The microDXP is a complete, low power compact digital spectroscopy card design for a wide range of handheld, benchtop and other embedded applications, lowering cost and speeding time-to-market. Its small size allows for very compact assemblies and its low power consumption assures thermal stability and extended battery life.

  • Compatible with almost any detector type, and Reset or RC preamplifiers
  • Output Count Rates approaching 1 Mcps per channel
  • Digital I/O lines for external instrument control and feedback.
  • USB-2.0 or RS-232 communication.
  • Low power (750 mW) for long battery life and thermal stability.
  • Credit-card size.
  • Operating parameters saved in non-volatile onboard memory.
  • Open source driver libraries for custom DAQ control
  • Development Kit board available for plug-and-ply power and communication and easy access to auxiliary I/O lines.




The microDXP hardware design was completely overhauled in 2015. Faster clock speeds, a new 14-bit ADC, improved analog design and more processing power have yielded dramatic improvements in energy resolution, peak stability and throughput. With these upgrades, the microDXP is now well-suited to work with the latest CUBE-based preamplifiers. In addition to x-ray spectroscopy with SDDs, PIN diodes or proportional counters, the microDXP is ideal for compact gamma spectroscopy systems using scintillators or CZT. For the highest resolution gamma spectroscopy systems with HPGe detectors, we recommend using the microDGF. microDXP applications include:

  • SDD, PIN diode, prop counter, scintillator, CZT and other detector types
  • Compact handheld and mobile x-ray and gamma-ray spectroscopy instruments.
  • Benchtop XRF machines
  • XRF conveyor belt metal sorting
  • Down-hole probes and other specialized tools. (Custom hardware configurations available)

More about Applications…


Technical Data

In common with all XIA digital pulse processors, the microDXP replaces the amplifier and MCA functions in conventional spectroscopy systems. The standard digitization rate is 40 MSPS, with an option for 80 MSPS for faster timing applications. The firmware for the FPGA and DSP is stored in a pre-loaded non-volatile flash memory. A PIC processor handles communications, boot-up, dedicated acquisition routines, and power management. In addition to serial I/O, auxiliary digital I/O are available to control external instrumentation, including the capability for I2C. XIA would be pleased to discuss developing custom DSP control code on an NRE basis.

The Development Kit includes the hardware and software necessary to get started with the microDXP, and provides a motherboard (the microCOMU) for filtered power, communication and easy access to I/O lines. All customers must purchase a development kit with their first microDXP order.


  • Credit-card sized unit replaces shaping amplifier, pileup inspector and multi-channel analyzer.
  • Very high throughput: Up to 1 Mcps output count rate with random pulses.
  • User settable gain and pileup inspection criteria.
  • Peaking times from 100 ns – 24 us (with standard 40 MSPS ADC).
  • High level integration of control and acquisition parameters into reconfigurable sets that are stored in non-volatile memory. Stored sets are accessible with a single command to easily switch between corresponding data acquisition modes.
  • Accurate ICR and live-time reporting for precise dead-time corrections.
  • Real multi-channel analysis, allowing for optimal use of data to separate fluorescence signal from backgrounds
  • High-Speed USB 2.0 or serial RS-232 communications
  • Alternate IDMA parallel interface supports a wide range of communications including Universal Serial Bus (USB).
  • Real-time control via 4 general purpose digital I/O lines, two of which can be configured for industry standard I2C interface.


Inputs Analog 10k Ohms input, +/-4.0 V range (no input attenuation*)
Designed to work with common reset or resistor feedback preamps of either polarity.*Other impedances and voltage ranges with on-board attenuation
Digital Gate (TTL 3.3V) signal used to suppress data acquisition
4 general purpose digital I/O lines for custom applications
Data I/O USB 2.0 On-board USB 2.0 is available
RS-232 RS-232 Serial communications up to 921 kBaud
OEM OEM Option 1: Analog Devices high-speed serial port (SPORT) via the flat-flex interconnect
OEM Option 2: 16-bit IDMA bus; 4 general purpose digital I/O lines, two of which can be configured for industry standard I2C interface; connected via a high-density board-to-board connector. The microComU USB interface employs this connection.
Real-Time I/O 4 general purpose digital I/O lines, two of which can be configured for industry standard I2C interface
Digitizer ADC 14-bits at 40 MSPS standard
high-speed 80 MSPS option
Digital Controls Gain Two gain options are available, combined with a digital fine gain adjustment ranging +/- 6dB
Gain Option 1 (standard): 25.5 dB range with 16 discrete computer-controlled gain settings
Gain Option 2: Fixed gain for embedded applications, lowest power consumption
Offset DC offset adjustment: -4.4V to +4.4V
(For RC-decay preamplifiers; assumes no input attenuation)
Shaping Three triangular/trapezoidall filters are employed to suppress noise, and to detect and acquire baseline and energy data:
Fast Filter: fully adjustable, from 50 ns to 6.4 us*
Intermediate Filter: tracks with Slow filter, from 50 ns to 6 us*
Slow Filter: 24 pre-selected peaking times from 100 ns to 24 us*, with adjustable gap/dwell time. *These numbers assume standard 40 MSPS ADC, and should be scaled for 80 MSPS option.
Thresholds A separate 12-bit (0-4095) threshold can be enabled/disabled and adjusted for each of the three filters
Pileup Two pileup rejection settings :
Fast filter time-over-threshold, aka maximum width constraint
Interval-between-events, aka peak interval constraint
Data collection MCA limits and number of bins
Dynamic Range
Data Outputs MCA 256 to 8192 channels (32 bits deep)
Additional memory for sum or 2D spectra
Statistics Livetime, runtime, input counts, output counts, overflows and underflows
Diagnostics Oscilloscope, baseline distribution, access to raw DSP memory
Hardware Power Requirements +/- 5V @ 50 mA clean supply, or +/-5.25V @ 50 mA dirty supply to feed on-board regulators
+3.3V @ 150 mA
Dimensions 2.125″ W x 3.375″ L

Examples of Systems that Incorporate the microDXP

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:

  1. Customized PIC microcontroller code is required to implement the I2C peripheral device control.
  2. Customized PIC microcontroller code is required to implement high-level data acquisition routines controlledthrough the user pushbutton interface.
  3. Customized DSP code is required for peak ratio calculations, possibly implemented in lookup tables.
  4. Minimal FiPPI (FPGA) code modification is required to implement the auxiliary digital I/O functionality.

User development required:

  1. 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.
  2. 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.
  3. 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!