The microDXP miniaturized circuit-board can easily be incorporated into a variety of benchtop, portable, networked and embedded x-ray and gamma-ray spectroscopy data acquisition systems. In the first example the microDXP runs on the laboratory benchtop as a peripheral device. In the second example a more complex embedded system is considered. The I2C serial bus is used to control a ‘smart’ x-ray tube and detector HV bias supply, and the auxiliary digital I/O drives electromechanical or pneumatic components in real time based upon user defined metrics of acquired data.
Example 1. General-Purpose Spectrometer
In this example the microDXP and hardware included in the Development Kit act as a general-purpose digital pulse-processor, connected as a peripheral device under the control of a host computer. No specialized data acquisition modes are required, thus no firmware development is necessary.
XIA non-recurring engineering (NRE) required: None
User development required: Enclosure design
The microDXP, power supplies and microComU together constitute a digital pulse-processor that can be connected to virtually any controller with USB or RS-232 communications. Note: The microComU interface board included with the development kit falls into this category.
Fig. 1: A general-purpose spectrometer incorporating the microDXP. The microComU interface connects the microDXP to the host computer and power supplies.
Example 2. Dedicated Embedded Spectrometer
This example considers a materials sorting application where objects with certain pre-defined alloy ratios X, Y and Z are to be separated from others. An x-ray source irradiates incoming samples, and incident x-rays are collected by a solid-state detector connected to the microDXP. The microDXP is configured to assert a combination of its auxiliary digital I/O lines whenever the peak ratio X,Y, or Z is detected. The digital I/O lines drive electromechanical or pneumatic components in real-time to execute the appropriate mechanical operation, e.g. put the recognized object in the desired bin. User controls are limited to starting and stopping the system, and selecting one out of a small number of operating modes. Power supplies for the microDXP are also included. Finally, an external data port (e.g. RS-232) is also included so that ratios corresponding to new alloys can be defined, and new firmware uploaded without dismantling the hardware; or, alternatively, the microDXP could periodically be run in full MCA mode under computer control for diagnostic purposes.
This example demonstrates a system that uses a very small data acquisition command set (i.e. ‘start run’ and ‘stop run’) but that, conversely, requires customizations to the microDXP as well as significantly more user-designed hardware.
XIA non-recurring engineering (NRE) required:
- Customized PIC microcontroller code is required to implement the I2C peripheral device control.
- Customized PIC microcontroller code is required to implement high-level data acquisition routines controlledthrough the user pushbutton interface.
- Customized DSP code is required for peak ratio calculations, possibly implemented in lookup tables.
- Minimal FiPPI (FPGA) code modification is required to implement the auxiliary digital I/O functionality.
User development required:
- A more advanced interface unit is required to break out the microDXP high-density internal connection to standard RS-232, auxiliary and power connections. Still, this interface does not involve many active components, i.e. the I2C and auxiliary digital I/O are simply routed to additional connectors. The pushbutton interface might include an additional microcontroller, but could be implemented simply in logic.
- As drawn, the power supply is integrated on the interface board, with the same requirements as in the previous example. As stated there, optional voltage regulators for the analog circuitry are included on the microDXP for systems in which high-quality power supplies are not available.
- Again, some additional mechanical design, i.e. enclosure design, may be necessary.
Fig. 2: A system with a fully embedded host and user interface, with real time controls via the Auxiliary digital I/O.
Designing the system described above using conventional spectroscopy components would be a much more complex (and considerably more expensive) task, when compared with the solutions proposed here. Please contact the microDXP team at to discuss your application today!