tag 标签: NI

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  • 热度 2
    2020-2-21 16:44
    296 次阅读|
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    探测技术对于高品质的示波器测量来说,是非常重要的。而探头通常是示波器测量链中的第一环。如果探头的性能不足,就会在示波器上看到失真讯号或误导讯号。为测试应用选择恰当的探头是执行可靠测量的第一步。而如何使用探头,也会影响执行精确测量的能力,以至于影响获得有用的测量结果。本文将透过 8个重要秘诀,帮助工程师为自己的应用选择适当探头,提高示波器探测能力,并避免最常见的探测陷阱。 图一 : 选择恰当的探头是执行可靠测量的第一步。而如何使用探头,也会影响获得有用的测量结果。 秘诀 1 无源探头或有源探头 对于低于 600MHz的中低频测量来说,高阻抗无源探头是很好的选择。这些探头坚固耐用且价格经济,具有大于300V的宽动态范围和高输入阻抗,因此可与示波器的输入阻抗相匹配。不过,和低阻抗无源探头或有源探头相比,无源探头具有更高的电容负载,而且频宽较低。总之,对于绝大多数类比或数位电路的通用除错和故障诊断来说,高阻抗无源探头都是一个极好的选择。 对于在宽频范围上大于 600MHz需要执行精确测量的高频应用来说,最好选用有源探头。有源探头比无源探头价格较高,并且其输入电压有限,但是由于它们的电容负载显着降低,因而能更精确地观察快速讯号。 秘诀 2 使用双探头检查探头负载 探测电路之前,先将一个探头连接到电路上的一点,然后再将第二个探头连接到同一点。在理想状况下,会看到讯号无任何变化。如果讯号产生变化,这个变化是由探头负载引起的。在理想状况下,示波器采用无扰线(具有无限的输入电阻、零电容和零电感)连接到待测电路,它能对待测讯号执行精确复制。但在现实世界中,探头是测量的一部分,它会向电路载入负载。 如欲检查探头的负载效应,首先要将探头连接到待测电路或一个已知的步进讯号,另一端连接到示波器的输入端。在示波器显示幕上观察此轨迹,然后保存,再在显示幕上调用以使迹线保留在显示幕上执行比较。之后可将相同类型的另一个探头连接到同一探测点,观察在使用两个探头执行探测时原始迹线有何变化。为了更隹执行探测,可能需要对探测执行调整,或者使用较低负载的探头。 秘诀 3 使用前的探头补偿 大多数探头在设计时,都和特定示波器型号的输入相匹配。不过,各个示波器之间也是略有差别,甚至在同一示波器的不同输入通道之间也有差别。所以在将探头连接到示波器的输入端之前,一定要确保首先检查探头补偿,因为此探头先前可能已经过调整,以便和不同的输入相匹配。 为了解决这个问题,大多数无源探头都采用内建补偿 RC分压器网路。探头补偿是调整RC分压器的过程,以使探头维持在额定频宽上的衰减率。如果示波器能够自动补偿探头性能,使用该功能将会非常有用。否则,可使用手动补偿来调整探头的可变电容。大多数示波器在前置面板上都可提供方波叁考讯号以对探头提供补偿。 秘诀 4 低电流测量秘诀 随着当前电池供电设备和积体电路变得越来越注重环保和高效能,工程师迫切需要高灵敏度的低电平电流测量能力,以确保电流消耗处于可接受的范围之内。需要精确测量功耗的主要应用,是无线行动设备和消费类电子产品等使用电池供电的应用。为了尽量延长电池的使用时间,工程师需要最大限度降低产品在整个使用寿命中的功耗。功率定义为 P=V×I。降低设备功耗的主要方法是在电源电压固定不变的情况下,减少设备的平均电流消耗。 测量由电池供电的行动设备的电流消耗,最主要的挑战是电流讯号的动态范围非常宽。行动设备通常需要在活动状态,与闲置或待机电流模式之间来回切换。可是,这种方法并不适合测量从不到 1毫安培快速变到几安培的小电流, 因为钳形电流探头的动态范围和灵敏度都非常有限,仅有几毫安培。而且,为获得更精确的测量,工程师必须不定期地对探头执行消磁处理,以消除探头核心的残余磁性,并补偿钳形电流探头的直流偏置。 秘诀 5 使用差动探头执行安全浮动点测量 示波器使用者经常需要执行浮动点测量。在这种测量中,任何测量点都不能潜在接地。在执行标准示波器测量时,探头连接到讯号点,探针接地引线连接到电路接地,此时,示波器实际测量的是测试点和接地之间的讯号差。大多数示波器都将其讯号接地终端(或 BNC介面的外壳)连接至防护接地系统。此举可使示波器上的所有讯号均有一个共同的连接点。基本上,所有示波器测量都是相对于「接地」来说的。本质上,将接地连接器连接到任何一个浮动点都可使探测点接地,这常常造成尖峰或电路故障。那么应如何应对这种浮动点测量问题呢,目前执行浮动点测量有一个很流行,但却不太可取的解决方案,那就是AB技术,它使用两个单端探棒和示波器的运算函数来执行浮动点测量。 秘诀 6 检查共模抑制 探测时最易产生误解的问题之一,是共模抑制可能会影响测量品质。无论是单端探棒还是差动探棒,将两个探针均连接到待测物的接地,然後观察萤幕上是否有任何讯号显示都是值得的。如有讯号显示,该讯号显示的就是由于缺少共模抑制而引起的讯号受影响程度。测量由源头而非讯号造成的共模杂讯电流,可从待测物的接地流经探棒接地,直至探棒电缆遮罩。共模噪音源可能在待测物内部,也可能在其外部,例如电源线杂讯、 EMI或ESD电流。单端探棒的长接地引线可能会使该问题变得非常明显。单端探棒常常会遭到缺少共模抑制的影响。差动主动探棒则可提供更高的共模抑制比,通常可高达80dB(10,000:1)。 秘诀 7 检查探头耦合 在将探头连接至讯号时,用手抓住探头电缆并绕圈移动。如果萤幕上的波形发生严重改变,那就说明能量就已耦合到探头遮罩,产生了这个改变。透过使用探头电缆上的磁芯来降低电缆遮罩的共模杂讯电流,可能有助于提高探测精准度。探头电缆上的磁芯会生成一系列的阻抗与导体中的电阻并联。增加探头电缆的磁芯对讯号几乎没什么影响,因为讯号通过中心导体的核心并沿着遮罩的核心返回,致使没有净讯号电流经过核心。 因此,电缆磁芯的位置非常重要。为方便起见,可尝试着将磁芯安装在示波器一端。这将使探头变得更轻、更易于操作。不过,在将磁芯安装到电缆的探头介面端时,磁芯的有效性将会大大降低。减少单端探头接地引线的长度将会有 一定的帮助作用,转而采用差动探头是最有效的措施。很多用户都不能理解探头电缆环境的改变会造成测量结果的改变,尤其是在执行高频测量时,它会造成测量可重复性和测量品质的下降。 秘诀 8 阻尼谐振 探头性能受到探头连接的高度影响。由于设计中讯号速度的提升,因此在连接示波器探头时可能会发现更多过冲、振荡和其他扰动。探头会在与元件的连接位置形成一个谐振电路。如果谐振位于示波器探头频宽内,确定测量扰动源于电路或是探头将变得十分困难。 应用方案 是德科技 Infiniium V系列示波器 是德科技:「我们让开发工程师能够精准洞察所量测到的信号。」 全球示波器拥有 12亿美元的市场规模,如此大的一块饼,当然也吸引了许多厂商竞相开发更好的产品,来获取更大的商机。而在高阶示波器市场上,是德科技也持续扮演着领导者的角色。面对高速数位讯号测试需求不断提升的情况下,是德科技也推出全新的Keysight Infiniium V系列示波器,来补足高阶示波器市场的最後一块拼图。 Keysight Infiniium V系列问世後,工程师便可又快又准确地执行所有测试,进而更快将新产品推出上市,并且增强对设计品质的自信度。 泰克科技 DPO70000SX 70GHz ATI高效能示波器 泰克科技:「这是首见的高效能整合式 MSO系列产品。」 泰克科技推出 MSO70000系列混合讯号示波器,该公司表示,此为首见的高效能整合式MSO系列产品。这部仪器拥有多达二十个量测通道,可以4~20GHz的类比频宽和80ps 的数位通道时序解析度进行撷取。随着MSO70000的推出,泰克科技现在在市场上拥有完整的混合讯号示波器产品组合;提供十七款MSO机型,从可携式的MSO2000一直到市面上快速的 20GHz MSO72004混合讯号示波器。 MSO已成为嵌入式系统工程设计的首选工具,这个领域对建立类比与数位讯号的关联有强烈的需求。现今,网路交换器和资料伺服器等嵌入式系统正采用更快速的技术,因而需要更高效能的MSO。其他如高速串列与数位射频的应用领域,也需要完整的系统能见度。随着MSO70000系列的推出,泰克科技提供了良好的类比/数位撷取效能与多样化的探测方案。 罗德与施瓦茨 RTP示波器 中国台湾罗德与施瓦茨:「我们正式进军高阶示波器市场!」 R&S RTP系列在开发过程中,特别着重于量测精准度、速度和新技术,并完整地结合多种仪器功能,是研发过程中故障排除的绝隹选择,例如测试具快速数位介面或宽频无线射频传输介面的嵌入式元件。R&S RTP高效能示波器结合了讯号完整性与高撷取速率,在标准撷取模式下,每秒可量测一百万个波形,比其他同类示波器快一千倍以上,能帮助使用者更快地发现零星错误,并可即时补偿讯号源到示波器之间的传输损耗。 此外, R&S RTP 可满足高频应用量测需求,举凡航空、国防、汽车、工业和通讯等领域;同时亦适用高速数位介面测试如高速汇流排(USB、PCI Express、MIPI)、无线电或雷达等射频介面、DDR记忆体介面、电源管理元件,及简单的控制和编程汇流排。R&S持续致力于示波器市场的创新,透过发表新一代R&S RTP系列,R&S宣告正式进军高阶示波器市场。 NI PXI架构高速示波器 国家仪器:「 PXI架构可大幅缩短测试时间。」 NI高速示波器具有强大的仪器整合,再加上高输出PXI汇流排有助于缩短测试时间,非常适合高频宽自动化量测作业。NI高速示波器搭载了NI专利T-Clock同步化技术,可藉此建置高达34个相位同步1GS/s通道所组成的系统,并且进一步整合其他NI硬体,打造出完整的自动化混合式讯号测试系统。 大多数的自动化测试与多重工作台应用,均需要多类型的仪器,如示波器、讯号产生器、数位波形分析器、数位波形产生器,与切换器等。 PXI与NI模组化仪器既有的时序与同步化功能,可同步上述的所有仪器,且不需额外接线。PXI的模组化特性大幅提升了速度,且使用者不需再耗时操作,进而提高效率。
  • 热度 1
    2014-11-12 11:41
    268 次阅读|
    0 个评论
      美国国家仪器公司(National Instruments, 简称 NI)与南京航空航天大学(以下简称南航)能源与动力学院合作建立的“图形化系统设计大学生创新中心”(以下简称“创新中心”)举行了揭牌仪式。仪式由能源与动力学院动力工程系副主任张天宏教授主持,能源与动力学院院长陈伟教授, NI 南京地区销售经理胡嘉伟先生、NI华东华南区大学计划代表李甫成先生共同为联合实验室揭牌。   南航一直十分重视工程创新人才的培养, 能源与动力学院是南航历史最为悠久的院系之一,NI 图形化系统设计理念及相关软硬件平台被广泛应用于南航包括能源与动力学院、自动化学院、航空宇航学院、电工电子实验中心等多个院系的教学和科研中。 大学生创新中心的建立再一次体现了 NI致力于与国内一流工科高校合作的长期发展理念,也将进一步促进南航能源与动力学院与 NI 在创新型工程人才培养方面的多层次及全方位合作。   出席揭牌仪式的能源与动力学院院长陈伟教授对 NI 在南航多个教学和科研机构进行的深入合作表示支持与赞赏,NI 华东华南区大学计划代表李甫成先生对该联合实验室的未来规划及与能动学院的长期合作分别做了展望。未来,该大学生创新中心将主要服务于能源与动力学院本科及研究生的嵌入式控制系统、发动机控制、自动控制原理等相关课程实验,大学生创新创业活动,学生创新竞赛培训,学生毕业设计,辐射江苏地区的高校教师培训,LabVIEW认证等活动。   创新中心已配备数十套目前已经被成功应用在Rice University以及清华大学等国际一流大学大规模在线开放课程(MOOC慕课)的 NI myDAQ 便携式综合仪器平台,针对嵌入式测试与控制和大学生创新实践项目并成功应用在UC Berkeley等高校的MOOC口袋嵌入式平台NI myRIO,衔接高年级本科生与研究生并已被工业界广泛使用的工业级嵌入式测控平台NI Singleboard-RIO,这些平台不仅能满足现有课程的教学实验和开放式动手实践需求,还能为能源与动力学院的学生定制更多具有南航特色的新型实验内容。   揭牌仪式之后,来自NI院校市场部及销售部的企业代表与能动学院的相关课程及实验老师就相关软硬件设备的使用培训和该中心未来的管理机制进行了深入交流。 双方共同表示今后还将继续加强校企合作,充分利用该联合实验室的优良软硬件条件,为培养更多卓越的能源与动力领域工程创新人才服务。
  • 热度 2
    2014-2-20 18:12
    1062 次阅读|
    0 个评论
    If you ask engineers about their favourite childhood toys,  you're likely to hear a list of nostalgic staples that sparked innovation in all of us who went on to solidify our calling with the title "engineer." We loved these toys because they allowed us to think of an idea and then actually create it. But, what happens to these young innovators as they become engineering students and their ideas become more complex? Until recently, these students discovered that the gap between toys and industrial tools was an ocean of devices that either catered to their budding yet incomplete knowledge or provided the depth of technical functionality desired, but never both. Identifying and understanding this deficiency, National Instruments (NI) wanted to create a solution that would provide the ease of learning that students need, while also giving them the power to release their creative potential within the time constraints of a class. For over 30 years, NI has witnessed some of the world's most established engineering companies, as well as some game-changing innovators, like CERN and SpaceX innovate and create incredible systems using our test and measurement technologies. But what about the engineers of tomorrow? How do LEGO bricks and Tinker Toys progress to life-saving medical equipment or the next hybrid electric vehicle? For several years, NI has thought about this question and—in 2013—provided an answer by releasing a new product for students—NI myRIO. Inspired by the same technology NI has provided to industry customers for years, NI myRIO equips today's students with the tools of their future careers (click here to see a video). NI myRIO is based on the same LabVIEW RIO architecture as NI's industrially used NI CompactRIO and NI Single-BoardRIO products. These products combine a processor, FPGA, and I/O, and are fully programmable with LabVIEW. In fact, NI myRIO uses the same Xilinx Zynq All-programmable SoC technology found in NI's newest CompactRIO, the cRIO-9068. Complete with 40 digital I/O lines, 10 analogue inputs, 6 analogue outputs, onboard accelerometer, LEDs and programmable button, students get to leverage copious reconfigurable I/O and boast the use of NI's first WiFi-enabled RIO product all in a handheld device. But, the hardware is only half of the equation. Surely we can't expect students to jump into the same programming complexity as seasoned, professional engineers, right? Well, at NI, we agree. Fortunately, LabVIEW has provided the handshake between the possibilities of industry and the first-year college student. NI ships the FPGA of myRIO pre-defined with AI, AO, PWMs, Quad Encoder inputs, UART, SPI, and I2C. Of course, using LabVIEW FPGA, students can choose to change this shipping personality if a project warrants it (and yes, they can always revert back to the default). While the NI myRIO processor and FPGA can be programmed in the exact same manner as its industrial counterparts, we wanted to offer students some help to quickly access I/O out of the box. LabVIEW provides 12 configuration-based Express VIs specifically for myRIO that allow for instant access to the pre-defined FPGA I/O without the need for extensive programming. When students are ready expand their programming skills, they can view the underlying code of any myRIO Express VI and can begin using that code to program in a more advanced mode. All pre-built LabVIEW functionality for myRIO is open, meaning that a student has the option to explore even the lowest level handshake between processor and FPGA.   Students connect to their myRIO via USB (versus traditional Ethernet) or WiFi to deploy code and monitor results. The ultra familiar and ubiquitous USB connection removes the complexity associated with Ethernet connectivity and WiFi allows students to access their device remotely with their PC or tablet. Rounding out the device's flexibility, students can also choose to leverage Linux and C/C++ to program the hardware with the popular Eclipse IDE. When designing myRIO, NI engineers were adamant that students engage in real system design not upon graduation, but now. We specifically chose the features and massaged the user experience to transform engineering students into full-fledged system designers, even providing a free guide for incorporating common components. Knowing that this product would play a role in the classroom with leading universities around the globe, NI is rolling out courseware that will address competencies in Embedded Systems, Controls and Mechatronics based on NI myRIO. In fact, Rice University has already incorporated NI myRIO into their Modelling Dynamic Systems curriculum using the popular haptic paddle force feedback device. NI myRIO encourages students to let their ideas run wild and provides them with the hardware and software to get the job done. Based on NI's industry recognised RIO hardware, the latest gadget for young engineers is anything but a toy. Check out the latest Waterloo Labs video— The Paintball Picasso System . This system is controlled by the NI myRIO embedded controller and LabVIEW software that enables the system to be controlled is a variety of ways, including taking an image from a USB webcam in order to outline the person, shooting more than 10 paintballs per second. You may rest assured that no students were harmed in the making of this video. About the author As product manager for Controls, Robotics, Mechatronics, and Embedded (CRoME) on National Instruments' Academic Marketing team, Margaret Barrett is responsible for building awareness of NI's offerings in the university space for these application areas. Margaret is a five-year veteran at National Instruments, where she began her career as an Applications Engineer and later transitioned to managing a subset of the AE department. Before joining National Instruments, she attended Texas AM University where she earned a degree in biomedical engineering with an emphasis in biomechanics in addition to earning a minor in mathematics.  
  • 热度 1
    2014-2-20 18:12
    1044 次阅读|
    0 个评论
    Discussions on favourite childhood toys are likely to yield a list of nostalgic staples that sparked innovation in all of us who went on to solidify our calling with the title "engineer." We loved these toys because they allowed us to think of an idea and then actually create it. But, what happens to these young innovators as they become engineering students and their ideas become more complex? Until recently, these students discovered that the gap between toys and industrial tools was an ocean of devices that either catered to their budding yet incomplete knowledge or provided the depth of technical functionality desired, but never both. Identifying and understanding this deficiency, National Instruments (NI) wanted to create a solution that would provide the ease of learning that students need, while also giving them the power to release their creative potential within the time constraints of a class. For over 30 years, NI has witnessed some of the world's most established engineering companies, as well as some game-changing innovators, like CERN and SpaceX innovate and create incredible systems using our test and measurement technologies. But what about the engineers of tomorrow? How do LEGO bricks and Tinker Toys progress to life-saving medical equipment or the next hybrid electric vehicle? For several years, NI has thought about this question and—in 2013—provided an answer by releasing a new product for students—NI myRIO. Inspired by the same technology NI has provided to industry customers for years, NI myRIO equips today's students with the tools of their future careers (click here to see a video). NI myRIO is based on the same LabVIEW RIO architecture as NI's industrially used NI CompactRIO and NI Single-BoardRIO products. These products combine a processor, FPGA, and I/O, and are fully programmable with LabVIEW. In fact, NI myRIO uses the same Xilinx Zynq All-programmable SoC technology found in NI's newest CompactRIO, the cRIO-9068. Complete with 40 digital I/O lines, 10 analogue inputs, 6 analogue outputs, onboard accelerometer, LEDs and programmable button, students get to leverage copious reconfigurable I/O and boast the use of NI's first WiFi-enabled RIO product all in a handheld device. But, the hardware is only half of the equation. Surely we can't expect students to jump into the same programming complexity as seasoned, professional engineers, right? Well, at NI, we agree. Fortunately, LabVIEW has provided the handshake between the possibilities of industry and the first-year college student. NI ships the FPGA of myRIO pre-defined with AI, AO, PWMs, Quad Encoder inputs, UART, SPI, and I2C. Of course, using LabVIEW FPGA, students can choose to change this shipping personality if a project warrants it (and yes, they can always revert back to the default). While the NI myRIO processor and FPGA can be programmed in the exact same manner as its industrial counterparts, we wanted to offer students some help to quickly access I/O out of the box. LabVIEW provides 12 configuration-based Express VIs specifically for myRIO that allow for instant access to the pre-defined FPGA I/O without the need for extensive programming. When students are ready expand their programming skills, they can view the underlying code of any myRIO Express VI and can begin using that code to program in a more advanced mode. All pre-built LabVIEW functionality for myRIO is open, meaning that a student has the option to explore even the lowest level handshake between processor and FPGA.   Students connect to their myRIO via USB (versus traditional Ethernet) or WiFi to deploy code and monitor results. The ultra familiar and ubiquitous USB connection removes the complexity associated with Ethernet connectivity and WiFi allows students to access their device remotely with their PC or tablet. Rounding out the device's flexibility, students can also choose to leverage Linux and C/C++ to program the hardware with the popular Eclipse IDE. When designing myRIO, NI engineers were adamant that students engage in real system design not upon graduation, but now. We specifically chose the features and massaged the user experience to transform engineering students into full-fledged system designers, even providing a free guide for incorporating common components. Knowing that this product would play a role in the classroom with leading universities around the globe, NI is rolling out courseware that will address competencies in Embedded Systems, Controls and Mechatronics based on NI myRIO. In fact, Rice University has already incorporated NI myRIO into their Modelling Dynamic Systems curriculum using the popular haptic paddle force feedback device. NI myRIO encourages students to let their ideas run wild and provides them with the hardware and software to get the job done. Based on NI's industry recognised RIO hardware, the latest gadget for young engineers is anything but a toy. Check out the latest Waterloo Labs video— The Paintball Picasso System . This system is controlled by the NI myRIO embedded controller and LabVIEW software that enables the system to be controlled is a variety of ways, including taking an image from a USB webcam in order to outline the person, shooting more than 10 paintballs per second. You may rest assured that no students were harmed in the making of this video. About the author As product manager for Controls, Robotics, Mechatronics, and Embedded (CRoME) on National Instruments' Academic Marketing team, Margaret Barrett is responsible for building awareness of NI's offerings in the university space for these application areas. Margaret is a five-year veteran at National Instruments, where she began her career as an Applications Engineer and later transitioned to managing a subset of the AE department. Before joining National Instruments, she attended Texas AM University where she earned a degree in biomedical engineering with an emphasis in biomechanics in addition to earning a minor in mathematics.
  • 热度 4
    2010-9-30 13:29
    2308 次阅读|
    2 个评论
    今天上网看到ADI出了ADSP-BF50X Blackfin处理器和TI德州仪器出了TMS320C5514X,这两个几乎垄断DSP行业并且称霸模拟业界的厂商在新年又来了竞争,不敢想这俩芯片的性能能如此超过象,TMS320C551X居然带1024点硬FFT引擎,BF50X的12位AD能达到2M采样率,手都痒痒想玩玩,可一看两种开发板都是在200美元左右,对于国人目前的水平来说不是什么小数,看来也不是给咱们想玩的人玩的。   这也不足为怪,与之相比目前的ARM板子可也到达外国人眼中的萝卜白菜价格了,所以才会有那么多的孩子能勒紧裤腰带买上一块板子回来试试,而且这种趋势正在向好的方向发展,大学里孩子们最起码目前知道必须学些 ARM编程为了找工作,尽管目前有一窝哄的方式都学有时缺乏些理性,也是好事。 更多的希望则是这些模拟大厂也多出些真正面向中国的板子,别动不动来个几百个“刀”,对于中国想学习的人来讲真是放血。敢说目前国内会labview的人数量是最让NI高兴的数字,这是未来的市场啊。可再看看NI的方面,东西依然是那样贵,没有任何太多亲近中国的态度。我统计了一下,目前能用 labview开发ARM的人不是很多,关键一点就是NI要价太很,再加上配套原装开发系统也贵,就这样把一个在一般算法优势的开发ARM的机会和中国众多未来客户给割裂开了。   对于一个发展中的中国,目前我们最缺少的是过去可继承的一些和与西方世界平起平坐的机会。这就像今天我们的模拟设计和更多工程系统软件方面的劣势,坦白讲西方真的会白给我们平等的机会?西方世界哥本哈根为自己过去排放讨价和吵架泼妇一般的原因很明了,弱者很少能够得到真正的话语权。 在一种矛盾的心理上去理解落后,可能是对自己的尊重,但不应该承认这始终是进行时,应该让这种落后成为过去式,起码在我们尽可能少的几代能实现。需要更多的开发板,包括心理的开发板。
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