0x29: 16 ch A/D and 4 ch D/A converter Pi Top Module




The Pi Top is becoming a popular platform for software development using the Raspberry Pi singleboard computer. However, interfacing hardware to the Pi Top can be challenging, since the hub does not conform with the RPi GPIO header. This module enables easy measurement of up to sixteen voltages and generation of up to four voltage control signals.


This design features the popular PCF8591 8 bit 4 ch A/D and 1 ch D/A converter. Using, for instance, the wiringPi library, a convenient signal generation and measurement system can easily be developed and documented with this circuit board, e.g. for use in process control loops. Graphical user interfaces can be created using Qt and wiringPi. See the download section on this page for some example source code and the Qt tutorial for getting started.

License terms
The 0x29 design is published under the Creative Commons Unported 3.0 License.  I do not profit from this design, neither should you. You are welcome to adapt, modify, and redistribute this design as long as the license terms are respected.

Physical size of PCB

84 mm (width) by 56 mm (height). Double-sided.

Rendering and photos


DipTrace 3D rendering, frontside with components

DipTrace 3D rendering, backside with components 

0x29 module mounted in a Pi Top 2

Screen dump of Qt interface running on the Pi Top 2 (Polaris). Perfoming loopback test from D/A to A/D 


Bill of materials

8 pcs. decoupling capacitor, ceramic, 100 nF, 1206

4 pcs. capacitor, tantalum, 10 uF, 16 V, SMD (optional)

4 pcs. pullup resistor, 10k, 1206

2 pcs. BSS138 MOSFET, SOT-23

1 pcs. MCP1525 precision voltage reference, 2500 mV, SOT-23

1 pcs. MCP1541 precision voltage reference, 4096 mV, SOT-23

32 pcs. voltage divider resistor, 10k, 1206

1 pcs. jumper, 2.54 mm pitch

1 pcs. 2×4 way male header, 2.54 mm pitch

1 pcs. 3×16 male header, 2.54 mm pitch

1 pcs. 2×17 90 degree 2.00 mm pitch male header


Estimated cost

Components and circuit board should not cost more than EUR 10,-.



Schematic PDF: 0x29_schematic

DipTrace v. 3 schematic file: 0x29_schematic

DipTrace v. 3 PCB design file: 0x29_ratlined_public

Gerber files: 0x29_Gerber

Qt 5 GUI source code: QtGUI_0x29



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