Doepfer CTM64 Contact to Midi Interface (main board) - Manual (Page 9)

CTM64 Version 4 - User's Guide Page 9
Contact 1-64 (10) and Common (11)
The 64 contacts are connected to four double row pin headers with 16 pins each. 16 pin socket-
connectors (female) with flat cable can be connected to these pin headers (not included with the
CTM64). Additionally there is one common pin (11) for all contacts. Pay attention that only free contacts
can be used. This means that the contacts are not allowed to be connected with another electronics or
connected with a fixed voltage (e.g. GND).
The cable length has to be limited to a certain value. In accordance to the characteristics of the cable in
use capacitive and inductive effects deform the signal of the pulses that are used to detect a closed or
open contact on the common line (11). In this case closed contacts are no longer recognized or
accidentally only. From our experience cables up to 50 cm do not cause problems. For length between
50 cm and 2 m it depends upon the cable characteristics if the CTM64 will work as it should. Cables
longer than 2 m should be avoided. If long cables are essential relays have to be used. The relays are
located close to the CTM64 and the relay contacts are connected to the CTM64 like normal contacts.
Please pay attention to the warranty notes on page 1. Ignoring these notes causes warranty loss and
the right to return the goods.
Two different modes are available for the contacts: note on/off or program change. In the note
mode closing of a contact generates the corresponding MIDI note on message, opening generates note
off - both without velocity (velocity is fixed to 127). In the program change mode closing of a contact
leads to the corresponding MIDI program change message.
Jumpers 1-8 (12)
The CTM64 configuration (MIDI channel, mode, note offset) is defined with 8 jumpers. The jumpers are
put on the double row pin header JP5.
The jumpers 1-4 (next to the control LED) are used to set the MIDI channel.
Jumper 5 defines the mode (note or programm change).
In note mode the jumper 8 is used to select the note offset, i.e. the MIDI note number assigned to the
first contact (= contact no 1). Two different settings are possible: 0 or 36. 0 is the lowest note than can
be generated with MIDI. 36 is the lowest "C" on a standard 5 octave keyboard. Additionally the
jumpers 6 and 7 can be used to transpose one octave up or down (
±12 semi tones). Instead of the
jumpers 6 and 7 also a toggle switch with middle position (1-0-1 type) can be used. In this case the
terminals of the switch are connected to the corresponding pins of the double row pin header JP5.
Consequently the note offsets 0, 12, 24, 36 and 48 are available. In case that another note offset is
required the contacts are displaced correspondingly and the unused contact terminals are left free. If for
example a note offset 41 is required the note offset 36 is selected and the terminals 1-5 (corresponding
to the note numbers 36-40) are left open and the first contact is connected to terminal 6 (corresponding
to note number 41).
When the program change mode is selected the closing of a contact causes the transmission of a
MIDI program change message on the selected MIDI channel. In this mode jumper 8 sets the program
change offset to 0 or 64. Using two daisy-chained CTM64 with 64 buttons each the complete program
number range 0...127 is available. It is also possible to use a toggle switch instead of jumper 8 to
switch between the program number areas 0-63 and 64-127. The jumpers 6 and 7 have no function in
the program change mode.
Pay attention that there are 2 ways of counting of the program numbers: "1-128" or "0-127". If the
counting mode "1-128" is used one has to subtract "1" to obtain the corresponding program change
number in the counting mode "0-127". It depends upon the manufacturer of a MIDI device (synthesizer,
expander, sampler ...) if the counting "1-128" or "0-127" is used.