuration Jumper. Closed (default): configuration, open: configuration
S1, S2, S3 2Configuration jumpers. See table in the schematic on or check the silkscreen. If you are not using an EEPROM you must set jumpers here, otherwise the gm5 will not be initialized properly
IN1 – IN5 3 (2 used)MIDI In Jacks (opto isolated), both available as 1×3 pin header and DIN5 socket
OUT1 – OUT5 3MIDI Out Jacks, both available as 1×3 pin header and DIN5 socket
IO5 2Digital MIDI IO (mainly for development)
USB POWER OPTION2Configuration jumper. Closed (jumper mounted): gm5 powered by USB (recommended). Open (no jumper mounted): gm5 powered by +5VDC via J2

Part list / BOM

Note that some resistor designators have changed in revision 1.1!

lead spacing
Part #
Crystal 16Mhz 1 HC18/U Q1
LED 3mm - 11 - LED1 – LED11
Diode 1N4148 5 - D1 – D5
Optocoupler 6N138 5 DIP 8 IC8 – IC12
GM5 GM5 1 TQFP32 IC1
Hex inverter(*2) 74HC14 5 DIP 14 IC3 – IC7
USB Type B socket - 1 - J1
DIN 5 (MIDI) socket - 10 MAB5SH IN1 – IN5, OUT1 – OUT5
3-pin SIL header - 10 100 milIN1 – IN5, OUT1 – OUT5
2-pin SIL header - 5 100 milJ2, J8, S1 – S3
Resistor (PCB rev 1.0) 220 Ohm 15 0207 R1 – R3, R6 – R8, R11 – R13, R16, R18, R31 – R33, R39
Resistor (PCB rev 1.1) 220 Ohm 15 0207 R1 - R3, R6 - R8, R11 - R13, R16 - R18, R31 - R33
Resistor (PCB rev 1.0) 1k Ohm(*1) 18 0207 R5, R10, R15, R17, R20 - R30, R35, R38, R40
Resistor (PCB rev 1.1) 1k Ohm(*1) 18 0207 R5, R10, R15, R20 - R30, R35, R38 - R40
Resistor 27 Ohm 2 0207 R36, R37
Resistor 4.7k Ohm 5 0207 R4, R9, R14, R19, R34
Polyfilm/Ceramic cap 100nF 6 200 milC2 – C7
Electrolytic capacitor 10uF/16V 1 100 milC1
Ceramic capacitor 22pF 2 100 milC8, C9
Ceramic capacitor1uF1100/200 milC10
Jumper - 5 100 mil-

(*1) Note that 11 of the resistor listed as 1k in the above list (R21 - R30 and R40) are for the LEDs. The values for these resistors depends on the color of LEDs you plan to use and the brightness you wish to achieve. Suggested values:

LED colorValue

(*2) The inverters can be left out when no status LEDs are needed. Leaving them will require soldering some additional bridges which will be described in a section in this document later on.

Don't forget to order 6 DIP8 and 5 DIP14 IC sockets and pin headers (16 pins total).

Hardware Options

The pcb was designed to allow for various options:

1. Different numbers of IOs

You can use the jumpers S1-S3 or the EEPROM to select the number of devices the gm5 will run. If you decide to go with less than 5, you do not have to mount all the parts. The list below tells you which parts you can leave out per MIDI port. Notice that if you are not using an EEPROM you have to correctly set the jumpers otherwise the gm5 will not initialize properly.

Port # not usedParts to leave out
5IC7, IC12, LED9, LED10, R16, R18, R19, R20, R29, R30, C7, D5, IN5, OUT5
4IC6, IC11, LED7, LED8, R11, R13, R14, R15, R27, R28, C6, D4, IN4, OUT4
3IC5, IC10, LED6, LED7, R6, R8, R9, R10, R25, R26, C5, D3, IN3, OUT3
2IC4, IC9, LED3, LED4, R1, R3, R4, R5, R23, R24, C4, D2, IN3, OUT3

2. (Not) using LEDs

If you want to use status LEDs, you will have to mount the 74HC14 hex inverters (IC3 - IC7) and the additional circuitry. If you do not want to use LEDs, you can leave out IC3 - IC7 and will have to add some jumper wires as follows. Instead of jumper wires you can easily use a 2-pin header and a jumper. Connect the following pins:

Port # without LEDsWires to add
5IC7:3 - IC7:2, IC7:10 - IC7:13
4IC6:3 - IC6:2, IC6:10 - IC6:13
3IC5:3 - IC5:2, IC5:10 - IC5:13
2IC4:3 - IC4:2, IC4:10 - IC4:13
1IC3:3 - IC3:2, IC3:10 - IC3:13

The additional LED circuitry can be left out of course, too:

Port # without LEDsParts to leave out
5IC7, R29, R30, LED9, LED10
4IC6, R27, R28, LED7, LED8
3IC5, R25, R26, LED5, LED6
2IC4, R23, R24, LED3, LED4
1IC3, R21, R22, LED1, LED2

Soldering info

All capacitors (except for the crystal bias caps) have a dual-footprint to allow for using 100mil or 200mil (2.54mm or 5.08mm) spaced capacitors. The image below shows how to mount either one. The first column shows the silkscreen you'll find for capacitors, while the second column shows the mounting position of 100mil (2.54mm) capacitors and the third column shows the mounting position of 200mil (5.08mm) capacitors.

Order lists

If you have an order list from a supplier that is not listed here, feel free to PM it to me, so it can be added to this page.

Reichelt12,37€;ACTION=20;LA=5010;AWKID=121145;PROVID=2084misses the 1uF capacitor!
Mouser12,42€ to frailn. Updated by Grizz
Allied Electronics$37.27GM5x5x5 - Allied Parts ListPut together by m00dawg

FAQ - Frequently Asked Questions

Q: Can I have the .brd or .sch file?

A: No.

Q: There are no ground connections. Why?

A: There is a ground plane on the bottom (blue) layer, which is not visible in the screenshot and .pdf.

Q: Can I leave out the inverters?

A: Yes, you can if you do not wish to have status LEDs. If you decide to do so, you will need to add some bridges to the board as described in the “hardware options” section.

Q: My gm5x5x5 isn't working - LED11 is lit and my computer doesn't recognize the device. What's wrong?

A: Most likely you forgot to put the jumpers S1 - S3 on the PCB. Put them on there (see jumper table for jumper positions), plug the gm5x5x5 back into the PC. Doesn't work? Check the soldering.

Q: Can you tell me the positions of the holes and sockets?

A: Sure. The following list has all the positions of the sockets and the holes. All measurements are in mil (1/1000th inch) and give you the center of component/hole.

Mount holes

USB socket (x)


Midi sockets (x)

gm5x5x5.txt · Last modified: 2017/09/05 08:42 by cavey