Design of the Data Acquisition System Based on STM32ABSTRACTEarly detect ion of failures in machi nery equipme nts is one of the most importa nt concerns to industry. In order to monitor effective of rotating machinery, we developme nt a micro-c on troller uC/OS-II system of sig nal acquisiti on system based on STM32 in this paper. we have give n the whole desig n scheme of system and the multi-cha nnel vibrati on sig nal in axis X, Y and Z of the rotary shaft can be acquired rapidly and display in real-time. Our system has the character of simple structure, low power con sumpti on, mini aturizati on.Keywords: STM32; data acquisition; embedded system;uC/OS-ll;1.1. I ntroductionThe real-time acquisition of vibration in rotating machinery can effectively predict, assessa nd diag nose equipme nt operati on state, the in dustry gets vibratio n data acquisiti on Rapidly and an alysis in real-time can mon itor the rotati ng mach inery state and guara ntee the safe running of the equipme nt. I n order to preve nt failure, reduce maintenance time, improve the econo mic efficie ncy, The purpose of fault diag no sis system can detect these devices through the vibratio n sig nal acquisiti on of rotating machinery, and process the data acquisition, then it will make timely judgme nt of running state of equipme nt .While the data acquisiti on module is the core part of the fault diag no sis system [1-4].The practical applicati on in the in dustrial field, is the equipment operating parameters will be acquired to monitor equipment operati ng state. In traditi onal data acquisiti on systems, the data from acquisiti on card are gen erally send into the computer, and specific software will be developed for the data acquisition. The main contribution of this paper has designed the STM32 platform with ARM tech no logy, that has become a traditi onal main stream tech no logy in embedded systems, and the collect ing data toward the directi on of high real-time, multi-parameter,high-precision, while data storage become large capacity, more mini aturizati on andportable, and the developme nt of multicom muni cati on mode and Iong-distanee for data transmission. So as to meet the actual acquisition system multitask ing requireme nts, this article has desig ned based on STM32 micro-co ntroller uC/OS-ll system of sig nal acquisiti on system. Therefore, in order to meet the actual acquisiti on system multitask requireme nts, this no velty of this article has desig ned a sig nal acquisiti on system in micro-c on troller uC/OS-ll based on STM32.2. Architecture of data acquisition systemData acquisiti on as key tech no logy for mon itori ng equipme nt, rece ntly a lot of work has been done on it. An embedded parallel data acquisition system based on FPGA is Optimized designed which will make it reasonableto divide and allocatehigh-speed and low-speed A/D [5]. I nstead, it has use a high-speed A/D converter and Stratix II series of FPGA for data collection and processing, in which the main contribution is used of the Compact Peripheral Component In terc onn ect, the system has the characters of modularizati on, sturd in ess and scalability [6].But remote control will be needed in Special Conditions, this paper introduce the embedded operating system platform based on Windows CE and uC/OS-II to desig n a remote acquisiti on and con trol system with the GPRS wireless tech no logy [7-8]」n order to achieve the data shari ng of multi-user, it has build the embedded dyn amic website for data acquisiti on man ageme nt and dissem in ati on with the ARM9 and Linux operation system [9].A data collection terminal devices is designed based on ARM7 microprocessor LPC2290 and embedded real-time operati ng system uC/OS-II to solve the real-time acquisiti on of multicha nnel small sig nal and multi-cha nnel tran smissi on[ 10].O n the other han ds, two parallel DSP-based system dedicated to the data acquisiti on on rotati ng machi nes, and the inner sig nal con diti oner is used to adapt the sen sor output to the in put range of the acquisiti on, and the n sig nal post-process in gby the desig n software, while the most frequently structure is to use DAS andFPGA-based, and such programs are also depe ndent on the DAS cost.In order to meet market requireme nts of low power con sumpti on, low cost, and mobility, Fig.1 in this paper presents the design overall structure diagram of data acquisiti on system. Through SPI in terface, the system gets the data collectio n with three axis accelerati on sen sori nto the STM32 con troller of inner A/D conv ersi onmodule with 12-bit, this process is non-interfering parallel acquisition. Our system uses 240x400 LCD and touch screen module real-time to display the collected data in real time.Fig. 1 Hardware Framework of System2.1. STM32 micro-controllerA 32 bit RISC STM32F103VET6, used as the processor in our system, compared with similar products, the STM32F103VET6 work at 72MHZ, with characters of stro ng performa nee and low power con sumptio n, real-time and low-cost. The processor in cludes: 512K FLASH, 64K SRAM, and it will commu ni cate by usi ng five serial ports which con tai n a CAN bus, a USB2.0 SLA VE mode and a Ethernet in terface, what s more two RS232 ports are also in cluded. The system in our paper exte nd theSST25VF016B serial memory through the SPI bus in terface, that will regard as the temporary storage whe n collect large nu mber of data, furthermore, we have the A/D converter with 12 bits resolution, and the fastest conversion up to 1us, with 3.6 Vfull-scale of the system .In additi on to desig n of the system power supply circuit, the reset circuit, RTC circuit and GPIO port to assurancesystem needs andno rmal operati on.2.2. Data acquisitionThe machi ne state is no rmal or not is mainly depe nded on the vibrati on sig nal. In this paper, to acquire the vibration data of rotating machinery rotor, we have used vibrati on accelerati on tran sducers MMA7455L which could collect the data from axis x, y, and z of the company of Free-scale. The kind of vibration acceleration transducers has advantage of low cost and small size, high sensitivity and large dynamic range with small interferenee. MMA7455L is mainly consists of gravity sensing unit and signal conditioning circuit composition, and this sensor will amplify the tiny data before sig nal preprocess in g. In data acquisiti on process of our system, the error of sampling stage is mainly caused by quantified, and the error is depended on the bits of the A/D converter ,when we regard the maximum voltage as V max , the AD converter bits is n, and the quantization Q = V max/2n, then, the quantization error is obeyed uniformdistribution in [- q / 2, q / 2] [13].AVhik e"is averaae eixor. is enor variance . and —is SNR* 」 " NThe designed STM32 could built at most three 12-bit parallel ADC in this paper , which theoretical in dex is 72dB and the actual dyn amic range is betwee n 54 to 60dB while 2 or 3 bits is impacted by noise, the dynamic range of measurement can up to 1000 times with 60dB. For the vast majority of the vibration signal, the maximum sampli ng rate of 10kHZ can meet actual dema nd, and the higher freque ncy of collecti on is gen erally used in the 8-12 bits AD, therefore one of con tributi on of this work is to (2) ⑶⑷I ep(e)de = OS V max2V max3Pinax 、—宀対-=—= >12V2—1£12choose a built-in 12-bit A/D to meet the accuracy of vibration signal acquisiti on and lower cost in this experime nt.3. Software design3.1. Transplantation of C/OSIn order to ensure real-time and safety data collection requirements, in this system, a kind of RTOS whose source code is ope n and small is proposed. It also can be easily to be cut dow n, repotted and solidified, and its basic functions in clud ing task management and resource management, storage management and system management. The RTOS embedded systemcould support 64 tasks, with at most 56 user tasks, and four tasks of the highest and the lowest priorities will be reta ined in system. The uC/OS-II assig ns priorities of the tasks accordi ng to their importa nee, the operation system executive the task from the priority sequenceand each task have in depe ndent priority. The operati ng system kernel is streamli ned, and multi-task ing fun cti on is well compared with others, it can be tran spla nted to processors that from 8-bit to 64-bit.The transplant in the system are to modify the three file system structure:OS_CPU_C.H OS_CPU.C, OS_CPU_A.ASM. Main transplantation procedure is as follows:A. OS_CPU_C.HIt has defi ned the data types, the len gth and growth direct ion of stack in the processor. Because different microprocessors have different word length , so theuC/OS-II tran spla ntati on in clude a series of type defi niti on to en sure its portability, and the revised code as follows:typedef un sig ned char BOOLEAN;typedef un sig ned char INT8U;typedef signed char INT8S;typedef un sig ned short INT16U;typedef sig ned short INT16U;typedef un sig ned int INT32U;typedef sig ned int INT32S;typedef float FP32;typedef double FP64;typedef un sig ned int OS_STK;typedef un sig ned int OS_CPU_SR;Cortex-M3 processor defi nes the OS_ENTER_CRITICAL () andOS_EXIT_CRITICAL () as ope ning and clos ing in terrupt, and they must set to 32 bit of the stack OS_STK and CPU register len gth. In additi on, that has defi ned the stack poin ter OS_STK_GROWTH stack growth direct ion from high address to lower address.B. OS_CPU.CTo modify the function OSTaskStklnit() according to the processor, the nine rema ining user in terface fun cti ons and hook fun cti ons can be n ull without special requirements, they will produce code for these functions only when theOS_CPU_HOOKS_EN is set to 1 in the file of OS_CFG .H. The stack initialization fun cti on OSTaskStk Init () retur n to the new top of the stack poin ter.OS_CPU_A.ASMMost of the tran spla nt work are completed in these docume nts, and modify the followi ng functions.OsStartHighRdy() is used for running the most priority ready task, it will be resp on sible for stack poin ter SP from the highest priority task of TCB con trol block, and restore the CPU, the n the task process created by the user start to con trol the process.OSCtxSw () is for task switch ing, When the curre nt task ready queue have a higher priority task, the CPU will start OSCtxSw () task switchi ng to run the higher priority task and the curre nt task stored in task stack.OSIntCtxSw () has the similar function with OSIntSw (), in order to ensurereal-time performa nee of the system, it will run the higher priority task directly whe n the in terrupt come, and will not store the curre nt task.OSTickISR () is use to handle the clock interrupt, which needs interrupt to schedule its impleme ntati on whe n a higher priority task is wait ing for the clock sig nal.OS_CPU_SR_Save () and OS_CPU_SR_Restore () is completed to switch in terrupt while en teri ng and leav ing the critical code both functions impleme nt by the critical protectio n fun ctio n OS_ENTER_CRITICAL () and OS_EXIT_CRITICAL ().After the completion ofthe above work, uC/OS-ll can run on the processors. 3.2. Software architectureFig.2 shows the system software architecture, so as to display the data visualized,uC/GUI3.90 and uC/OS-II is transplanted in the system, our system contains six tasks such data acquisiti on, data tran smissi on, LCD display, touch scree n driver, key-press management and uC/GUI interface.First of all, we should set the task priority and the task scheduling based on the priority. It needs complete the required driver design before the data acquisition, such as A/D driver, touch panel driver and system initialization, while the initializations include: hardware platform initialization, system clock initialization, interrupt source configuration, GPIO port configuration, serial port initialization and parameter configuration, and LCD in itializati on. The process is that the cha nnel module sent sampli ng comma nd to the AD channel, then to inform the receiver module it has been sent the sample start comma nd, the receiver module is ready to receive and large data will store in the storage module, after the completion of the first sampling, channel module will send the complete comma nd of sampli ng to the receiver module, the receiver sends an in terrupt request to the storage module to stop the data stori ng, the n the data will display on the LCD touch scree n. The data acquisiti on process show n in Fig.3Hui-fti Zhtmg tiiui Karif* / Proceditt Cotripufer Scienct! 17『20”J 222 - 228Fig - SofhvBtre Architecture of SyMem Tig 3 Data Acqm；＞ition of FlowChait4. ExperimentsThe experiment of the embedded system has been done and data acquisitioncomes from the accelerati on of MMA7455L, which is in stalled on the bench of rotat ing mach ine. The data acquisiti on have displayed as show n in Fig.4 and Fig.5, the system can select three channels to collect the vibration signal from the three directi ons of X, Y and Z-axis , and in this paper the sampli ng freque ncy is 5KHZ and we have collect the vibration signal from normal state of unbalaneed state at the same channel. The result shows that our system can display real-time data acquisition and5. Conclusion This paper has designed an embeddedsignal acquisition system for real time according to the mechanical failure occurred with high frequency of in the rotatingmachines. The system is based on a low cost microcontroller, Vibration signals is picked by the three axis accelerati on sen sor which has the performa nee of low cost and high sen sitivity, and the acquisiti on data from axis x, y, and z. We have desig ned the system hardware structure, and an alyses the work ing prin ciple of data acquisiti on module. The proposed system of uC/OS-ll realize the data task management and scheduling, and it is compacted with structure and low cost, what's more the system collects the vibration signal and analysis in real-time of the rotating machines, and then quickly gives diag no stic results. AcknowledgementsThis work was supported by The Nati onal Natural Scie nee Foun dati on of China (51175169); Chi na Natio nal Key Tech no logy R&D Program(2012BAF02B01); Pla predict the prelimi nary diag no sis rapidly. Fig.4 Noimal Dntn Acquisition Fi^ ,5 LJiibalance Data Acqmsihonnned Scie nee and Tech no logy Project of Hunan Provin ce(2009FJ4055);Scie ntific Research Fund of Hu nan Provi ncial Education Departme nt(10K023). 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