A visible light communication system

Abstract

This invention relates to the field of visible light communication technology and discloses a visible light communication system, including a signal transmitting module and a signal receiving module. The signal transmitting module includes an OFDM signal amplification circuit; the signal receiving module includes a photoelectric sensor and an ambient light sensor. One end of the ambient light sensor is connected to a microcontroller, and a level conversion circuit connects the ambient light sensor and the microcontroller. One end of the microcontroller is connected to a digital-to-analog converter (DAC), and the other end of the DAC is connected to a voltage amplifier. The ambient light sensor detects the illuminance, causing the signal receiving module to automatically adjust the gain of the voltage amplifier. This invention achieves a large visible light signal coverage area at the LED lamp end, and the receiving end has a certain degree of adaptive function and mobility, improving the user experience of visible light communication.

Description

Technical Field

[0001] This invention relates to the field of visible light communication technology, specifically to a visible light communication system. Background Technology

[0002] Visible light communication typically uses the rapid flashing of light-emitting diodes (LEDs) to transmit information, often employing white light, but other colors of visible light can also be used. Visible light communication does not require radio spectrum resources, produces no electromagnetic interference, and offers high security, making it significant in fields such as aviation, military, and medicine.

[0003] Currently, visible light communication is still an emerging technology with very few commercial applications. This is mainly because existing visible light communication products suffer from problems such as small coverage, short transmission distance, and poor mobility, which affect user experience.

[0004] The visible light communication system proposed in this scheme is based on phosphor-type LEDs. To address the shortcomings of existing technologies, improvements have been made in both signal transmission and signal reception. Therefore, we need to propose a visible light communication system. Summary of the Invention

[0005] The purpose of this invention is to provide a visible light communication system that enables a large visible light signal coverage area at the LED lamp end, provides the receiver with a certain degree of adaptive function and mobility, and improves the user experience of visible light communication, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a visible light communication system, comprising: Signal transmitting module and signal receiving module; The signal transmission module includes an OFDM signal amplification circuit, which comprises a chip U1, a variable resistor RP1, and a resistor R2. A resistor R9 is connected to the IN- pin of chip U1, with one end of resistor R9 connected to a capacitor C6, and the other end of capacitor C6 grounded. The variable resistor RP1 is connected between the IN- and OUT pins of chip U1. Resistors R4, R5, and R3 are connected to the IN+ pin of chip U1, with one end of resistor R3 connected in series with capacitor C1, one end of which is connected to the OFDM signal. One end of resistor R2 is connected to the OFDM signal, and the other end is grounded. Capacitors C7 and C8 are connected in parallel to the +Vs pin of chip U1, with the other ends of capacitors C7 and C8 grounded. A capacitor C4 is connected to the OUT pin of chip U1, with one end of capacitor C4 connected to a resistor R6. The amplified OFDM signal is output from the rear end of resistor R6.

[0007] The signal receiving module includes a photoelectric sensor and an ambient light sensor. One end of the photoelectric sensor is connected to a transimpedance amplifier, one end of the transimpedance amplifier is connected to a voltage amplifier, one end of the voltage amplifier is connected to a signal demodulation module, one end of the signal demodulation module is connected to a signal decoding module, one end of the ambient light sensor is connected to a microcontroller, a level conversion circuit is connected between the ambient light sensor and the microcontroller, one end of the microcontroller is connected to a digital-to-analog converter, and one end of the digital-to-analog converter is connected to the voltage amplifier.

[0008] Preferably, the ambient light sensor has an I 2 The ambient light sensor detects illuminance data via communication interfaces SCL and SDA. 2 The C communication interface is read out and used, allowing it to work with a microcontroller.

[0009] Preferably, the ambient light sensor is sensor U4, which is powered by a voltage regulator U5 at 1.8V. The VDD pin of sensor U4 is connected to the OUT pin of voltage regulator U5. The SDA pin of sensor U4 is pulled up to 1.8V by resistor R63. The VSS pin of sensor U4 is grounded. The GPIO2 pin of sensor U4 is connected to a grounded resistor R65. The GPIO1 pin of sensor U4 is pulled up to 1.8V by resistor R66. The SCL pin of sensor U4 is pulled up to 1.8V by resistor R64.

[0010] The voltage regulator U5, in conjunction with the external circuitry, converts 5V to the 1.8V required by the sensor U4. The GND pin of the voltage regulator U5 is grounded, and the IN pin of the voltage regulator U5 is connected to the 5V voltage. The IN pin of the voltage regulator U5 is connected to capacitors C67 and C68 in parallel, with the other ends of capacitors C67 and C68 grounded. The OUT pin of the voltage regulator U5 outputs 1.8V. The OUT pin of the voltage regulator U5 is also connected to capacitors C69 and C70 in parallel, with the other ends of capacitors C69 and C70 grounded.

[0011] Preferably, the I / O interface of the microcontroller is connected to a tri-color LED indicator, which includes a red LED D1, a green LED D2, and a blue LED D3. A resistor R70 is connected between the red LED D1 and pin 1 of the microcontroller, a resistor R71 is connected between the green LED D2 and pin 2 of the microcontroller, and a resistor R72 is connected between the blue LED D3 and pin 3 of the microcontroller. A resistor R67 is connected to the SDA bus of the microcontroller, a resistor R68 is connected to the SCL bus of the microcontroller, and a resistor R69 is connected to the INT input terminal of the microcontroller. The other ends of resistors R67, R68, and R69 are all connected to a 3V voltage.

[0012] Preferably, the voltage amplifier includes an amplifier U6 and an inductor L1 connected to an external 5V power supply. One end of the inductor L1 is connected to capacitors C22 and C33, C32 and C34, and C38 and C39 connected in parallel. The terminals of capacitors C22 and C33 are connected to the VPOS pin of the amplifier U6, the terminals of capacitors C32 and C34 are connected to the VPSO pin of the amplifier U6, and the terminals of capacitors C38 and C39 are connected to the VPSI pin of the amplifier U6.

[0013] Preferably, a capacitor C36 and a resistor R26 are connected in series between the OFST pin and the CNTR pin of the amplifier U6; a resistor R35 is connected to the VDBS pin of the amplifier U6; a resistor R38 is connected between the VPSI pin and the MODE pin of the amplifier U6; capacitors C28 and C41 are connected in parallel to the OPLO pin of the amplifier U6, with the other end of capacitor C28 grounded and the other end of capacitor C41 connected to a resistor R27; and capacitors C27 and C40 are connected in parallel to the OPHI pin of the amplifier U6, with the other end of capacitor C27 grounded and the other end of capacitor C40 connected to a resistor R27.

[0014] Preferably, the digital-to-analog converter and the microcontroller are connected via 1 2 C-bus communication, the digital-to-analog converter is converter U2, the 3V power supply of converter U2 comes from voltage regulator U3, the GND pin of voltage regulator U3 is grounded, the IN pin of voltage regulator U3 is connected to a 5V voltage, and capacitors C64 and C63 are also connected in parallel to the IN pin of voltage regulator U3. The other end of capacitor C64 and the other end of capacitor C63 are both grounded, and the OUT pin of voltage regulator U3 outputs 3V.

[0015] Preferably, the GND pin of converter U2 is grounded, a resistor R62 is connected to the SDA pin of converter U2, a resistor R61 is connected to the SCL pin of converter U2, and resistors R61 and R62 are connected to a 3V power supply. A capacitor C71 is connected to the VOUT pin of converter U2, and the other end of capacitor C71 is grounded. The A0 pin of converter U2 is grounded, and the VDD pin of converter U2 is connected to a 3V power supply. A capacitor C61 and a capacitor C62 are connected in parallel to the VDD pin, and the other ends of capacitors C61 and C62 are both grounded.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention achieves a large visible light signal coverage area at the LED lamp end, and the receiver has a certain degree of adaptive function and mobility, thereby improving the user experience of visible light communication. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of the OFDM signal amplification circuit of the present invention; Figure 2 This is a schematic diagram of the visible light communication receiver structure of the present invention; Figure 3 This is a circuit diagram of the ambient light sensor VD6283TX of the present invention; Figure 4 This is a circuit diagram showing the I2C bus and tri-color LED connection of the microcontroller in this invention; Figure 5 This is a circuit diagram for the 1.8V and 3V level conversion of the present invention; Figure 6 This is a circuit diagram of the AD8330 voltage amplifier of the present invention; Figure 7 The circuit diagram of the digital-to-analog converter (D / A) AD5311 of this invention is shown below. Figure 8 This is a flowchart of the microcontroller software of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1-8 The present invention provides a technical solution: a visible light communication system, comprising: Signal transmitting module and signal receiving module; In visible light communication, the signal to be transmitted is modulated (called the modulated signal) and superimposed on the constant DC current driving the LED, both of which are applied to the LED to make it emit light. This is equivalent to the modulated signal current modulating the constant DC current, and the current modulation index can be defined as m = Is / Ic (Equation 1), where Is is the modulated signal current and Ic is the DC current. Under constant conditions, the higher the current modulation index, the easier it is for the useful signal in the transmitted light to be detected by the photoelectric sensor at the receiving end. As can be seen from Equation 1, to increase the current modulation index, the amplitude of the constant DC current can be reduced, or the amplitude of the signal current can be increased. However, if the amplitude of the constant DC current is reduced, the illuminance of the LED will decrease. In visible light communication, LEDs usually also have an illumination function, and the illuminance cannot be too low. Moreover, experiments have shown that if the light generated by DC driving is stronger, it is more conducive to carrying the useful light signal to a farther distance. Therefore, to increase the current modulation index, the better way is to increase the amplitude of the modulated signal current. When the LED is used as a load, the voltage amplitude can be increased to increase the current amplitude.

[0020] Currently, the best signal modulation method for visible light communication is OFDM (Orthogonal Frequency Division Multiplexing), which is usually implemented using FPGA. The OFDM modulated signal output by the FPGA circuit is small, with a peak-to-peak value of less than 3V. If it is directly superimposed with DC, the current modulation is low, resulting in poor visible light communication performance. Therefore, an amplifier circuit needs to be added to the output of the FPGA.

[0021] To address the issue of low amplitude in OFDM modulated signals, the signal transmission module of this invention includes an OFDM signal amplification circuit. This circuit comprises a chip U1 and a variable resistor RP1. A resistor R9 is connected to the IN- pin of chip U1, with one end of resistor R9 connected to a capacitor C6, and the other end of capacitor C6 grounded. The variable resistor RP1 is connected between the IN- and OUT pins of chip U1. Resistors R4, R5, and R3 are connected to the IN+ pin of chip U1, with one end of resistor R3 connected in series with capacitor C1. One end of capacitor C1 is connected to the OFDM signal. One end of resistor R2 is connected to the OFDM signal, and the other end is grounded. Capacitors C7 and C8 are connected in parallel to the +Vs pin of chip U1, with the other ends of capacitors C7 and C8 grounded. A capacitor C4 is connected to the OUT pin of chip U1, with one end of capacitor C4 connected to resistor R6. The amplified OFDM signal is output from the rear end of resistor R6. Figure 1In this circuit, the OFDM signal comes from the pre-amplifier OFDM modulation module. Resistor R2 is connected between the OFDM signal and ground to match the impedance of the pre-amplifier circuit. Capacitors C1 and C4 are DC blocking capacitors. Resistor R3 is a current-limiting resistor. Resistors R4 and R5 form a voltage divider circuit, splitting the 12V power supply equally to obtain a 6V voltage applied to the non-inverting input of the OPA690. Capacitor C6, resistor R9, and variable resistor RP1 form a negative feedback loop. RP1 is an adjustable resistor, adjustable from 0 to 10KΩ. Capacitors C7 and C8 are filter capacitors for the 12V power supply. Resistor R6 matches the impedance of the subsequent stage; the amplified OFDM signal is output from the output after resistor R6.

[0022] like Figure 1 The OFDM signal amplification circuit shown has good amplification performance in the OFDM signal frequency band. The amplification factor (let's call it G) can be changed by changing the resistance value of the variable resistor RP1 as needed. The amplitude of the amplified undistorted OFDM signal can reach 10V.

[0023] G = RP1 / R9 (Equation 2) At the receiving end of visible light communication, photoelectric sensors such as APD (avalanche photodiode) or PIN-PD (P-type semiconductor-dump-N-type semiconductor photodiode) within the visible light wavelength range can be used to receive light and obtain a weak current. Then, a transimpedance amplifier circuit is connected to convert the current into a voltage. At this time, the voltage amplitude is small and insufficient to match the subsequent demodulation circuit. Therefore, an adjustable gain voltage amplifier is added. The amplified signal enters the signal demodulation module, and after decoding, the useful signal sent from the signal transmitter is finally obtained, completing the visible light communication process.

[0024] The experiment found that the illuminance received by the photoelectric sensor at the receiving end is directly proportional to the communication performance. In order to realize the adaptive processing of the illuminance of the light signal by the receiving circuit, the present invention sets an ambient light sensor next to the PIN-PD. The sensor is small in size and located close to the PIN-PD, so it can be approximated that the two receive the same amount of radiation.

[0025] Ambient light sensors can be divided into two categories: visible light full-spectrum detection and monochromatic light detection. The illuminance data obtained from visible light full-spectrum detection is similar to that obtained from a visible light illuminance meter. Let the illuminance data read by the system composed of a microcontroller and the ambient light sensor be Ai, and the illuminance data measured by a standard illuminance meter be Bi. There is a certain deviation between the two, denoted as Ci, which needs to be corrected to approximate zero. A standard light source can be used to simultaneously measure Ai and Bi at 100 selected locations. Data fitting can be performed to obtain the relationship between Ai and Bi. After the microcontroller reads the illuminance value from the ambient light sensor each time, the relationship between Ai and Bi is used to correct the illuminance. The corrected data is used to control the gain of the receiving circuit. For full-spectrum detection, the OPT3004 ambient light sensor can be used to measure the illuminance of white light.

[0026] Phosphor-based white LEDs use blue light to excite yellow phosphors to produce yellow light, which is then mixed to create white light. Current research in visible light communication generally agrees that yellow light responds slowly to signals, while blue light responds quickly. In visible light communication, blue light is the useful light, and a blue filter is typically used at the receiver to filter out blue light, allowing only blue light to be received. In this case, to more accurately determine the relationship between illumination and communication, a monochromatic light detector (such as a blue light detector) can be used for more targeted light detection.

[0027] In visible light communication systems based on phosphor LEDs, blue light is the useful light for communication. Therefore, the VD6283TX ambient light sensor can be selected. This device has independent red, green, blue, and visible light sensing channels, capable of measuring illuminance separately. It is suitable for red, green, blue, and white light potentially used in visible light communication. The VD6283TX has a built-in illuminance correction function; the correction parameters are stored in its OTP memory, and the corrected illuminance data can be read by a microcontroller. This invention uses the VD6283TX to detect blue light.

[0028] The ambient light sensor has I 2 The ambient light sensor detects illuminance data via communication interfaces SCL and SDA. 2 The C communication interface is read out and used, allowing it to work with a microcontroller.

[0029] A VD6283TX microcontroller is used to detect blue light, paired with a microcontroller and an ST capacitor C15W4K40S4. Because the microcontroller's SCL, SDA buses and I / O operate at 3V, while the VD6283TX's SCL, SDA buses and I / O operate at 1.8V, a level conversion circuit is required. Figure 5 .

[0030] The signal receiving module includes a photoelectric sensor and an ambient light sensor. One end of the photoelectric sensor is connected to a transimpedance amplifier, one end of the transimpedance amplifier is connected to a voltage amplifier, one end of the voltage amplifier is connected to a signal demodulation module, one end of the signal demodulation module is connected to a signal decoding module, one end of the ambient light sensor is connected to a microcontroller, a level conversion circuit is connected between the ambient light sensor and the microcontroller, one end of the microcontroller is connected to a digital-to-analog converter, and one end of the digital-to-analog converter is connected to the voltage amplifier.

[0031] The ambient light sensor is sensor U4, which is powered by a voltage regulator U5 at 1.8V. The VDD pin of sensor U4 is connected to the OUT pin of voltage regulator U5. The SDA pin of sensor U4 is pulled up to 1.8V by resistor R63. The VSS pin of sensor U4 is grounded. The GPIO2 pin of sensor U4 is connected to a grounded resistor R65. The GPIO1 pin of sensor U4 is pulled up to 1.8V by resistor R66. The SCL pin of sensor U4 is pulled up to 1.8V by resistor R64.

[0032] The voltage regulator U5, in conjunction with the external circuitry, converts 5V to the 1.8V required by the sensor U4. The GND pin of the voltage regulator U5 is grounded, and the IN pin of the voltage regulator U5 is connected to the 5V voltage. The IN pin of the voltage regulator U5 is connected to capacitors C67 and C68 in parallel, with the other ends of capacitors C67 and C68 grounded. The OUT pin of the voltage regulator U5 outputs 1.8V. The OUT pin of the voltage regulator U5 is also connected to capacitors C69 and C70 in parallel, with the other ends of capacitors C69 and C70 grounded.

[0033] exist Figure 3 In this circuit, the system power supply provides 5V, which is converted to the 1.8V required by sensor U4 using voltage regulator U5 and external circuitry. Capacitors C67 and C68 are filter capacitors for the 5V power supply, while capacitors C69 and C70 are filter capacitors for the 1.8V power supply. The SDA bus of sensor U4 is pulled up to 1.8V using resistor R63, the SCL bus of sensor U4 is pulled up to 1.8V using resistor R64, and the INT (interrupt) signal of sensor U4 is pulled up to 1.8V using resistor R66. The GPIO2 pin of sensor U4 is pulled down to ground using resistor R65.

[0034] The microcontroller's I / O interface is connected to a tri-color LED indicator, which includes a red LED D1, a green LED D2, and a blue LED D3. A resistor R70 is connected between the red LED D1 and pin 1 of the microcontroller, a resistor R71 is connected between the green LED D2 and pin 2 of the microcontroller, and a resistor R72 is connected between the blue LED D3 and pin 3 of the microcontroller. A resistor R67 is connected to the microcontroller's SDA bus, a resistor R68 is connected to the microcontroller's SCL bus, and a resistor R69 is connected to the microcontroller's INT input terminal. The other ends of resistors R67, R68, and R69 are all connected to a 3V voltage.

[0035] Figure 4 In the diagram, the ST capacitor C15W4K40S4 is a microcontroller model. The minimum system components required for its normal operation are omitted; only the connections relevant to this invention are shown. The microcontroller's SCL and SDA buses are pulled up to the microcontroller's 3V supply voltage using resistors R68 and R67, respectively. The INT signal from sensor U4 is pulled up to 3V using resistor R69. Red LED D1, green LED D2, and blue LED D3 are integrated red, green, and blue tri-color LED indicator lights. When the red light is needed, the microcontroller outputs a high level on the I / O pin connected to red LED D1 and a low level on the I / O pins connected to green and blue LEDs D3. Resistors R70, R71, and R72 are current-limiting resistors.

[0036] The voltage amplifier includes an amplifier U6 and an inductor L1 connected to an external 5V power supply. One end of the inductor L1 is connected to capacitors C22 and C33, C32 and C34, and C38 and C39 connected in parallel. The terminals of capacitors C22 and C33 are connected to the VPOS pin of the amplifier U6, the terminals of capacitors C32 and C34 are connected to the VPSO pin of the amplifier U6, and the terminals of capacitors C38 and C39 are connected to the VPSI pin of the amplifier U6.

[0037] Figure 2The voltage amplifier in the system has adjustable gain. First, set its gain to 0dB (no amplification). In a dark room, place the visible light receiver in a location with strong illumination from the transmitter and find the maximum illuminance value Emax for communication between the two ends. Then, set the voltage amplifier gain to its maximum value and place the visible light receiver in a location with weak illumination from the transmitter to find the minimum illuminance value Emin for communication between the two ends. The illuminance value between Emin and Emax represents the illuminance range within which the system can communicate. A microcontroller and red, green, and blue LEDs can be used to indicate the illuminance status at the receiver. When the illuminance exceeds Emax, a red light illuminates, indicating excessive illuminance; when the illuminance is below Emin, a blue light illuminates, indicating insufficient illuminance; when the illuminance is between Emin and Emax, a green light illuminates, indicating normal illuminance.

[0038] The adjustable-gain voltage amplifier, taking the AD8330 as an example, has a total gain of 50dB. The illuminance values ​​between Emin and Emax can be divided into 25 segments, from smallest to largest: E1 to E25. The gain for segment E25 is 2dB, and the gain for segment E1 is the maximum value of 50dB. The gain interval between each two segments is 2dB. The voltage at pin 7 (VDBS) of the AD8330 controls the gain; every 30mV corresponds to 1dB of gain, and every 60mV corresponds to 2dB of gain.

[0039] Figure 6 In this circuit, amplifier U6 requires three power supplies: VPOS, VPSO, and VPSI. The 5V supplied by the system power supply is filtered through inductor L1 and capacitors C22 and C33 to power VPOS, through inductor L1 and capacitors C32 and C34 to power VPSO, and through inductor L1 and capacitors C38 and C39 to power VPSI. Capacitor C36 and resistor R26 constitute an amplification offset compensation circuit. Resistor R38 is used to pull the voltage at pin 6 (MODE) of amplifier U6 up to 5V, so that the amplification factor of amplifier U6 increases with the increase of the voltage at pin 7 (VDBS). The differential signals IN+ and IN- from the preamplifier are input to pins 4 and 5 of amplifier U6 as the signals to be amplified. The amplified signals are output from pins 13 and 12, filtered by a low-pass circuit composed of capacitors C27, C28, C40, C41, and resistor R27, and then sent to the OFDM demodulation module.

[0040] A capacitor C36 and a resistor R26 are connected in series between the OFST pin and the CNTR pin of the amplifier U6. A resistor R35 is connected to the VDBS pin of the amplifier U6. A resistor R38 is connected between the VPSI pin and the MODE pin of the amplifier U6. A capacitor C27 and a resistor R27 are connected in parallel between the OPLO pin and the OPHI pin of the amplifier U6. A capacitor C40 is connected between one end of the capacitor C27 and one end of the resistor R27. A capacitor C41 is connected between the other end of the capacitor C27 and the other end of the resistor R27.

[0041] The digital-to-analog converter (DAC) communicates with the microcontroller via an I2C bus. The DAC is converter U2, and its 3V power supply comes from a voltage regulator U3. The GND pin of voltage regulator U3 is grounded, and a 5V voltage is connected to its IN pin. Capacitors C64 and C63 are also connected in parallel to the IN pin of voltage regulator U3. The other ends of capacitors C64 and C63 are both grounded. The OUT pin of voltage regulator U3 outputs 3V.

[0042] The GND pin of converter U2 is grounded. A resistor R62 is connected to the SDA pin of converter U2. A resistor R61 is connected to the SCL pin of converter U2. The terminals of resistors R61 and R62 output a 3V voltage. A capacitor C71 is connected to the VOUT pin of converter U2. The other end of capacitor C71 is grounded. The A0 pin of converter U2 is grounded. The VDD pin of converter U2 is the power supply pin. A capacitor C61 and a capacitor C62 are connected in parallel to the VDD pin. The other ends of capacitors C61 and C62 are both grounded.

[0043] When the microcontroller reads the illuminance data from the ambient light sensor and corrects it, it outputs the digital gain value of a voltage amplifier corresponding to the illuminance range to the AD5311. The AD5311 then outputs an analog value to the AD8330, so that the current amplification gain of the AD8330 is the desired value.

[0044] exist Figure 7 In this circuit, the system power supply provides 5V, which is converted to the 3V required by converter U2 using voltage regulator U3 and external circuitry. Capacitors C63 and C64 are filter capacitors for the 5V power supply, while capacitors C61 and C62 are filter capacitors for the 3V power supply. The SDA bus of converter U2 is pulled up to 3V using resistor R62, and the SCL bus of converter U2 is pulled up to 3V using resistor R61. Pin 4 of converter U2 is the analog output pin of the digital-to-analog converter, and is filtered by capacitor C71.

[0045] For example, if the AD8330 requires a gain of 10dB, then the voltage at pin 7 needs to be 0.3V. In the AD5311, 0.3V corresponds to the digital value 102. The microcontroller sends the binary number 01100110 to the register of the AD5311 via the I2C bus, converts the digital-to-analog conversion to 0.3V, and sends it to the AD8330.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A visible light communication system, characterized in that, include: Signal transmitting module and signal receiving module; The signal transmission module includes an OFDM signal amplification circuit, which comprises a chip U1, a variable resistor RP1, and a resistor R2. A resistor R9 is connected to the IN- pin of the chip U1, and a capacitor C6 is connected to one end of the resistor R9. The other end of the capacitor C6 is grounded. The variable resistor RP1 is connected between the IN- and OUT pins of the chip U1. Resistors R2, R5, and R3 are connected to the IN+ pin of the chip U1, respectively. A capacitor C1 is connected in series to one end of the resistor R3, and one end of the capacitor C1 is connected to the OFDM signal. One end of the resistor R2 is connected to the OFDM signal, and the other end is grounded. A capacitor C7 and a capacitor C8 are connected in parallel to the +Vs pin of the chip U1, and the other ends of the capacitors C7 and C8 are grounded. A capacitor C4 is connected to the OUT pin of the chip U1, and one end of the capacitor C4 is connected to the resistor R6. The amplified OFDM signal is output from the rear end of the resistor R6. The signal receiving module includes a photoelectric sensor and an ambient light sensor. One end of the photoelectric sensor is connected to a transimpedance amplifier, one end of the transimpedance amplifier is connected to a voltage amplifier, one end of the voltage amplifier is connected to a signal demodulation module, one end of the signal demodulation module is connected to a signal decoding module, one end of the ambient light sensor is connected to a microcontroller, a level conversion circuit is connected between the ambient light sensor and the microcontroller, one end of the microcontroller is connected to a digital-to-analog converter, and the other end of the digital-to-analog converter is connected to the voltage amplifier.

2. The visible light communication system according to claim 1, characterized in that: The ambient light sensor has I 2 The ambient light sensor detects illuminance data via communication interfaces SCL and SDA. 2 The C communication interface is read out and used to work with the microcontroller.

3. A visible light communication system according to claim 2, characterized in that: The ambient light sensor is sensor U4, which is powered by a voltage regulator U5 at 1.8V. The VDD pin of sensor U4 is connected to the OUT pin of voltage regulator U5. The SDA pin of sensor U4 is pulled up to 1.8V by resistor R63. The VSS pin of sensor U4 is grounded. The GPIO2 pin of sensor U4 is connected to a grounded resistor R65. The GPIO1 pin of sensor U4 is pulled up to 1.8V by resistor R66. The SCL pin of sensor U4 is pulled up to 1.8V by resistor R64. The voltage regulator U5, in conjunction with the external circuitry, converts 5V to the 1.8V required by the sensor U4. The GND pin of the voltage regulator U5 is grounded, and the IN pin of the voltage regulator U5 is connected to the 5V voltage. The IN pin of the voltage regulator U5 is connected to capacitors C67 and C68 in parallel, with the other ends of capacitors C67 and C68 grounded. The OUT pin of the voltage regulator U5 outputs 1.8V. The OUT pin of the voltage regulator U5 is also connected to capacitors C69 and C70 in parallel, with the other ends of capacitors C69 and C70 grounded.

4. A visible light communication system according to claim 1, characterized in that: The microcontroller's I / O interface is connected to a tri-color LED indicator, which includes a red LED D1, a green LED D2, and a blue LED D3. A resistor R70 is connected between the red LED D1 and pin 1 of the microcontroller, a resistor R71 is connected between the green LED D2 and pin 2 of the microcontroller, and a resistor R72 is connected between the blue LED D3 and pin 3 of the microcontroller. A resistor R67 is connected to the microcontroller's SDA bus, a resistor R68 is connected to the microcontroller's SCL bus, and a resistor R69 is connected to the microcontroller's INT input terminal. The other ends of resistors R67, R68, and R69 are all connected to a 3V voltage.

5. A visible light communication system according to claim 1, characterized in that: The voltage amplifier includes an amplifier U6 and an inductor L1 connected to an external 5V power supply. One end of the inductor L1 is connected to capacitors C22 and C33, C32 and C34, and C38 and C39 connected in parallel. The terminals of capacitors C22 and C33 are connected to the VPOS pin of the amplifier U6, the terminals of capacitors C32 and C34 are connected to the VPSO pin of the amplifier U6, and the terminals of capacitors C38 and C39 are connected to the VPSI pin of the amplifier U6.

6. A visible light communication system according to claim 5, characterized in that: A capacitor C36 and a resistor R26 are connected in series between the OFST pin and the CNTR pin of amplifier U6. A resistor R35 is connected to the VDBS pin of amplifier U6. A resistor R38 is connected between the VPSI pin and the MODE pin of amplifier U6. A capacitor C28 and a capacitor C41 are connected in parallel to the OPLO pin of amplifier U6. The other end of capacitor C28 is grounded, and the other end of capacitor C41 is connected to a resistor R27. A capacitor C27 and a capacitor C40 are connected in parallel to the OPHI pin of amplifier U6. The other end of capacitor C27 is grounded, and the other end of capacitor C40 is connected to a resistor R27.

7. A visible light communication system according to claim 1, characterized in that: The digital-to-analog converter and the microcontroller are connected via 1 2 C-bus communication, the digital-to-analog converter is converter U2, the 3V power supply of converter U2 comes from voltage regulator U3, the GND pin of voltage regulator U3 is grounded, the IN pin of voltage regulator U3 is connected to a 5V voltage, and capacitors C64 and C63 are also connected in parallel to the IN pin of voltage regulator U3. The other end of capacitor C64 and the other end of capacitor C63 are both grounded, and the OUT pin of voltage regulator U3 outputs 3V.

8. A visible light communication system according to claim 7, characterized in that: The GND pin of converter U2 is grounded. A resistor R62 is connected to the SDA pin of converter U2. A resistor R61 is connected to the SCL pin of converter U2. Resistors R61 and R62 are connected to a 3V power supply. A capacitor C71 is connected to the VOUT pin of converter U2. The other end of capacitor C71 is grounded. The A0 pin of converter U2 is grounded. The VDD pin of converter U2 is connected to a 3V power supply. A capacitor C61 and a capacitor C62 are connected in parallel to the VDD pin. The other ends of capacitors C61 and C62 are both grounded.

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