One of the proposed solutions for upgrading the high voltage (HV) system of Tilecal, the ATLAS hadron calorimeter, consists in removing the HV regulation boards from the detector and deploying them in a low-radiation room where there is permanent access for maintenance. This option requires many ~100 m long HV cables but removes the requirement of radiation hard boards. That solution simplifies the control system of the HV regulation cards (called HVRemote). It consists of a Detector Control System (DCS) node linked to 256 HVRemote boards through a tree of Ethernet connections. Each HVRemote includes a smart Ethernet transceiver for converting data and commands from the DCS into serial peripheral interface (SPI) signals routed to SPI-capable devices in the HVRemote. The DCS connection to the transceiver and the control of some SPI-capable devices via Ethernet has been tested successfully. A test board (HVRemote-ctrl) with the interfacing sub-system of the HVRemote was fabricated. It is being tested through SPI-interfaces and several devices were already validated. A next version adds a few more ADC/DAC devices for checking their suitability for the final design.Peer Reviewe

Evans, Guiomar

Gomes, Agostinho

Gurriana, Luis

Maio, Amelia

Martins, Filipe

Rato, Catia

Sabino, Joao

Seabra, Luis

Soares Augusto, Jose

English

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CONTROL SYSTEM FOR ATLAS TileCal HVRemote BOARDSF. Martins∗, L. Gurriana, L. Seabra, LIP, PortugalG. Evans1, A. Gomes2, A. Maio2, C. Rato, J. Sabino, J. Soares Augusto3Faculdade de Ciências da Universidade de Lisboa, Portugal1also at BioISI, Universidade de Lisboa, Portugal2also at LIP, Portugal3also at Inesc-ID, PortugalAbstractFor the high luminosity LHC one of the proposed solu-tions for upgrading the high voltage (HV) system of theATLAS central hadron calorimeter (TileCal), consists inremoving the HV regulation boards from the detector anddeploying them in a low-radiation room where there is per-manent access for maintenance. This option requires many∼100 m long HV cables but removes the requirement ofradiation hard boards.This solution simplifies the control system of the HV reg-ulation cards (called HVRemote). It consists of a DetectorControl System (DCS) node linked to 256 HVRemote boardsthrough a tree of Ethernet connections. Each HVRemoteincludes a smart Ethernet transceiver for converting dataand commands from the DCS into serial peripheral interface(SPI) signals routed to SPI-capable devices in the HVRe-mote. The DCS connection to the transceiver and the controlof some SPI-capable devices via Ethernet has been testedsuccessfully.A test board (HVRemote-Ctrl) with the interfacing sub-system of the HVRemote was fabricated. It is being testedthrough SPI-interfaces and several devices were already val-idated. A next version adds a few more ADC/DAC devicesfor checking their suitability for the final design.INTRODUCTIONThe Tile Calorimeter (TileCal) [1] is the central hadroniccalorimeter of ATLAS [2], one of the two multi-purposeexperiments at the Large Hadron Collider (LHC) at CERN.The high luminosity LHC (HL-LHC) aims to deliver a lu-minosity increased by a factor of 5 to 10 compared to theLHC design value [3]. The HL-LHC environment presentsseveral challenges for TileCal and an upgrade program isbeing prepared for the detector. TileCal uses iron plates asabsorber and plastic scintillating tiles as the active material.Light produced in the scintillators is transmitted by wave-length shifting fibres to photomultiplier tubes (PMTs). Anelectronic system currently being upgraded is that in chargeof the control and distribution of high-voltage (HV) to theapproximately 104 PMTs of the TileCal detector. In the cur-rent operational version, its core comprises two cards [4]:the HVOpto and the HVMicro. In the current ATLAS setup,this system is located inside the detector, so it operates underhigh doses of radiation. Current TileCal HV electronics is∗ fmartins@lip.ptin operation for more than 10 years and, as a result, is ageingdespite its design accounted for radiation hardness. Anothersevere constraint is the difficulty in maintaining and replac-ing faulty HVOpto or HVMicro cards: it is never possible toreplace them when the LHC is running, and the maintenanceis possible only during the yearly winter shutdowns.To alleviate these constraints, the solution proposed forthe upgrade [5, 6] moves the TileCal’s HVOpto electroniccontrol system from the detector innards, to a location in theUSA15 room which is a low radiation environment far away(100 m) from the detector. This will improve the lifetimeof the system and provides for immediate maintenance andreplacement. On the other hand, the HVRemote1 board willnow be connected to the PMTs through several 100 m longcables, which may worsen slightly their stability and noiselevels. Since the current electronic design is about 20 yearsold, some components in the HVOpto, such as the ADCsand DACs2, are obsolete and have to be replaced by modernalternatives.In addition, an HV system was developed by Argonne Na-tional Laboratory team, which keeps the HV regulation anddistribution electronics in the detector [7], and is a possiblealternative solution for the upgrade.In this note we describe the ongoing work regarding theupgrade of the control system of the HV cards for the HVRe-mote version. Most of the tests presented here, which aim atevaluating and validating several design options, were basedin prototype boards, called HVRemote-Ctrl cards, whichcontain downsized replicas of the hardware of the commu-nications interface of the full HVRemote board. One of theHVRemote-Ctrl cards is described below.THE HVRemote CONTROL SYSTEMThe HVRemote Control Path and HardwareThe architecture of the upgraded electronics system ofthe TileCal is shown in Fig. 1. The control master is aPC/workstation configured as a node of the DCS of ATLAS.The DCS commands sent to, and the data read from theHVRemote boards, flow through a tree of Ethernet links,connecting the PC and 256 boards, each of these managing48 PMT channels.1 The "old" HV system, now in operation is referred to as HVOpto and theupgraded system is referred to as HVRemote.2 DAC refers to a generic Digital-Analogue Converter; ADC refers to ageneric Analogue-Digital Converter.16th Int. Conf. on Accelerator and Large Experimental Control Systems ICALEPCS2017, Barcelona, Spain JACoW PublishingISBN: 978-3-95450-193-9 doi:10.18429/JACoW-ICALEPCS2017-THPHA069Hardware TechnologyTHPHA0691543ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2017).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.The control software consists of DCS (high-level com-mands), C++ and Python programs, running in the PC, whichuse the DCS API (Application Programming Interface), andalso C programs running in the Tibbo EM1206 modules (de-scribed below). Each HVRemote board includes one TibboEM1206 module which is used to read commands from theEthernet channel, convert them into raw digital signals andsend them to HVRemote’s digital control circuits througha SPI link. The Tibbo EM1206 modules also manage thereverse data flow (from the HVRemote to the upstream DCScomputers.)Figure 1: Architecture of the HVRemote control tree.The HVRemote-Ctrl Testing CardTo evaluate the supervising and control system of theHVRemote before this complex and costly board is fullyassembled, a test card was built, called HVRemote-Ctrl (Figs.2 and 3), which has the same control/interfacing componentsof the HVRemote, but misses the front-end electronics ofthe 48 PMTs. This allows the testing of both the digitalcontrol hardware and the Tibbo module, and the assessmentof the transfer speeds. The HVRemote-Ctrl has already beenassembled and tested. The DAC and ADC in this card areplatforms for evaluating test algorithms to be applied to theHVRemote board in the future.The hardware of theHVRemote-Ctrl card ADC leveltranslator MAX3002 provides compatibility for the 3.3 Vand 5 V signals shared by the Tibbo module and the CMOShardware. The HVRemote-Ctrl card has a 16-bit port ex-pander with SPI interface (MCP23S17), a 12-bit DAC(DAC7568), a 16-bit analogue multiplexer (MPC506), an in-strumentation amplifier (INA128), a 12-bit ADC (TLV2541),a temperature sensor (TMP17) and a voltage reference(AD589).These are the same components (but in less quantity), andinterfacing architecture, found in the HVRemote full cardundergoing fabrication at present. The HVRemote-Ctrl cardalso allows applying the histogram test to each individualdata converter using several digital pseudorandom uniformnoise generators (UNGs). In some of the current test settingsused with the card, an Arduino replaces the commercial mod-ule EM1206+RJ203 (shown in the centre of Fig. 2) in therole of SPI master and so the DC/DC converter MAX3002is not needed and is tested separately.To access and control the electronic components in theHVRemote-Ctrl card, the serial data from the SPI is con-verted to a parallel format. This is required due to thepin-count constraints of the Tibbo module. That serial-to-parallel conversion occurs in the MCP23S17 expander: thedata in parallel configures the DAC, ADC and multiplexer’sparameters (Fig. 4). The MCP23S17 has 16 general pur-pose input/output pins (two byte-wide ports, GPA and GPB)backed and configured by several internal registers. Thesignals relayed by the expander link the Tibbo module tothe functional devices. There are four lines dedicated to theSPI protocol (CS, SCK, SI and SO) which interface with theTibbo module.Software for testing the HVRemote-Ctrl card A userinterface written in Python was developed to test the board’scomponents. The test of the expander has already been com-pleted with success. In the user interface window for testingthe expander, the user sends 16 bits as two-byte strings (cor-responding to the two ports, GPA and GPB) and the datawritten in the ports will be sent back, received by the ArduinoUno and saved in a file.The communication with the expander is done throughthe Arduino IDE. Since the user interface is developed inPython and runs in the PC, a logical serial communicationchannel is established between the Arduino and the Pythonuser interface, such that this interface can send/receive thedata to/from the expander which is in the HVRemote-Ctrlcard.In the user interface, the received data is assembled in anarray, processed and saved to a file. All the read/write testsalready done ended with success, and so it was concludedthat it is safe to use the expander to configure and test theother components in the HVRemote-Ctrl card.Testing of converters with pseudorandom noise gen-erators and histogram tests The components in theHVRemote-Ctrl card have already been fully tested. Thestatic characterization of both DACs and ADCs was donewith histogram tests, performed with two digital pseudoran-dom uniform noise generators (NGs): the Mersenne-Twisteralgorithm for the uniform NG [8] and the Box-Muller algo-rithm for the Gaussian NG [9]. The technique has proven tobe a powerful method to characterize converters [10, 11].16th Int. Conf. on Accelerator and Large Experimental Control Systems ICALEPCS2017, Barcelona, Spain JACoW PublishingISBN: 978-3-95450-193-9 doi:10.18429/JACoW-ICALEPCS2017-THPHA069THPHA0691544ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2017).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.Hardware TechnologyFigure 2: Protocols in the HVRemote monitoring, supervising and control system. The first HVRemote-Ctrl prototype isshown.Figure 3: Simplified block diagram of the HVRemote-Ctrl card. Not all signals are shown.Figure 4: MCP23S17 signals in the HVRemote-Ctrl card.In the first step, the offset voltage and gain error of theconverter are obtained. After the correction of these errors,the differential (DNL) and integral (INL) non-linearities arecalculated. The evaluation of the static errors profile of theADCs and DACs is important to the calibration of the HVlevels applied to the PMTs.The user interfaces for orderly applying these tests andcharacterizing the converters are finished and the test algo-rithms are fully operational and have already been used.Evaluation of the Tibbo EM1206+RJ203 Moduleand Connection with the DCS SystemAlong with the testing of the hardware used in the inter-face of the HVRemote card, the digital communication linkbetween the DCS system and the HVRemote interface havebeen fully tested. This means that the Ethernet link betweenthe DCS and the Tibbo module, as well as the operation ofthis module acting as a SPI Master device, have been tested.This task comprises the two channels and protocols shownin Fig. 2. The important systems in this test task are theTibbo module EM12016+RJ203 (or the evaluation board),the DCS software and the MCP23S17 expander.Testing Ethernet communication with the Tibbo mod-ule In preliminary tests aiming to probe the Ethernet in-terfacing solution, a Tibbo EM1206-EV evaluation boardwas used and, in more recent tests, the Tibbo moduleEM12016+RJ203 itself (see Fig. 2). One of these moduleswill be soldered to each HVRemote. Tibbo supplies an inte-16th Int. Conf. on Accelerator and Large Experimental Control Systems ICALEPCS2017, Barcelona, Spain JACoW PublishingISBN: 978-3-95450-193-9 doi:10.18429/JACoW-ICALEPCS2017-THPHA069Hardware TechnologyTHPHA0691545ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2017).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.grated development system for the board, which includes Clibraries for sockets programming and SSH communications,two important libraries for our work. Tibbo also supplies astandalone tool, the IO Ninja, which allows testing the Eth-ernet communication channel between the Tibbo module, orevaluation board, and the PC.The Tibbo module is programmed either in C or in BASIC.A raw Ethernet client using sockets was developed in C anddeployed in the module. It succeeded in communicatingwith an Ethernet master in the PC, programmed in Python,and also worked flawlessly as an Ethernet/sockets masterwhen using the IO Ninja.Interfacing DCS with HVRemote-Ctrl The DCS sys-tem was installed and runs with full functionality in a work-station in our laboratory. This platform was used to performcommunication tests. The main goal was to exercise thehand-shaking between DCS and the Tibbo Ethernet hard-ware.A DCS user interface which sends/receives commandsand data to/from the Tibbo module has been developed.These commands are applied to external hardware – theMCP23S17 expander –, a process that simulates the accessto the HVRemote interface through an SPI channel. In Fig.5 it is shown a small part of a DCS control panel preparedto drive each channel of the HVRemote board, which wasdeveloped using a supervision, control and data acquisitionsystem, the WinCC Open Architecture, belonging to theSCADA SIMATIC development system [12].Before the HVRemote-Ctrl board was fabricated, thesetests were performed in a setup where the Tibbo modulecommunicated with a MCP23S17 expander mounted in abreadboard (Fig. 6).Figure 5: Partial view of the WinCC DCS interface devel-oped for the HVRemote card.Figure 6: Tibbo evaluation card communicating with anMCP23S17 through an SPI channel. The Tibbo evaluationcard is driven by DCS commands coming from the worksta-tion.The Tibbo module and the SPI interface The perfor-mance of the SPI interface in the Tibbo module was testedin several setups. For instance, SPI connection with twodevices in a same SPI bus was established using two Ar-duino boards as SPI slaves, because the module will haveto manage three MCP23S17 port expanders when linked tothe full HVRemote card. In Fig. 7 it is shown a test signalwhere the SPI clock in the Tibbo was set to a frequency of200 kHz.Figure 7: SPI signal (MOSI or SI) during communication.The transmission clock in the Tibbo was set to a periodof about 5 μs (2 periods per oscilloscope division in thisimage).RESULTS AND CONCLUSIONThe development of the HVRemote was driven by knowl-edge gained from evaluating the HVRemote-Ctrl card. Thefollowing tasks have been completed:• Development and assembly of the HVRemote-Ctrl card,to evaluate the digital control and supervising system.This prototype card is already partially tested (Fig. 2).• Development, in Python, of a panel to manage theHVRemote-Ctrl cards.16th Int. Conf. on Accelerator and Large Experimental Control Systems ICALEPCS2017, Barcelona, Spain JACoW PublishingISBN: 978-3-95450-193-9 doi:10.18429/JACoW-ICALEPCS2017-THPHA069THPHA0691546ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2017).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.Hardware Technology• Evaluation of the Tibbo EMS1206 module as a suitableEthernet controller for the HVRemote board.• Evaluation of the Tibbo EMS1206 module as SPI mas-ter, using multiple microcontrollers (Arduinos) config-ured as SPI slaves.• Development of a DCS control panel, underlying func-tions, and establishment of Ethernet communicationsbetween DCS and the Tibbo module (Fig. 5).The speeds measured in both Ethernet and SPI communica-tions with the Tibbo module are suitable to monitor in realtime all the 256 HVRemote boards and ∼104 PMTs in theTileCal (each PMT is monitored every few seconds). Theassembly of a prototype of a full HVRemote card is almostfinished and the software already developed will be adaptedand scaled to target that board instead of the HVRemote-Ctrltest board.ACKNOWLEDGEMENTSThis work is funded in part by the "Fundação para a Ciên-cia e a Tecnologia", Portugal, under the project "Colaboraçãona Experiência ATLAS", CERN/FIS-NUC/0005/2015.REFERENCES[1] ATLAS TileCal Collaboration, "Tile Calorimeter TechnicalDesign Report", ATLAS Internal Note, CERN/LHCC/96-42(1996).[2] ATLAS Collaboration, "The ATLAS Experiment at theCERN Large Hadron Collider", 2008 JINST 3 S08003.[3] ATLAS Collaboration, "ATLAS Phase-II Upgrade ScopingDocument", CERN-LHCC-2015-020, (2015).[4] R. Chadelas et al., "High voltage distributor system forthe Tile hadron calorimeter of the ATLAS detector",ATLAS-TILECAL-2000-003, 2000, https://cds.cern.ch/record/436230[5] F. Vazeille, "Performance of a remote High Voltage powersupply for the Phase II upgrade of the ATLAS Tile Calorime-ter", JINST 11 C02050, 2016.[6] A. Gomes, "The new front-end electronics for the ATLASTile Calorimeter Phase 2 Upgrade", JINST 11 C02015, 2016.[7] G. Drake, "The New Front-End Electronics forthe ATLAS Tile Calorimeter Phase 2 Upgrade",ATLAS note ATL-TILECAL-PROC-2015-023,https://cds.cern.ch/record/2114792[8] M. Matsumoto, and, T. Nishimura, "Mersenne Twister: A623-Dimensionally Equidistributed Uniform PseudorandomNumber Generator", ACM Transactions on Modeling andComputer Simulation, vol.8, no. 1, pp.3–30, 1998.[9] D.-U. Lee, J. D. Villasenor, W. Luk and P. H. W. Leong, "AHardware Gaussian Noise Generator Using the Box-MullerMethods and Its Error Analysis", IEEE Transactions on Com-puters, vol. 55, no. 6, pp. 659-671, June 2006.[10] J. Alves and G. Evans, "Digital Pseudorandom UniformNoise Generator for ADC Histogram Test", DCIS 2015– XXX Conference on Design of Circuits and IntegratedSystems, pp. 1- 6, Estoril, Portugal, November 2015,DOI: 10.1109/DCIS.2015.7388592.[11] J. D. Alves and G. Evans, "A Digital Pseudorandom UniformNoise Generator for ADC Built-In Self-Test", 2015 10thIEEE International Conference on Design & Technologyof Integrated Systems in Nanoscale Era (DTIS), pp. 1-5,Naples, Italy, April 2015.[12] http://w3.siemens.com/mcms/human-machine-interface/en/visualization-software/scada/pages/default.aspx, https://en.wikipedia.org/wiki/WinCC, (Siemens, SIMANTEC SCADA system),January 2017.16th Int. Conf. on Accelerator and Large Experimental Control Systems ICALEPCS2017, Barcelona, Spain JACoW PublishingISBN: 978-3-95450-193-9 doi:10.18429/JACoW-ICALEPCS2017-THPHA069Hardware TechnologyTHPHA0691547ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2017).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.

Control system for ATLAS TileCal HVRemote boards

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Control system for ATLAS TileCal HVRemote boards

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