An adaptive piezoresistive pulse signal acquisition circuit

Abstract

The application discloses a self-adaptive piezoresistive pulse signal acquisition circuit and belongs to the technical field of biomedical signal detection. The circuit comprises an analog-digital conversion chip and a microcontroller. At least one of the analog input channels of the analog-digital conversion chip is configured as a constant current source output channel, is used for connecting one end of a piezoresistive sensor, and at least two other channels are configured as pseudo differential voltage input channels and are respectively used for connecting two ends of the sensor. The microcontroller is connected with the analog-digital conversion chip, the internal storage of the microcontroller has a self-adaptive configuration program, the sensor resistance value is acquired according to initial measurement, the voltage value under different constant current values is predicted, the candidate combination is screened in combination with the full-scale voltage corresponding to the gain, the optimal configuration is determined according to the voltage utilization rate, and the pulse signal is acquired. The application can automatically adapt to piezoresistive sensors with a wide resistance value range, does not need manual adjustment, improves the precision and universality of signal acquisition and reduces system power consumption.

Description

Technical Field

[0001] This invention belongs to the field of biomedical signal detection technology, and in particular relates to an adaptive piezoresistive pulse signal acquisition circuit. Background Technology

[0002] Pulse signal is one of the important physiological parameters of the human body. Piezoresistive sensors are widely used in wearable pulse detection devices due to their high sensitivity, fast response, and simple structure. However, the substrate resistance of different types of piezoresistive materials varies greatly (from tens of ohms to tens of kiloohms). Existing circuits are usually designed for a specific resistance range. When the sensor is changed or the material batch changes, it is often necessary to manually adjust the excitation current or amplify the gain, or even replace the hardware, which is inconvenient to use and difficult to achieve universality.

[0003] Existing technologies also employ solutions that achieve partial matching using multi-level current sources or programmable gain amplifiers (PGAs). However, most of these require users to manually set the parameters based on the sensor's nominal values ​​or use fixed configurations. They cannot automatically identify sensor characteristics and complete optimal parameter configuration at the moment of connection, resulting in unstable signal-to-noise ratios and low dynamic range utilization. Furthermore, traditional solutions often use external constant current source circuits, increasing system complexity and power consumption, which is detrimental to the miniaturization and low-power design of wearable devices.

[0004] Because existing piezoresistive pulse signal acquisition circuits cannot automatically adapt to sensors with a wide range of resistance values, they require manual configuration, are inconvenient to use, and have unstable signal quality. This is a problem that still needs to be solved. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides an adaptive piezoresistive pulse signal acquisition circuit, comprising: An analog-to-digital converter chip has multiple analog input channels, wherein at least one analog input channel is configured as a constant current source output channel for connecting to one end of a piezoresistive sensor, and at least two other analog input channels are configured as pseudo-differential voltage input channels for connecting to the two ends of the piezoresistive sensor, respectively, to measure the voltage across the piezoresistive sensor. A microcontroller, connected to the analog-to-digital converter chip, is used to configure the analog-to-digital converter chip and read the conversion result; The microcontroller stores an adaptive configuration program, which is configured to perform the following steps: The resistance value of the piezoresistive sensor is obtained based on the voltage across the piezoresistive sensor measured by the first constant current value and the first gain. Based on the resistance value, the predicted voltage values ​​corresponding to the two ends of the piezoresistive sensor under multiple candidate constant current values ​​are obtained. Based on the comparison results between each predicted voltage value and the full-scale voltage corresponding to multiple candidate gains, candidate combinations in which the predicted voltage value does not exceed the full-scale voltage are selected. The target combination is determined from the selected candidate combinations based on the ratio of the predicted voltage value to the full-scale voltage in each candidate combination. The analog-to-digital converter chip is configured with the constant current value and gain in the target combination to acquire pulse signals.

[0006] Optionally, the adaptive configuration procedure is configured to perform the step of obtaining the resistance value of the piezoresistive sensor based on the voltage across the piezoresistive sensor measured with a first constant current value and a first gain, specifically including: The analog-to-digital converter chip is controlled to measure the piezoresistive sensor with the first constant current value and the first gain to obtain the voltage across the piezoresistive sensor; The resistance value of the piezoresistive sensor is calculated based on the voltage across the piezoresistive sensor and the first constant current value.

[0007] Optionally, the adaptive configuration procedure is configured to perform the step of obtaining the predicted voltage value across the piezoresistive sensor under multiple candidate constant current values ​​based on the resistance value, specifically including: Obtain multiple candidate constant current values; Each candidate constant current value is multiplied by the resistance value to obtain the predicted voltage value corresponding to each candidate constant current value.

[0008] Optionally, the adaptive configuration procedure is configured to perform a step of selecting candidate combinations in which the predicted voltage values ​​do not exceed the full-scale voltage based on a comparison between each predicted voltage value and the full-scale voltage corresponding to a plurality of candidate gains, specifically including: Obtain multiple candidate gains and the full-scale voltage corresponding to each candidate gain; Compare each of the predicted voltage values ​​with the full-scale voltage corresponding to each of the candidate gains; When the predicted voltage value is less than or equal to the full-scale voltage, the combination of the current candidate constant current value and the candidate gain is determined as the candidate combination.

[0009] Optionally, the adaptive configuration procedure is configured to perform the step of determining a target combination from the selected candidate combinations based on the ratio of the predicted voltage value to the full-scale voltage in each candidate combination, specifically including: For each of the candidate combinations, calculate the ratio of the predicted voltage value to the full-scale voltage; Candidate combinations whose ratios fall within a preset preferred range are retained; The target combination is determined from the retained candidate combinations based on the preset priority.

[0010] Optionally, the adaptive configuration procedure is configured to perform the step of determining a target combination from the reserved candidate combinations according to a preset priority, specifically including: Among the remaining candidate combinations, the combination with the largest gain is selected in descending order of gain. When the gain is the same, select the combination with the smaller constant current value in ascending order of constant current value to determine the target combination.

[0011] Optionally, the pseudo-differential voltage input channel includes a positive input terminal and a negative input terminal. The positive input terminal is used to connect to one end of the piezoresistive sensor connected to the constant current source output channel, and the negative input terminal is used to connect to one end of the piezoresistive sensor connected to analog ground.

[0012] Optionally, the microcontroller is connected to the analog-to-digital converter chip via a serial peripheral interface, and is used to configure the registers of the analog-to-digital converter chip and read the conversion results of the analog-to-digital converter chip.

[0013] Optionally, the microcontroller is also used to detect the signal state during the acquisition of pulse signals, and when signal saturation or signal strength is detected to be lower than a preset threshold, the adaptive configuration program is re-executed.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: High versatility: The same circuit board can be adapted to various piezoresistive pulse sensors with resistance values ​​ranging from tens of ohms to tens of kilohms, without the need to replace hardware or manually adjust. High measurement accuracy: By dynamically matching the excitation current and PGA gain, the signal is always kept within the optimal input range of the ADC. Combined with the high resolution (24-bit) and low noise characteristics of the AD7124, a pulse waveform with a high signal-to-noise ratio can be obtained. Low power design: By selecting the STM32L4 series ultra-low power MCU, ADP1607 high-efficiency power management chip and low power Bluetooth module, combined with the optional power priority configuration strategy in the adaptive algorithm, it is expected to extend the battery life of wearable devices. Easy to use: The device automatically completes sensor identification and parameter configuration after power-on, enabling "plug and test". Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1This is a circuit system block diagram according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the overall workflow of piezoresistive pulse signal acquisition according to an embodiment of the present invention.

[0016] Figure 3 This is a flowchart of the adaptive configuration algorithm according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the pin connections of the STM32L432KCU6 microcontroller chip according to an embodiment of the present invention. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0019] Example 1 This embodiment provides an adaptive piezoresistive pulse signal acquisition circuit, including: An analog-to-digital converter chip has multiple analog input channels, wherein at least one analog input channel is configured as a constant current source output channel for connecting to one end of a piezoresistive sensor, and at least two other analog input channels are configured as pseudo-differential voltage input channels for connecting to the two ends of the piezoresistive sensor, respectively, to measure the voltage across the piezoresistive sensor. A microcontroller, connected to the analog-to-digital converter chip, is used to configure the analog-to-digital converter chip and read the conversion result; The microcontroller stores an adaptive configuration program, which is configured to perform the following steps: The resistance value of the piezoresistive sensor is obtained based on the voltage across the piezoresistive sensor measured by the first constant current value and the first gain. Based on the resistance value, the predicted voltage values ​​corresponding to the two ends of the piezoresistive sensor under multiple candidate constant current values ​​are obtained. Based on the comparison results between each predicted voltage value and the full-scale voltage corresponding to multiple candidate gains, candidate combinations in which the predicted voltage value does not exceed the full-scale voltage are selected. The target combination is determined from the selected candidate combinations based on the ratio of the predicted voltage value to the full-scale voltage in each candidate combination. The analog-to-digital converter chip is configured with the constant current value and gain in the target combination to acquire pulse signals.

[0020] The pseudo-differential voltage input channel includes a positive input terminal and a negative input terminal. The positive input terminal is used to connect to one end of the piezoresistive sensor connected to the constant current source output channel, and the negative input terminal is used to connect to one end of the piezoresistive sensor connected to analog ground.

[0021] The microcontroller is connected to the analog-to-digital converter chip via a serial peripheral interface and is used to configure the registers of the analog-to-digital converter chip and read the conversion results of the analog-to-digital converter chip.

[0022] The following is combined with Figure 1 A detailed description of the data acquisition circuit is provided below: See Figure 1 This figure is a circuit system block diagram of an embodiment of the present invention. The figure exemplarily illustrates the interconnection structure of the microcontroller STM32L432KCU6, the analog-to-digital converter chip AD7124, the power management module ADP1607, and the Bluetooth module E104-BT5005A, providing a hardware foundation for the subsequent detailed explanation of the adaptive signal acquisition method.

[0023] Reference Figure 1 The STM32L432KCU6 microcontroller connects to the AD7124 analog-to-digital converter chip via the SPI interface to control its working mode and read the conversion results.

[0024] Reference Figure 1 The AD7124's analog input pin AIN0 is configured as a constant current source output and connected to one end of the piezoresistive sensor material interface. The other end of the piezoresistive sensor material interface is connected to AGND on the circuit board. AIN2 and AIN3 are configured as pseudo-differential voltage input pairs and connected to the two ends of the sensor, respectively.

[0025] Reference Figure 1 The power management module uses two ADP1607 chips to convert the battery voltage into a stable 3.3V, one analog voltage and one digital voltage, to power each chip.

[0026] Reference Figure 1 The Bluetooth module E104-BT5005A connects to the MCU via USART and sends the collected pulse data to a mobile phone or host computer.

[0027] Figure 4This document details the pin connections for the STM32L432KCU6 microcontroller chip. First, the program download circuit is connected, with the program reset button connected via the NRST pin. PA13 connects to STLINK's SWDIO, PA14 to STLINK's SWCLK, DGND to STLINK's GND, and NRST to STLINK's NRST. The internal clock crystal oscillator PC14-OSC32_IN and PC15-OSC32_OUT of the SYM32 chip are used for grounding. PA0 connects to the Bluetooth WKP (p0.05) pin for Bluetooth wake-up and data transmission. PA1 connects to the AD7124's SYNC pin to enable the ADC. PA2 connects to the positive terminal of the power supply battery for monitoring battery level. PA3 connects to the AD7124's DOUT / RDY multiplexed pin as the data ready signal. PA4, PA5, PA6, and PA7 are for SPI communication, connected to the AD7124's CS, SCLK, DOUT / RDY, and DIN pins respectively. PB0 is connected to the Bluetooth MOD (P0.04) pin for Bluetooth configuration. PA9 and PA10 are connected to the Bluetooth RXD (P0.20) and TXD (P0.14) pins respectively for data transmission. PA9 and PA10 are also connected to an external USART for outputting debug information. The PH3 / BOOT0 pin is connected to DGND to ensure normal chip operation.

[0028] Figure 2 This is a system workflow diagram provided for an embodiment of the present invention. The flowchart illustrates the complete working process of the device from power-on startup to completion of pulse signal acquisition and transmission, specifically including the following steps: First, after the device powers on, the microcontroller executes an adaptive configuration algorithm. This algorithm includes the following sub-steps: initializing the AD7124, setting up its SPI communication with the microcontroller, and performing internal calibration; configuring the initial constant current source to a 50 µA setting and the initial PGA gain to 1 (corresponding to a maximum input range of 2.5 V); acquiring the initial voltage V_x across the piezoresistive sensor via the AIN2 / AIN3 channels, and calculating the sensor's current resistance value according to the formula R_x = V_x / 50 µA; based on this resistance value, iterating through all available constant current source settings and PGA gain combinations, and selecting the optimal configuration that satisfies the voltage utilization rate K ∈ [0.3, 0.8]; finally, configuring the AD7124 to this optimal combination.

[0029] Subsequently, the microcontroller configures the Bluetooth module via the USART interface, enabling it to connect and preparing for wireless data transmission with the host computer. After completing the above initialization configuration, the system enters the normal data acquisition cycle: Start collecting pulse signals: The microcontroller controls the AD7124 to continuously collect the voltage signals across the sensor according to the configured optimal parameters; SPI data transmission to MCU: The AD7124 transmits the acquired digital signals to the microcontroller in real time via the SPI interface; Data processing: The microcontroller performs digital filtering and feature extraction on the received pulse wave data, and calculates key physiological parameters such as blood pressure and heart rate; Sending data to the host computer via Bluetooth: The microcontroller packages the processed data and sends it to a mobile app or cloud server via the Bluetooth module.

[0030] After data collection is complete, the system determines whether to continue collecting data: If the user chooses to continue collecting data, the process returns to the "Start collecting pulse signals" step and uses the currently configured parameters for the next round of data collection. If the user chooses to stop data collection, the system will enter a low-power standby mode or terminate the workflow directly.

[0031] In a preferred embodiment, the system can add a signal anomaly detection function after the data processing step. Specifically, the microcontroller detects the signal status during the acquisition of pulse signals. When signal saturation or signal strength below a preset threshold is detected, it indicates that the current configuration may no longer be applicable (e.g., the sensor has been replaced or drifted), and the adaptive configuration program is re-executed to re-optimize the parameters.

[0032] Furthermore, the adaptive configuration procedure is configured to perform the step of obtaining the resistance value of the piezoresistive sensor based on the voltage across the piezoresistive sensor measured with a first constant current value and a first gain, specifically including: The analog-to-digital converter chip is controlled to measure the piezoresistive sensor with the first constant current value and the first gain to obtain the voltage across the piezoresistive sensor; The resistance value of the piezoresistive sensor is calculated based on the voltage across the piezoresistive sensor and the first constant current value.

[0033] Furthermore, the adaptive configuration procedure is configured to perform the step of obtaining the predicted voltage value across the piezoresistive sensor under multiple candidate constant current values ​​based on the resistance value, specifically including: Obtain multiple candidate constant current values; Each candidate constant current value is multiplied by the resistance value to obtain the predicted voltage value corresponding to each candidate constant current value.

[0034] Furthermore, the adaptive configuration procedure is configured to perform a step of selecting candidate combinations in which the predicted voltage values ​​do not exceed the full-scale voltage, based on a comparison between each predicted voltage value and the full-scale voltage corresponding to a plurality of candidate gains. Specifically, this includes: Obtain multiple candidate gains and the full-scale voltage corresponding to each candidate gain; Compare each of the predicted voltage values ​​with the full-scale voltage corresponding to each of the candidate gains; When the predicted voltage value is less than or equal to the full-scale voltage, the combination of the current candidate constant current value and the candidate gain is determined as the candidate combination.

[0035] Furthermore, the adaptive configuration procedure is configured to perform the step of determining a target combination from the selected candidate combinations based on the ratio of the predicted voltage value to the full-scale voltage in each candidate combination, specifically including: For each of the candidate combinations, calculate the ratio of the predicted voltage value to the full-scale voltage; Candidate combinations whose ratios fall within a preset preferred range are retained; The target combination is determined from the retained candidate combinations based on the preset priority.

[0036] Furthermore, the adaptive configuration procedure is configured to perform the step of determining the target combination from the reserved candidate combinations according to a preset priority, specifically including: Among the remaining candidate combinations, the combination with the largest gain is selected in descending order of gain. When the gain is the same, select the combination with the smaller constant current value in ascending order of constant current value to determine the target combination.

[0037] Now combined Figure 3 A detailed explanation follows. This flowchart illustrates how the microcontroller automatically determines the optimal excitation current and PGA gain based on initial measurement results, specifically including the following steps: Step S301: Begin; After the device is powered on, the microcontroller initiates the adaptive configuration process.

[0038] Step S302: Initialize AD7124; The microcontroller configures the AD7124 via the SPI interface, sets the initial constant current source to 50 µA, the initial PGA gain to 1 (corresponding to full scale 2.5 V), and performs internal calibration to ensure measurement accuracy.

[0039] Step S303: Measure the voltage value V_x across the sensor; The initial voltage V_x across the piezoresistive sensor is acquired through the pseudo-differential input channels AIN2 / AIN3 of the AD7124.

[0040] Step S304: Calculate the sensor resistance R_x; According to Ohm's law, the current resistance of the sensor is calculated as: R_x = V_x / 50 µA Step S305: Calculate the voltage value V_i generated across the sensor at different current levels based on R_x; For the seven programmable constant current source levels supported by AD7124 (0.1 µA, 50 µA, 100 µA, 250 µA, 500 µA, 750 µA, 1 mA), calculate the corresponding predicted voltage: V_i = I_i × R_x; Step S306: Determine whether V_i is less than or equal to the full-scale voltage PGA_j corresponding to the current PGA gain; Each V_i is compared with the full-scale voltage corresponding to the eight PGA gains (1, 2, 4, 8, 16, 32, 64, 128). If V_i ≤ PGA_j, proceed to step S207; otherwise, discard the combination and end the process.

[0041] Step S307: Calculate the voltage utilization rate K = V_i / PGA_j; For the selected combinations, the K value is calculated to evaluate the proportion of the signal in the ADC range.

[0042] Step S308: Determine whether K is within the preset preferred range (0.3). <K<0.8); If the K value is between 0.3 and 0.8, the combination is retained; otherwise, the combination is discarded and the process ends.

[0043] Step S309: Select the optimal combination from the reserved combinations as the final configuration according to the preset priority; Among the retained combinations, the optimal combination is selected according to the priority order of PGA gain from small to large (the larger the gain, the lower the noise) and constant current value from small to large (the smaller the current, the lower the power consumption).

[0044] Step S310: Configure AD7124 to the optimal constant current value and PGA gain, and start acquiring signals; The microcontroller writes the selected current level and PGA gain into the AD7124 register to start the formal pulse signal acquisition.

[0045] Step S311: End.

[0046] After the adaptive configuration process is completed, the system enters the regular data acquisition cycle.

[0047] To more clearly illustrate the above algorithm flow, the following example uses a 1.5 kΩ piezoresistive sensor to demonstrate the calculation and selection process for each step in detail: Step S303: V_x was measured to be 75 mV; Step S304: Calculate \(R_x = 75\ mV / 50\ \mu A = 1.5\ k\Omega\); Step S305: Calculate the predicted voltage \(V_i\) at each current range; \(I = 50\ \mu A\rightarrow V = 75\ mV\); \(I = 100\ \mu A\rightarrow V = 150\ mV\); \(I = 250\ \mu A\rightarrow V = 375\ mV\); \(I = 500\ \mu A\rightarrow V = 750\ mV\); \(I = 750\ \mu A\rightarrow V = 1.125\ V\); \(I = 1\ mA\rightarrow V = 1.5\ V\); (The voltage generated by the \(0.1\ \mu A\) range, \(0.15\ mV\), is too small and is ignored); Step S306: Compare each \(V_i\) with the full-scale voltage corresponding to the PGA gain (see Table 1), and select the combinations where \(V_i\leq PGA_j\).

[0048] Steps S307 - S308: Calculate the \(K\) value for each retained combination, and select the combinations where \(0.3 < K < 0.8\): For the \(50\ \mu A\) range (\(V = 75\ mV\)): \(PGA = 1(2500\ mV)\): \(K = 75 / 2500 = 0.03\rightarrow\) Rejected (\(< 0.3\)); \(PGA = 2(1250\ mV)\): \(K = 75 / 1250 = 0.06\rightarrow\) Rejected; \(PGA = 4(625\ mV)\): \(K = 75 / 625 = 0.12\rightarrow\) Rejected; \(PGA = 8(312.5\ mV)\): \(K = 75 / 312.5 = 0.24\rightarrow\) Rejected; \(PGA = 16(156.25\ mV)\): \(K = 75 / 156.25 = 0.48\rightarrow\) Retained; \(PGA = 32(78.125\ mV)\): \(K = 75 / 78.125 = 0.96\rightarrow\) Rejected; \(PGA = 64(39.0625\ mV)\): \(K = 75 / 39.0625 = 1.92\rightarrow\) Rejected; \(PGA = 128(19.53125\ mV)\): \(V_i>V_{PGA_j}\), Rejected; For the \(250\ \mu A\) range (\(V = 375\ mV\)): \(PGA = 1(2500)\): \(K = 0.15\rightarrow\) Rejected; \(PGA = 2(1250)\): \(K = 0.3\rightarrow\) Retained (the boundary value can be retained); PGA=4 (625): K=0.6 → Retain; PGA=8 (312.5): Vi > full scale → obsolete; Higher gains all have V_i > full scale; ⇒ Retain the following combinations: (250 µA, PGA=2), (250 µA, PGA=4); 500 µA range (V=750 mV): PGA=1 (2500): K=0.3 → Reserved; PGA=2 (1250): K=0.6 → Retain; PGA=4 (625): V_i > full scale → obsolete; Higher gains all have V_i > full scale; ⇒ Retain the following combinations: (500 µA, PGA=1), (500 µA, PGA=2); 750 µA range (V=1125 mV): PGA=1 (2500): K=0.45 → Reserved; PGA=2 (1250): K=0.9 → Eliminate; PGA=4 (625): V_i > full scale → obsolete; ⇒ Retained combination: (750 µA, PGA=1); 1 mA setting (V=1500 mV): PGA=1 (2500): K=0.6 → Reserved; PGA=2 (1250): Vi > full scale → obsolete; ⇒ Retain combination: (1 mA, PGA=1); Step S309: The remaining combinations are summarized as follows: Current PGA K value; 50 µA 16 0.48; 100 µA 8 0.48; 250 µA 2 0.3; 250 µA 4 0.6; 500 µA 1 0.3; 500 µA 2 0.6; 750 µA 1 0.45; 1 mA 1 0.6; Based on preset optimization rules, and considering both signal quality and power consumption, the optimal configuration is selected from the reserved combinations. In this embodiment, a PGA gain combination with a good match between the input range and the pulse signal amplitude, and superior noise performance, is preferred. Within the same PGA gain level, combinations with lower current are preferred to reduce power consumption. Therefore, the optimal combination is configured as 100µA, with PGA=8.

[0049] Step S310: Configure the AD7124 to the selected optimal combination (e.g., 500 µA constant current source, PGA=1) and begin formally acquiring pulse signals.

[0050] The present invention has the following beneficial effects: This invention utilizes an adaptive configuration program embedded in a microcontroller to automatically identify the resistance value of a piezoresistive pulse sensor upon connection. Based on a comparison of the predicted voltage and the full-scale voltage, as well as calculations of voltage utilization, it dynamically matches the optimal constant current source setting and PGA gain combination. This enables adaptive matching of piezoresistive sensors across a wide resistance range, from tens of ohms to tens of kiloohms. Users do not need to manually adjust the excitation current or amplify the gain for different sensors, nor do they need to replace hardware, achieving convenient plug-and-play operation.

[0051] Based on this, since the adaptive configuration program can ensure that the signal is always within the optimal input range of the analog-to-digital converter, combined with the low noise characteristics of the high-resolution analog-to-digital converter chip, the signal-to-noise ratio and measurement accuracy of the pulse signal are effectively improved, avoiding the problem of reduced signal-to-noise ratio due to excessively small signal amplitude or nonlinear distortion caused by the signal exceeding the full scale.

[0052] In addition, this invention uses an ultra-low power microcontroller and a high-efficiency power management chip, combined with a power optimization strategy that prioritizes smaller constant current values ​​in the adaptive algorithm. This reduces the overall power consumption of the system while ensuring signal quality, which helps to extend the battery life of wearable devices and meet the application requirements of miniaturization and low power consumption for wearable medical devices.

[0053] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An adaptive piezoresistive pulse signal acquisition circuit, characterized in that, include: An analog-to-digital converter chip has multiple analog input channels, wherein at least one analog input channel is configured as a constant current source output channel for connecting to one end of a piezoresistive sensor, and at least two other analog input channels are configured as pseudo-differential voltage input channels for connecting to the two ends of the piezoresistive sensor, respectively, to measure the voltage across the piezoresistive sensor. A microcontroller, connected to the analog-to-digital converter chip, is used to configure the analog-to-digital converter chip and read the conversion result; The microcontroller stores an adaptive configuration program, which is configured to perform the following steps: The resistance value of the piezoresistive sensor is obtained based on the voltage across the piezoresistive sensor measured by the first constant current value and the first gain. Based on the resistance value, the predicted voltage values ​​corresponding to the two ends of the piezoresistive sensor under multiple candidate constant current values ​​are obtained. Based on the comparison results between each predicted voltage value and the full-scale voltage corresponding to multiple candidate gains, candidate combinations in which the predicted voltage value does not exceed the full-scale voltage are selected. The target combination is determined from the selected candidate combinations based on the ratio of the predicted voltage value to the full-scale voltage in each candidate combination. The analog-to-digital converter chip is configured with the constant current value and gain in the target combination to acquire pulse signals.

2. The adaptive piezoresistive pulse signal acquisition circuit according to claim 1, characterized in that, The adaptive configuration procedure is configured to perform the step of obtaining the resistance value of the piezoresistive sensor based on the voltage across the piezoresistive sensor measured with a first constant current value and a first gain, specifically including: The analog-to-digital converter chip is controlled to measure the piezoresistive sensor with the first constant current value and the first gain to obtain the voltage across the piezoresistive sensor; The resistance value of the piezoresistive sensor is calculated based on the voltage across the piezoresistive sensor and the first constant current value.

3. The adaptive piezoresistive pulse signal acquisition circuit according to claim 1, characterized in that, The adaptive configuration procedure is configured to perform the step of obtaining the predicted voltage value across the piezoresistive sensor under multiple candidate constant current values ​​based on the resistance value, specifically including: Obtain multiple candidate constant current values; Each candidate constant current value is multiplied by the resistance value to obtain the predicted voltage value corresponding to each candidate constant current value.

4. The adaptive piezoresistive pulse signal acquisition circuit according to claim 1, characterized in that, The adaptive configuration procedure is configured to perform a step of selecting candidate combinations in which the predicted voltage values ​​do not exceed the full-scale voltage, based on a comparison between each predicted voltage value and the full-scale voltage corresponding to a plurality of candidate gains. Specifically, this includes: Obtain multiple candidate gains and the full-scale voltage corresponding to each candidate gain; Compare each of the predicted voltage values ​​with the full-scale voltage corresponding to each of the candidate gains; When the predicted voltage value is less than or equal to the full-scale voltage, the combination of the current candidate constant current value and the candidate gain is determined as the candidate combination.

5. The adaptive piezoresistive pulse signal acquisition circuit according to claim 1, characterized in that, The adaptive configuration procedure is configured to perform the step of determining a target combination from the selected candidate combinations based on the ratio of the predicted voltage value to the full-scale voltage in each candidate combination, specifically including: For each of the candidate combinations, calculate the ratio of the predicted voltage value to the full-scale voltage; Candidate combinations whose ratios fall within a preset preferred range are retained; The target combination is determined from the retained candidate combinations based on the preset priority.

6. The adaptive piezoresistive pulse signal acquisition circuit according to claim 5, characterized in that, The adaptive configuration procedure is configured to perform the step of determining a target combination from a pool of reserved candidate combinations based on a preset priority, specifically including: Among the remaining candidate combinations, the combination with the largest gain is selected in descending order of gain. When the gain is the same, select the combination with the smaller constant current value in ascending order of constant current value to determine the target combination.

7. The adaptive piezoresistive pulse signal acquisition circuit according to claim 1, characterized in that, The pseudo-differential voltage input channel includes a positive input terminal and a negative input terminal. The positive input terminal is used to connect to one end of the piezoresistive sensor connected to the constant current source output channel, and the negative input terminal is used to connect to one end of the piezoresistive sensor connected to analog ground.

8. The adaptive piezoresistive pulse signal acquisition circuit according to claim 1, characterized in that, The microcontroller is connected to the analog-to-digital converter chip via a serial peripheral interface and is used to configure the registers of the analog-to-digital converter chip and read the conversion results of the analog-to-digital converter chip.

9. The adaptive piezoresistive pulse signal acquisition circuit according to claim 1, characterized in that, The microcontroller is also used to detect the signal status during the acquisition of pulse signals, and when signal saturation or signal strength is detected to be lower than a preset threshold, the adaptive configuration program is re-executed.

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