#The Fifth Lichuang Electronic Design Competition#Pocket USB serial port oscilloscope

Note: This is a required field. [Please fill in during the registration stage↓]   1. Self/Team Introduction I am a software engineer and an amateur electronics enthusiast, with expertise in wireless transmission and smart home. I have been engaged in IoT software development for more than ten years.   2. Briefly introduce the project 1) The project is a pocket USB serial port oscilloscope, a small pocket oscilloscope specially prepared for electronic enthusiasts, maintenance engineers, and on-site installation personnel. The oscilloscope is an electronic device slightly larger than a matchbox and smaller than a business card. Plug it into a mobile phone with OTG function through the USB interface to draw power, and use the mobile phone screen to display the waveform. It can also be plugged into the USB port of a computer to use the computer screen as an oscilloscope screen. It can not only collect the pulse waveforms of infrared remote control codes, wireless remote control codes and serial port data commonly used in smart home devices, but also collect analog waveforms such as audio waveforms. Its APP software can not only watch waveforms, but also record waveforms, analyze waveforms, and identify waveform data. For analog waveforms, calculations such as Fourier transform can also be performed. 2) The collection accuracy is: the sampling rate of analog quantity collection is 80KHZ, the minimum signal voltage is 0.1mV; the pulse digital quantity collection is 1MHZ (1 microsecond) [Please fill in during the competition stage↓]   1. Describe the project details for a smart home project , often need to be compatible with equipment communication from different manufacturers. For example, Dongjia’s smart curtains and Xijia’s smart switches. Each company has its own communication protocol, and the simplest method of compatibility is to send the same waveform as it. Most of the common digital oscilloscopes on the market can only collect waveforms for a short period of time. To capture a waveform, it often requires the cooperation of two people and repeated many times to capture it. Therefore, I want to make a simple and practical pocket oscilloscope specially used for wave capture and analysis.

    This oscilloscope is composed of four major parts: pre-operational amplifier, MCU integrating AD conversion, USB serial port chip, and waveform generator. The operational amplifier samples the LM358 single power supply 5V powered operational amplifier chip to achieve 120 times signal amplification. Taking into account the attenuation of the signal by some resistors, a two-stage operational amplifier forms a 1000-fold signal amplification. The MCU uses STC15W404AS microcontroller, which has 4-channel 10-bit ADC converters and a conversion frequency of 80KHz. The converted data is transmitted to the USB to serial port chip through the serial port. The USB to serial port chip uses CH340G, which is low in price and has stable performance. The serial port baud rate is 921600. For the sake of low cost, this oscilloscope does not use a screen and uses the screen of a mobile phone or computer for display. The data is transferred to the mobile phone via USB, and the mobile APP processes and displays the data. At present, only Android mobile APP and Windows system application software have been developed. iOS is not currently supported. The main functions of the software include: waveform display, recording waveform, time measurement, voltage measurement, waveform identification, comparing waveforms, Fourier transform, and saving waveforms.   2. Describe the challenges faced by the project and the problems it solves. The difficulty of the project is APP development, which is heavy workload and difficult. The hardware aspect is the limitation of USB serial port data transmission speed. At first, wifi was used for transmission, but the stability was not as good as USB. In addition, considering the power supply issue, it was finally decided to use a USB serial port chip, which is simple and cheap. The second difficulty is the problem of signal strength adjustment. Signals of different strengths require different amplification factors. After the amplification factor of the op amp is fixed, just use resistors to attenuate the signal. At first I used the band switch to adjust it, but it was too big, and the APP didn't know which level the user had adjusted to, so it couldn't automatically calculate the voltage value. Later, I used the CD4051 electronic switch. The software can know which gear it is currently in, but the fatal problem is that small signals cannot pass through the CD4051. Finally, I thought of a double potentiometer. One is used to adjust the signal strength, and the other is connected to VCC. When adjusted to different positions, different voltages will be output. The voltage is converted into numbers using ADC, and the APP will know where the current potentiometer is adjusted. Now you know the voltage attenuation coefficient, and the APP can automatically calculate the voltage value.   3. Describe the key points involved in the hardware and software parts of the project   4. Display the project material list   5. Upload project pictures 5.1. Print the competition logo picture on the PCB. Failure to do so will be considered as giving up the competition 5.2. Other pictures of the project* 6. Demonstrate your Project and recorded into video upload 6.1, video upload competition official website 6.2, B station video title and link team introduction  https://www.bilibili.com/video/BV1eT4y1w7P4/   project introduction  https://www.bilibili.com/video/ BV1Rp4y1Y7TZ/   < span class="colour" style="color: rgb(68, 68, 68);">Function Demonstration & Performance Test < /span> https://www.bilibili.com/video/BV1854y127iL/ < br > < br> Notes: ①: Video requirements: Please shoot horizontally, the resolution is no less than 1280×720, the format is Mp4/Mov, the size of a single video is limited to 100M; ②: Video upload: please upload to the official website of the competition and At Station B ( www.bilibili.com ), the top 10 most popular projects at Station B will receive cash rewards of 1,000-5,000 yuan, and other uploaded projects will receive 100 yuan Lichuang Mall no-threshold coupons; ③: Video title: The 5th Lichuang Electronic Design Competition : {Project name}-{Video module name}; such as the 5th Lichuang Electronic Design Competition: "Autonomous Driving" project - team introduction.

  7. Whether it is published publicly for the first time 7.1. Whether the project has been published or won an award before. Please indicate that this is the first time the project has been published. 7.2. If the project is optimized on the original basis, please describe the optimization part   . 8. For open source documents, please see the attachment* 9. References

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