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50AN EMBEDDED SINGLE CHIPTEMPERATURECONTROLLER DESIGNJ. Jayapandian and Usha Rani RaviDesign Development & Services Section, Materials Science DivisionIndira Gandhi Centre for Atomic Research, Kalpakkam 603 102. Tamil Nadu. IndiaABSTRACTThis paper describes a single chip embedded temperature controller design programmedin a single Programmable System on Chip (PSoC); a mixed array logic consists of analog,digital and digital communication blocks within in it. The virtual instrument controlprogram written in LabVIEW ver.7.1, a graphical language, provides user friendly menudriven window based control panel, interacts with the single PSoC chip design for sensingand controlling the temperature. This simple cost effective embedded design findspotential application in laboratory as well as in industries. This deign can also be madeas a standalone system without PC by programming LED/ LCD display and key padattachment modules in same PSoC chip.1. INTRODUCTIONThe advent of intelligent programmable embedded silicon designs provides the ability toimplement any required hardware programmatically for the design automation in industriesand laboratories. Recent trend in laboratory as well as in industrial automation designs usesminimal hardware and maximum support of software. The programmable embeddedcomponents and application software available in the market enables the designer for userfriendlycost effective design solution for any system automation. Temperature controllersare playing vital role in industries and laboratories. To accurately control process temperaturewithout extensive operator involvement, a temperature control system relies upon a controller,which accepts a temperature sensor such as a thermocouple or RTD as input. It comparesthe actual temperature to the desired control temperature, or set point, and provides an outputto a control element. The controller is one of the major parts of the entire control system,and the whole system should be analyzed in selecting the proper controller. This paperdescribes a novel single chip temperature controller design with Cypress MicrosystemsProgrammable System on Chip (PSoC). Virtual instrument control program written in LabVIEWver.7.1 interacts with the embedded PSoC design and senses and controls the temperature offurnace / load.J. Instrum. Soc. India 38(1) 50-54512. PROGRAMMABLE SYSTEM ON CHIP (PSoC)While selecting a microcontroller, it must have an easy and inexpensive interface tosensors, communication interfaces, and more. Cypress Programmable System-On-Chip (PSoC)architecture offers a flexible, economical solution for a wide variety of applications. This paperdescribes the design of a temperature controller on a single CY8C27143, 8 pin PSoC chip. Asshown in fig.1, it features four main areas: PSoC core, digital system, analog system, andsystem resources including in/out ports. This architecture allows the user to create customizedperipheral configurations that match the requirements of each individual application. The UARTinterface, coupled with configurable analog and digital peripherals makes the CY8C27143 trulyuniversal in its connections to the external world. The PSoC core includes: an M8Cmicrocontroller; 32 Kbytes of program flash memory; 2 Kbyte of data RAM; internal 24 MHzoscillator; sleep and watchdog timer; general-purpose input/ output pins (GPIO) allowing anypin to be used as digital input or output, and most pins to be used as analog inputs or outputs.Every pin can be used as a digital or analog interrupt. The digital system is made up of 8digital PSoC blocks. Each block is an 8-bit resource that can be used alone or combined withother blocks to form peripherals. Possible peripherals include: PWMs (8- to 32-bit); PWMswith dead band (8- to 24-bit); counters (8- to 32-bit); UART 8-bit with selectable parity; SPImaster and slave; cyclical redundancy checker/generator (8- to 32-bit); pseudo randomsequence generators (8- to 32-bit). These digital blocks can be connected to any of the GPIOthrough a series of global buses. These buses also allow for signal multiplexing and performinglogic operations. The analog system is made up of 12 configurable blocks, each comprisingan op amp circuit allowing the creation of complex analog signal flows. Analog peripheralsFig. 1 : Block diagram of Programmable System on Chip (PSoC) internal blocksAn embedded single chip temperature controller design52are very flexible and can be customized to support specific application requirements. Someof the more common PSoC analog functions are: filters (2- and 4- pole band-pass, low-pass,and notch); amplifiers (up to 2, with selectable gain to 48x); instrumentation amplifiers (1with selectable gain to 93x); comparators (up to 2, with 16 selectable thresholds); DACs (upto 2, with 6- to 10-bit resolution); and SAR ADCs (up to two, with 6-bit resolution). Incombination with the digital blocks, additional functions can be created, including: incrementalADCs (up to 2, with 6- to 14-bit resolution); delta sigma ADC (1,with 8-bit resolution at62.5ksps). The additional system resources provide additional capability useful for the completesystem design.3. VIRTUAL INSTRUMENT PROGRAMVirtual instrument (VI) is an application of general purpose digital PCs for the measurementand control of various physical variables. The VI program mimics the control processes, whichare in a remote area, on the PC screen. On-going process control automation can be visualizedby the experimentalist through PC screen. VI program provides inexpensive and yet a powerfulplatform for the control and data acquisition of process variables. These programs are easyto implement with graphic languages (G-language). The “G” language implements the dataflow technique. The usage of “G” language VIs provides easy interfacing with PCs under theWindows environment 2. The “G” language provides built-in function libraries for a varietyof application requirements as graphic palettes, which in turn supports the required DLLs forthe functions to run under windows environment. Usually the “G” language VI programs consistof two frames viz., panel diagram and functional diagram. In the panel diagram,programmers can assign various controls and indicators (i.e., input and output variables) asper their requirements and in the functional diagram, the designers can implement the requiredJ. Jayapandian and Usha Rani RaviFig. 2 : PSoC designer screen for single chip temperature controller53functions available as a function library in LabVIEW. National Instruments LabVIEW version7.1 incorporates all the necessary functions as icons in its package.4. PSoC SINGLE CHIP TEMPERATURE CONTROLLER DESIGNFig.2 shows the PSoC designer screen for the embedded single chip (8 pin PSoC chipCY827143) temperature controller design project 1. Left side of the screen shows the settingsof global resource and user module parameters along with pin connectivity configuration. Middleportion of the screen shows the analog and digital blocks user module placement. Top portionof the screen shows the selected user modules for this project. Right side of the screendescribes the pin connectivity configured in the design. In this novel single chip design,thermocouple (TC) signal has been amplified by a programmable gain amplifier (PGA) placedin the PSoCs analog block. The amplified TC signal has been fed in to a 12 bit Analog-todigital(ADC) user module programmed in the PSoC chip, which includes both analog anddigital blocks for its functionality by PSoC designer programming. The converted digital dataof the amplified TC signal has been fed to the UART user module for serial communicationwith Personal Computer. The UART user module placed in the PSoC chip, automatically getsplaced in two digital blocks of PSoC chip, transmitter (TxD) and receiver (RxD) for PCs serialcommunication. A pulse width modulator (PWM), placed in the PSoC digital block, sets aserial pulse width modulated TTL pulses in response to the PID control function for thedeviation in set and measured temperature. This will in turn controls the optically coupledsolid state relay (SSR) driving the AC line power connected to the load/furnace 3,4. Themenu driven window based virtual instrument control program senses the temperature, via,thermocouple, TC amplifier, 12-bit ADC and UART communication block of PSoC chip andevaluate the control functions like P,I,D, linear heating, on-sweep and sets the pulse width ofPWM in a PSoC chip via UART block in a serial communication.An embedded single chip temperature controller designFig. 3 : Single PSoC chip Temperature controller design54Fig.3. shows the connectivity of a single PSoC chip design with solid state relay (SSR)and USB port via, serial-to-USB converter cable for communication with PC. The SSR, actsas AC power controller for controlling the furnace power, has been activated by the PWMpulses from PSoC chip. The menu driven virtual instrument control program works in windowenvironment interacts with the embedded design for sensing, controlling and acquiring thetemperature data. On-line plotting of acquired temperature data also carried out by the VIprogram.5. CONCLUSIONA simple and cost effective embedded temperature controller has been designed, fabricatedand tested successfully for its functionality. This compact designs permits the user to selectany type of control function through its virtual instrument program, written in LabVIEW7.1, and works under window environment. This design can be directly connected to PCscom port or USB port via USB-to-serial converter cable, the SSR power controller modulecan be connected on the furnace stand. The optically isolated power controller provides safeoperation without damaging the interfacing intelligent controller.6. REFERENCES1. J. Jayapandian. Current Science, Vol 90. No.6. 25th March 2006. p.765-770.2. National Instruments LabVIEW user manual.3. J. Jayapandian. Design Briefs. Electronic Design Magazine. A Penton Publication.New Jersey,USA.ED Online ID #5687. September 15, 2003.4. J. Jayapandian et.al. J. Instrum. Soc. India 33 (2) 75 80 (2003).J. Jayapandian and Usha Rani Ravi