The Duex4 was developed by Tony from Think3dPrint3d in conjunction with RepRapPro. It adds a further 4 stepper, heater and endstop channels to the Duet 32 bit electronics allowing for a total of 9 stepper channels and 7 heater channels.
The Duex4 has 2 versions, the original version as described in this blog post, and the version 2a as described here.. The main difference between the original version and the version 2a is the addition of analog ground to reduce the noise on the thermistor readings.
The Duex4 hardware design is licensed under the CERN OHW License 1.2: the design is free to be distributed and modified within the terms of this license. All the design files are available on Github. The Duet was completely designed using the Open Source software package KiCAD so hacking and building on this design is accessible to all.
This is the same file as on the Duet page
The pinouts are on the back of the board, a KiCAD export shows the back below for reference (this is the view from the bottom of the board, so is mirrored):
Note that the board is labelled with E1 to E4 which applies to the Duet 0.6 with only 1 extruder on the main board (E0). When used with the Duet 0.8.5, which has two extruders on the main board (E0 and E1) the Duex4 provides E2,E3, D4 and E5. To maintain backward compatibility E5 is now in the slot labelled E1.
The detailed information on the pinouts is available on the Duet pinout page
Size 123 x 77.4mm, hole spacing 115 (input), 116.9 (output) x 61.23mm The 50way input header is directly in line with the 50way expansion header on the Duet.
The export from KiCAD shows the board and hole dimensions:
The Duex4 2a has a jumper that allows the source of analog ground to be selected:
The pictures here shows a flylead connected which is required for Duet 0.6, for Duet 0.8.5 a simple jumper is all that is required.
Wiring and Pinouts
Other than no VSSA jumper being present, the wiring is the same as the Duex4 v2a.
Same as 0.2a