Custom Digital Control Unit



Custom Digital Control Unit

Digital Control Unit

Vadis was approached to provide a small, self contained, custom designed unit to power up, provide digital and I2C control and readback for a customer's DUT to facilitate the programming section of their DUT build process. Currently they use a full functional test system to perform this part of the build which is an inefficient use of resources and restricts when and where this programming can be performed.


The requirement specified a compact desktop unit capable of providing the following signal lines to/from the DUT.

  • Standard I2C communication
  • Static 3V3 digital control lines (Write & Read)
  • High speed 3V3 digital control (Write only)
  • DUT power via external PSU
  • Control and power status to be reported via LEDs situated on the unit top panel

A custom software package was needed to provide control over the external  programmable PSU, the static and high speed digital lines and the specific commands to communicate with the DUT devices on the I2C bus.


After the initial discussion with the customer to fully understand their requirements, Vadis developed a special to type unit based around a National Instruments COTs sbRIO FPGA board the sbRIO-9605. Internally the various digital lines from the FPGA are accessed with a National Instruments RMC NI-9694 breakout board which is wired to a Vadis designed buffer PCB which serves to protect and buffer the higher cost FPGA, plus facilitate the drive currents for the LED indicators. The custom PCB also provides through connection of the external benchtop PSU lines to power the DUT. Control of the interface unit is provided with a laptop via an EtherNET connection.

Running unique Vadis developed firmware both in the FPGA and on the real time processor the unit provides the static and high speed digital signals to control the DUT mode and active circuitry. The unit can then communicate with the programmable DUT circuitry via I2C to send standard commands to read and write EEPROM locations, programming various unit power up settings. Static control lines provide addressing and mode control with the high speed line being able to provide a pulse train with variable pulse duration (resolution 10ns) and duty cycle.

The final unit will be used in a cleanroom and production line environment and is housed in a metal box with the various input and output connectors either end. Specialist cables provide the connectivity to the external PSU and DUT.

Programmer ScreenshotSoftware was developed to provide both engineering level control over the individual signals, I2C command address and data plus go/nogo functionality for operator level program, test and verify. All written in LabVIEW by a certified engineer the solution is completely scalable with source code provided to the customer. The interface unit automatically boots with the required FPGA and RT code and is provided with a documented SCPI command stack implementing common SCPI command such as *IDN?, SYST:ERR?, RST etc. As well as the unit specific commands required for the unique functionality. This SCPI interface means the customer can if desired repurpose the unit to provide this functionality as part of a bigger system by writing test code implementing the commands required.

If you have a project like this you would like to discuss please call us on 0330 113 7966 or email us This email address is being protected from spambots. You need JavaScript enabled to view it.