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XIA microDXP, Technical Reference Manual

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microDXP Technical Reference Manual 

 

Version 3.15 

 

 

October 7, 2019 

 

21 

For general questions and DXP hardware issues please email 

[email protected]

  

1.7.5  Feedback 

XIA strives to keep up with the needs of our users. Please send us your feedback regarding 
the functionality and usability of the microDXP and ProSpect software. In particular, we 
are considering the following development issues: 

1.7.5.1 

Export File Formats 

We would like to directly support as many spectrum file formats as possible. If we do not 
yet support it, please send your specification to 

[email protected]

 

Summary of Contents for microDXP

Page 1: ...761 http www xia com Information furnished by XIA LLC is believed to be accurate and reliable However no responsibility is assumed by XIA for its use or for any infringements of patents or other right...

Page 2: ...11 1 2 2 Detector Preamplifier 11 1 2 3 Power Requirements 12 1 2 4 Operating Environment 12 1 2 5 Regulatory Compliance 12 1 3 Hardware Options 12 1 3 1 Communications and Power Interface 12 1 3 2 A...

Page 3: ...ings 22 2 1 1 Preamplifier Type Selection 22 2 1 2 Input Signal Attenuation 22 2 2 Board State and Configuration 23 2 2 1 Board Information and Status 23 2 2 1 1 ADC Sampling Rate DSP Clock Speed DSPS...

Page 4: ...meter Set 30 2 6 2 Download a Master Parameter Set 30 2 7 Data Acquisition 30 2 7 1 Starting a Run 31 2 7 2 Stopping a Run 31 2 7 3 Reading a Spectrum 31 2 7 4 Reading and Calculating the Run Statisti...

Page 5: ...Parallel Flash EEPROM 44 3 5 2 Serial Port SPORT 44 3 5 3 DMA Port 44 3 5 4 DSP Code Variants 44 3 6 PIC Microcontroller 44 3 6 1 RS 232 Serial Port 45 3 6 2 I2C Serial Bus 45 3 6 3 I2C EEPROM 45 3 6...

Page 6: ...ng 57 4 7 Pile up Inspection 58 4 7 1 Slow Pileup 59 4 7 2 Fast Pileup 60 4 8 Input Count Rate ICR and Output Count Rate OCR 61 4 9 Throughput 61 Appendices 63 Appendix A MicroDXP Hardware Specificati...

Page 7: ...er supply in the 100VAC to 240VAC range at 50Hz or 60Hz Use of this development kit with AC voltage outside these specifications could damage the unit and nullify the product warranty Refer to Chapter...

Page 8: ...bligated to furnish service under this warranty a to repair damage resulting from attempts by personnel other than XIA LLC representatives to repair or service the product or b to repair damage result...

Page 9: ...ard sections of code file contents and syntax examples Setup exe refers to a file called setup exe on the host computer Italics Italic text denotes a new term being introduced or simply emphasis peaki...

Page 10: ...ports custom auxiliary digital access including the industry standard I2C serial bus and four configurable digital I O lines The microDXP is thus a flexible cost effective OEM component that can form...

Page 11: ...ry XIA provides the ProSpect software application for microDXP parameter set configuration intended for use both in evaluation and production phases 1 1 3 Custom OEM Features Customized firmware devel...

Page 12: ...modest gamma or X ray flux above a certain level this radiation will start to cause bit errors in the digital components If necessary please contact XIA LLC to discuss a proposed radiation environment...

Page 13: ...pplied directly either linear regulated or high quality switching supplies should be used If the on board LDO regulators are used a minimum of 5 50 V is required and the ripple requirement can be rela...

Page 14: ...t the one percent level and only digital scaling is used for energy calibration The fixed gain option offers better performance in some cases and somewhat lower power consumption The analog gain is fu...

Page 15: ...instrument s flexibility 1 5 1 Example 1 General Purpose USB Spectrometer with MicroComU Companion Board In this example the microDXP microComU board set acts as a general purpose spectrometer connect...

Page 16: ...nal mechanical design i e enclosure design may be necessary The microDXP power supplies and routing adapter together constitute a spectrometer that can be connected to virtually any controller with RS...

Page 17: ...e control 2 Customized PIC microcontroller code is required to implement high level data acquisition routines controlled through the user pushbutton interface 3 Customized DSP code is required for pea...

Page 18: ...resides in the hardware and executes the command set 1 6 1 User Interface e g ProSpect The host software communicates with and directs the microDXP via a driver layer and displays and analyzes data a...

Page 19: ...e firmware combination since most problems are actually solved at the software level Please check for the most up to date standard versions of the microDXP software and firmware at http www xia com mi...

Page 20: ...conflict among themselves This can cause the DXP unit to report data that apparently make no sense such as bad peak resolution or even empty spectra Each time a problem is reported to us we diagnose i...

Page 21: ...th the needs of our users Please send us your feedback regarding the functionality and usability of the microDXP and ProSpect software In particular we are considering the following development issues...

Page 22: ...detector preamplifier for the first time 2 1 1 Preamplifier Type Selection The preamplifier type selector switch if present should already be set properly Note that the setting must agree with the fi...

Page 23: ...d versions Select the Status tab to display information about the current state of the PIC DSP and data acquisition run The RS 232 command to read board information is 0x49 Please refer to the RS 232...

Page 24: ...cessed via the Detector and Advanced tabs of the Settings panel Because these settings are global changes are simultaneously applied and saved to nonvolatile memory via the Apply Save button 2 3 1 Pre...

Page 25: ...ing the delay longer than necessary introduces additional processor dead time which will reduce the data throughput at high count rates In ProSpect RESETINT is set via the Reset Interval field in the...

Page 26: ...o define a spectrum that exceeds the practical limits of the ADC which should be avoided As a rule of thumb the product of Number MCA Bins and MCA Bin Width should not exceed 8192 If the product is la...

Page 27: ...ched Gain and Digital Base Gain Please first review 3 2 2 for a description of the updated analog gain circuitry and digital gain coefficient and 2 2 1 2 to determine if the Switched Gain feature is i...

Page 28: ...ven combination more than once The factory set default spectrometer settings should be adequate to acquire a recognizable spectrum To achieve optimal performance the spectrometer settings must be adju...

Page 29: ...ging In ProSpect Baseline Average Length is accessed in the Acquisition tab of the Settings panel Select the desired multiple of 2 value from the drop down list Modifications for the selected PARSET c...

Page 30: ...RS 232 command to save the current PARSET table is 0x8D Please refer to the RS 232 Command Specification for details 2 6 Repetitive Configuration of Identical Systems In cases where many microDXP card...

Page 31: ...e entire spectrum Each MCA bin is represented in DSP program memory as a 24 bit word i e 3 bytes supporting up to 16 777 215 counts per bin In some cases i e for short runs and or low count rates the...

Page 32: ...ely to units of 500 nanoseconds the process that monitors the real time and live time is only updated every 500 microseconds Similarly the input and output counts are tallied every 500 microseconds Th...

Page 33: ...ntermediate Filter 3 The output of the intermediate baseline filter before baseline subtraction Baseline Samples 4 Samples of the raw intermediate filter when at baseline Baseline Average 5 A running...

Page 34: ...on zero is crossed Intermediate Slow Trigger 2 A trigger is generated whenever the intermediate filter Baseline threshold if non zero or slow filter Energy threshold if non zero is crossed MCA Event 3...

Page 35: ...command to read the baseline histogram is 0x10 The RS 232 command to read the baseline history is 0x12 Please refer to the RS 232 Command Specification for details 2 8 3 DSP Parameters The instantaneo...

Page 36: ...memory The functions of each block are summarized below This chapter does assume the reader has some familiarity with x ray pulse processing theory and electronic devices Please see Chapter 4 of this...

Page 37: ...ier output signal such that a moderately priced ADC can be used 3 2 1 1 Reset Type Preamplifiers For reset type preamplifiers the dynamic range reduction is accomplished using a novel technology for w...

Page 38: ...h then remedies the situation by quickly closing the reset switch During this so called Tracking Step data passed to the FiPPI are invalid Preamplifier resets are detected similarly Note Data acquisit...

Page 39: ...devices introduce excessive noise temperature drift and significant non linearities into the signal In a significant departure from the previous design the updated blue microDXP design now employs a d...

Page 40: ...in The Nominal Gain is independent of software control Its value is stored in non volatile memory accessible via the DSP parameters NOMGAIN UQ1 15 format unsigned mantissa and NOMGAINE exponent It is...

Page 41: ...digitizes at either 40 MSPS default or 80 MSPS high speed option The ADC itself and passive components in the Nyquist filter are different in each case thus the clock speed cannot be increased via fir...

Page 42: ...the previous design the microDXP now employs a switched gain amplifier architecture to offer up to 16 discrete analog gain settings i e gain that is applied to the analog signal before digitization S...

Page 43: ...gy calibration is slightly off To first order the spectrum should remain calibrated but a slight shift in the pulse height measurement is not uncommon This is addressed by storing a unique Fine Gain T...

Page 44: ...5 2 Serial Port SPORT The Analog Devices DSP synchronous serial port or SPORT supports a variety of serial data communications protocols and offers a maximum transfer rate of approximately 1Mbyte sec...

Page 45: ...f other devices 3 6 3 I2C EEPROM The I2C serial EEPROM accessed by the PIC is used to store the DSP code and general system information The DSP is booted automatically upon power up The I2C memory can...

Page 46: ...d on the microDXP The so called high speed interface includes all resources carried on the flex cable interface plus Direct Memory Access DMA to the DSP It was included for applications requiring very...

Page 47: ...e requires a measurement of the voltage step Vx in the presence of the amplifier s noise Figure 4 1 and Figure 4 3 depict reset type and RC type charge sensitive amplifiers respectively In both figure...

Page 48: ...rom successive x ray steps followed by the reset Note that the units here are Volts and milliseconds vs millivolts and microseconds in the previous figure Figure 4 2 The large signal reset waveform fo...

Page 49: ...y applicable to RC type preamplifiers Figure 4 3 a RC type charge sensitive preamplifier with a positively biased detector b Output on absorption of an x ray Note that the step has a falling edge thus...

Page 50: ...tep then the equation produces cusp like filters When the weighting values are constant one obtains triangular if the gap is zero or trapezoidal filters The concept behind cusp like filters is that si...

Page 51: ...cally that if the noise in the signal is white i e Gaussian distributed above and below the step which is typically the case for the short shaping times used for high signal rate processing then the a...

Page 52: ...s offering both triangular and semi Gaussian filtering by stretching the triangular peaking time a bit so that the true triangular peaking time is typically 1 2 times the selected semi Gaussian peakin...

Page 53: ...tion e which is referred to as the electronic noise of the system a number which depends on the peaking time of the filter used Riding on top of this noise the x ray peaks contribute an additional noi...

Page 54: ...the energy filter itself or a derivative of it is sampled periodically in the explicit absence of an x ray step defined by a baseline threshold In practice the DXP initially makes a series of NB base...

Page 55: ...resolution at high rates The microDXP now employs a proprietary circuit that virtually eliminates this problem resulting in industry leading count rate stability 4 5 X ray Detection Setting Thresholds...

Page 56: ...is usually trivial digitally then no system deadtime is produced by the capture and store operation This is a significant source of the enhanced throughput found in digital systems Once an active thre...

Page 57: ...il in 4 7 Figure 4 7 In the default Peak Sensing mode the slow filter output is monitored and the peak value is selected This automatic mode typically yields the best performance In Peak Sampling mode...

Page 58: ...LEN SLOWGAP X Equation 4 9 4 7 Pile up Inspection The captured value Vx see Figure 4 6 will only be a valid measure of its associated x ray s energy provided that the filtered pulse is sufficiently we...

Page 59: ...ritically on the peaking time of the filter being used The amount of pileup which occurs at a given average signal rate will increase with longer peaking times We will quantify this in 4 9 where we di...

Page 60: ...only a single though somewhat distorted pulse emerges from the slow filter but its peak amplitude corresponds to the energy of neither x ray 4 nor x ray 5 In order to reject as many of these fast chan...

Page 61: ...as the OCR The DXP normally returns statistics in addition to the collected spectrum the REALTIME for which data was collected the triggering channel LIVETIME or sum of time during which the triggeri...

Page 62: ...racking steps both of which incur additional dead time d 2 Peaking Time Gap Time Equation 4 15 The maximum value of OCR can be found by differentiating Equation 4 14 and setting the result to zero Thi...

Page 63: ...microDXP excluding reset transients that may exceed the range for a few microseconds The input range is specified below in Table A 1 To accommodate preamplifiers with an output range in excess of 4V V...

Page 64: ...nications as well as parallel IDMA access to DSP memory for transfer rates up to 10 Mbytes sec This parallel IDMA interface is used as the basis for the microCOMU USB interface The latest microDXP har...

Page 65: ...nput connection J12 Flex Cable Port 30 conductor 0 5mm locking flex cable connector carries power communications and auxiliary digital I O Hirose P N FH12 30S 0 5SH e g flat flex cable Parlex P N 0 5M...

Page 66: ...al port receive frame sync line ADSP218x SPORT Table A 5 Pin assignments for the 30 conductor flat flex interconnect J11 Board to Board Port 50 conductor 0 5mm mezzanine board to board receptacle carr...

Page 67: ...signal conditioner Regulated 5 0V or unregulated 5 5V if on board regulator present 6 3 3VCC 3 3V DC supply for on board digital components 8 GND Internal ground connection 10 SPORT_RFS DSP serial por...

Page 68: ...100mV pk pk from the switching supplies Voltage Range Current max Description 3 3V 150mV 200mA Decent switching supply 5 5V to 6 0V 30mA Linear or good switching supply 5 5V to 6 0V 30mA Linear or goo...

Page 69: ...42 3 for details ID Parameter Description 0 NUMGENSET Number of GENSET parameters NOT including NUMGENSET and GENVERSION used internally 1 GENVERSION Version of the GENSET used internally 2 MCALEN Nu...

Page 70: ...ternally 2 FASTLEN Fast filter ramp length 3 FASTGAP Fast filter gap 4 FSCALE Controls FiPPI fast filter scaling 5 MINWIDTH Minimum time above threshold for fast filter 6 MAXWIDTH Maximum time above t...

Page 71: ...data bytes xor CS Exclusive or checksum bitwise xor of all bytes except for the initial Esc If the checksum is not correct an error response is returned Table E 1 RS 232 character definitions The for...

Page 72: ...byte of the new RUNID 0x1B 27 0x18 bitwise XOR excludes escape character Response if unsuccessful 0x1B the escape character 0x00 the command is always returned 0x01 the low byte that sets the number...

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