# Sixth Lichuang Electric Competition# Small oscilloscope based on HK32F103RBT6

  Main performance parameters of the oscilloscope:

1. Maximum real-time sampling rate: 1Msps

2. Accuracy: 12-bit ADC sampling

3. Analog bandwidth input: maximum 200KHz

4. Both vertical and horizontal positions are adjustable, with instructions

5. Input impedance: 0-2MΩ

6. Maximum input voltage: ±16Vpp (probe multiple is 10:1), ±150Vpp (probe multiple is 100:1)

7. Signal coupling method: DC/AC

8. Horizontal time base range: 1 μs-1s (progressively follows the 1-2-5 method)

9. Vertical level range: 20mV-100V (progressively follow the 1-2-5 method)

10. There are two triggering methods, rising and falling edges.

11. The trigger level position is adjustable and has an indication.

12. With waveform hold function (HOLD)

13. The oscilloscope comes with a 1KHz/3.3V square wave test signal source output (used for the oscilloscope to adjust probe compensation). This signal source is shared with the LCD backlight. The brightness of the LCD backlight is controlled by adjusting the PWM square wave duty cycle.

14. With waveform parameter display: frequency, period, pulse width, duty cycle, maximum value, minimum value, average value

15. All settings are automatically saved and will automatically restore to the last used state after being turned off and turned on again.

This oscilloscope uses the HK32F103RBT6 Hangshun chip as the core main control microcontroller, and the screen uses a 2.8-inch TFT LCD screen

The following is an analysis of the pre- and post-stage circuits of the oscilloscope:

  The front-end resistor divides the attenuation circuit. Generally, oscilloscopes must have front-end attenuation, because when measuring large voltages, the voltage range that the processor can receive is limited. For example, the ADC acquisition port voltage input range of the HK32F103RBT6 used here can only be 0. -3.3V only, the front-end adjustment circuit of this oscilloscope is divided into two attenuation ratios 10:1 and 100:1; for example: if the signal voltage value on the north side is 5V and the selected gear is 10:1, then when When the signal under test passes through switch S1, the signal voltage is only 0.5V; if the selected gear is 100:1, then the signal voltage value when the signal under test passes through switch S1 is only 0.05V; other measured signal voltage values ​​are the same. reason.

  The switch S1's Select, AC gear will filter out the DC component of the signal and only retain the AC component of the signal; DC gear will not filter any signal.

 The schematic diagram is as follows:

  The following is the schematic diagram of the post-stage part of the ADC conditioning circuit: here, the small signal attenuated by the pre-stage is amplified again so that the microcontroller can receive the correct 0-3.3V voltage; if the 5V signal passes through the pre-stage 100: After the 1 gear, it becomes a 0.05V voltage signal to the subsequent stage, and this 0.05V voltage will be amplified 60 times before being collected by the ADC of the microcontroller. If it is not amplified, the 0.05V is directly given to the ADC. Microcontroller acquisition will cause large noise fluctuations and is not conducive to the original display of the waveform; as for how many times to amplify the signal voltage, it is selected by the three combinations of S0, S1 and S2 of the 74HC4051 chip through the user buttons V+ and V- Which channel to use, choose 1 from 8 channel control, please check the chip manual of 74HC4051 for details.

 This small handheld oscilloscope only has a bandwidth of 200KHz, but it is good for measuring low frequencies or situations with low requirements. It can also be used to initially learn how to use an oscilloscope.

Open source agreement:

GPL 3.0  

This project is for open source learning and strictly for commercial purposes. Once discovered, legal responsibility will be pursued

The source code of this project is not made public for the time being, only the corresponding burning file (.hex file) is provided.