JP4265432B2 - Data transmission device - Google Patents

Description

  The present invention relates to a data transmission apparatus.

In general, since a microcomputer (hereinafter referred to as “microcomputer”) handles digital values, for example, an analog signal output from a sensor or the like is converted into a digital signal using an A / D converter and then processed. . Specifically, taking a vehicle control microcomputer mounted on a vehicle as an example, an analog signal is output from an airflow sensor that detects the intake air amount of an engine or a water temperature sensor that detects the water temperature of a radiator. The digital signal is converted into a digital signal and then input to an ECU (Electronic Control Uint) microcomputer (see Non-Patent Document 1 below).
Hiroshi Shiga and Shuji Mizutani “Automotive Engineering Series Car Electronics”, Sankai-do Co., Ltd., p. 78-79

  Incidentally, many vehicle control ECUs equipped with such a microcomputer include an A / D converter, and in general, a sensor outputs an analog signal as a sensor signal. On the other hand, in the case of a control system such as a vehicle, the sensor and the ECU that performs signal processing on the output are often physically separated. Therefore, the sensor and the ECU for controlling the vehicle are generally configured to be electrically connected via a wire harness having a certain length. For this reason, there is a problem that the sensor signal is garbled or deteriorated due to external noise mixed between the sensor and the A / D converter of the ECU such as the wire harness. In particular, in the case of a vehicle control system, there are relatively many causes of external noise such as noise caused by spark plugs and other control microcomputers. There is a problem that transmission of sensor signals that are not present becomes more difficult.

  Further, as the detection resolution of the sensor increases, the sensor signal also becomes highly accurate. However, since the noise level due to external noise is higher than the minimum resolution level of the data based on the sensor signal, it is difficult for the ECU to receive high-precision data even if a high-precision A / D converter is used. There is also a problem. For example, if a data signal having a resolution of about 0.1 mV is taken out from a sensor signal having a full scale of DC5V, it can be detected by using an A / D converter of about 16 bits in principle. When the noise level reaches about several mV, the data signal is buried in the noise. Therefore, increasing the detection accuracy of the sensor causes a problem that it becomes more difficult to transmit the sensor signal from the sensor to the ECU.

  Further, if the power source for driving the sensor is different from the power source for the ECU that processes the sensor signal, the level of the sensor signal also changes relatively due to a change in one of the power supply voltages. On the other hand, as the accuracy of the sensor signal becomes higher, such a level fluctuation of the sensor signal tends to cause an error of the sensor signal. Therefore, there is a problem that such fluctuations in the power supply voltage make it difficult to transmit a highly accurate sensor signal.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a data transmission apparatus that enables highly accurate data transmission.

  In order to achieve the above object, the means described in claim 1 described in claims is adopted. According to this means, the transmission apparatus has A / D conversion means, transmission data storage means and transmission means, and the reception apparatus has reception means, reception data storage means and delta-sigma conversion means. In the transmission apparatus, the analog signal is oversampled, converted into a digital signal, and stored in the transmission data storage means. Then, the stored digital signal is taken out from the transmission data storage means and sent to the transmission medium. On the other hand, the receiving apparatus receives the digital signal sent from the transmitting means via the transmission medium and stores it in the received data storage means. Then, the digital signal taken out from the received data storage means is delta-sigma-converted with the oversampling ratio of the A / D conversion means of the transmission apparatus. “Oversampling” means sampling at a frequency exceeding the Nyquist frequency (oversampling frequency) in A / D conversion, and “oversampling ratio” means the ratio of the oversampling frequency to the Nyquist frequency. Say.

  By adopting the means according to claim 2, the digital signal taken out from the transmission data storage means is a difference from the digital signal one sample before, and is stored in the transmission data storage means. The amount of data can be reduced as compared with the case where all the digital signals are transmitted.

  By adopting the means according to claim 3, the analog signal is a sensor signal output from the sensor. Therefore, the sensor signal is a low-precision digital signal due to oversampling of the transmitter. Therefore, even if external noise is mixed on the transmission medium, it is not easily affected, and a low-precision digital signal is converted into a high-precision digital signal by the delta-sigma conversion of the receiving device, that is, a high-precision digital signal is obtained. A sensor signal can be obtained.

By adopting the means according to claim 4, the sensor is driven by a DC power source that drives the transmission device, so that even if the voltage of the DC power source fluctuates, the transmission device Similarly, the voltage of the DC power supply of the A / D conversion means, transmission data storage means and transmission means that constitutes fluctuates. Thereby, even if the power supply voltage of the sensor fluctuates , the power supply voltage of the A / D conversion means for converting the sensor signal that is an analog signal into a digital signal also fluctuates in the same way. It does not affect the oversampling of the A / D conversion means. In addition, since the transmission device and the reception device only exchange digital signals via the transmission medium, even if the power supply voltage of the transmission device fluctuates, it has no effect on the delta-sigma conversion of the reception device. There is nothing. Therefore, even if the voltage of the DC power supply of the sensor or the transmission device fluctuates, highly accurate data transmission can be achieved.
By the way, as a transmission medium according to claims 1 to 4, a LAN may be adopted as in claim 5 according to claims.

  In the first aspect of the invention, the transmitting device oversamples the analog signal and converts it into a digital signal. Therefore, as compared with the case where a high-precision digital signal is transmitted using an A / D conversion means having a high conversion accuracy, The conversion accuracy of the A / D conversion means itself can be lowered by the amount of oversampling. Therefore, by sending a large amount of low-accuracy digital signals to the transmission medium, it becomes possible to send the same amount of information to the receiving device as when using the A / D conversion means with high conversion accuracy. In addition, since the conversion accuracy of the A / D conversion means can be lowered, the immunity against external noise can be improved. On the other hand, the receiving apparatus receives such an oversampled digital signal and performs delta-sigma conversion at the oversampling ratio of the A / D conversion means of the transmitting apparatus. It can be converted into a digital signal. In other words, since a low-accuracy digital signal is transmitted by oversampling of the transmission device, even if external noise or the like is mixed on the transmission medium, it is not easily affected. Convert to a highly accurate digital signal. Therefore, highly accurate data transmission can be achieved.

  According to the second aspect of the present invention, since the digital signal taken out from the transmission data storage means is a difference from the digital signal one sample before, compared with the case where all the digital signals stored in the transmission data storage means are transmitted. The amount of data can be reduced. Thereby, the data amount of the low-accuracy digital signal increased by oversampling can be reduced. Therefore, highly accurate data transmission can be achieved with a small amount of data.

  In the invention of claim 3, since the sensor signal is transmitted as a low-precision digital signal by oversampling of the transmission device, even if external noise or the like is mixed on the transmission medium, the sensor signal is hardly affected. A low-precision digital signal can be converted into a high-precision digital signal by delta-sigma conversion, that is, a high-precision sensor signal can be obtained. Thus, for example, by providing the sensor with a transmission device, the sensor signal can be transmitted to the reception device as a highly accurate sensor signal. Therefore, highly accurate data transmission can be performed even in the sensor signal.

In the invention of claim 4, even if the voltage of the DC power supply of the sensor fluctuates, the power supply voltage of the A / D conversion means for converting the sensor signal that is an analog signal into a digital signal also fluctuates in the same way. The power supply voltage fluctuation does not affect the oversampling of the A / D conversion means. In addition, since the transmission device and the reception device only exchange digital signals via the transmission medium, even if the power supply voltage of the transmission device fluctuates, it has no effect on the delta-sigma conversion of the reception device. There is nothing. Therefore, even if the voltage of the DC power supply of the sensor or the transmission device fluctuates, highly accurate data transmission can be achieved.
In the invention of claim 5, the transmission medium according to claims 1 to 4 is applied to a LAN.
Therefore, for example, when the invention of claim 5 is used in a control system for a vehicle or the like, a sensor that outputs a sensor signal as an analog signal and an ECU as a receiving device that processes the sensor signal are physically separated. In many cases, an in-vehicle LAN using a wire harness having a certain length is generally used as a transmission medium. In a control system for a vehicle or the like, there is a high possibility that noise caused by a spark plug or other control microcomputer or the like is mixed into a cable or a connector constituting a wire harness of the in-vehicle LAN. This hinders data communication. However, according to the invention of claim 5, even if noise from a spark plug or other control microcomputer is mixed in the cable or connector of the in-vehicle LAN, high-accuracy data transmission is possible without being influenced by the noise. .
In the invention of claim 5, the transmission apparatus and the reception apparatus may be connected in a peer-to-peer (one-to-one) form, and a network form in which a plurality of transmission apparatuses and a plurality of reception apparatuses are connected in a bus shape or a star shape. May be taken. Incidentally, in the case of adopting a network form, the receiving apparatus adds a plurality of transmission codes by adding an identification code, a MAC address, etc. assigned to each transmitting apparatus to the header information of the digital signal transmitted via the LAN. The device can be identified.
The LAN is either a wired LAN (for example, a wired LAN for vehicle control called CAN (Controller Area Network)) or a wireless LAN (for example, IEEE802.11 series or Bluetooth). May be.

  Embodiments of a data transmission apparatus according to the present invention will be described below with reference to the drawings. In this embodiment, the transmission device of the data transmission device of the present invention is applied to the sensor unit 20 (20A, 20B, 20C), and the reception device of the data transmission device of the present invention is applied to the ECU 30, respectively. Therefore, a combination of the sensor unit 20 (transmission device) and the ECU 30 (reception device) corresponds to the data transmission device according to the present embodiment (hereinafter referred to as “the present data transmission device”). First, an outline of the data transmission apparatus constituted by the sensor unit 20 and the ECU 30 will be described with reference to FIG.

  As shown in FIG. 1, the sensor unit 20 of the present data transmission apparatus mainly includes a sensor element 21, a sensing circuit 22, a high-speed ADC 25, a data buffer 26, a communication driver / receiver 29, and the like. The sensor unit 20 has a function of oversampling a sensor signal (analog signal) output from the sensor element 21 configured as a sensor and the sensing circuit 22 by a high-speed ADC 25 with low conversion accuracy and converting the signal into a digital signal. A function of storing the digital signal in the data buffer 26, a function of transmitting the digital signal stored in the data buffer 26 to an in-vehicle LAN (Local Area Network) 50 by the communication driver / receiver 29, and the like.

On the other hand, the ECU 30 of the data transmission apparatus is mainly configured by a communication driver / receiver 31, a CPU α, and the like. The ECU 30 receives the digital signal sent from the sensor unit 20 via the in-vehicle LAN 50 and stores it in the data buffer 33 of the CPU α. The ECU 30 uses the delta sigma converter 35 of the CPU α to convert the digital signal extracted from the data buffer 33 to the delta sigma. A conversion function, a function of storing a digital signal subjected to delta-sigma conversion in the data register 37 , and the like.

  By providing each of such functions, in the present data transmission device, the sensor unit 20 sends the sensor signal of the sensing circuit 22 to the in-vehicle LAN 50 as a low-accuracy digital signal converted by oversampling. This is received and converted into a highly accurate digital signal by delta-sigma conversion. Thereby, as will be described later, in order to make it less susceptible to the influence of external noise or the like mixed in the in-vehicle LAN 50, highly accurate data transmission is enabled.

  In FIG. 1, the opposing sensor unit 20 and the ECU 30 are illustrated as being connected in a peer-to-peer (one-to-one) form by the in-vehicle LAN 50, but this clearly defines the concept of the data transmission apparatus. Is to do. Therefore, the sensor unit 20 and the ECU 30 may be connected peer-to-peer as shown in FIG. 1, but in this embodiment, for example, as shown in FIG. 2, a plurality of sensor units 20A, 20B, 20C, the ECU 30, and the illustration are omitted. A network configuration in which other ECUs or the like are connected in a bus shape or a star shape is adopted.

  Next, details of the configuration of the sensor unit 20 and the ECU 30 will be described with reference to FIG. In FIG. 2, a network configuration in which a plurality of sensor units 20 and one ECU 30 are connected to the in-vehicle LAN 50 is employed. Therefore, for convenience, “20A”, “20B”, and “20C” are assigned to the respective sensor units, and these are all the same as the sensor unit 20 described with reference to FIG. It is configured. Therefore, here, the sensor unit 20A will be described as a representative.

  As described with reference to FIG. 1, the sensor unit 20A includes the sensor element 21, the sensing circuit 22, the high-speed ADC 25, the data buffer 26, the communication driver / receiver 29, the noise generator 23, the addition circuit 24, and the difference. An extractor 27, a communication controller 28, a battery Batt, and the like are also provided.

  The sensor element 21 constitutes a sensor together with the sensing circuit 22 and can detect a physical quantity. Specifically, for example, a pressure detector called a pressure gauge corresponds to this. In the case of a pressure gauge, a Wheatstone bridge circuit using a resistor is generally formed as an equivalent circuit, and a voltage signal can be output by applying a DC voltage from a battery Batt to the outside. The battery Batt also supplies DC power to the sensing circuit 22 and the high-speed ADC 25 as will be described later. As a result, even if the DC voltage applied to the sensor element 21 and the sensing circuit 22 fluctuates, the DC voltage applied to the high-speed ADC 25 also fluctuates in the same manner. Preventing the impact. The sensor element 21 can output a voltage signal without applying a DC voltage from the outside, such as a thermocouple or a piezo element, in addition to a type that applies a DC voltage from the outside. Also good.

  The sensing circuit 22 has a function of amplifying the input voltage signal with a predetermined gain and outputting it as a sensor signal by inputting the voltage signal output from the sensor element 21. It can correspond to the “sensor” described in the range. The sensor signal output from the sensing circuit 22 is input to an adder circuit 24 at the next stage.

  The noise generator 23 has a function of generating, for example, white noise and outputting a noise value. Specifically, the noise generator 23 generates pseudo noise by a logic circuit or generates thermal noise by a semiconductor or the like. The noise value is obtained. The noise value output from the noise generator 23 is added to the sensor signal described above by the addition circuit 24 in the next stage. As a result, the AC component due to the noise value is added to the sensor signal, so that a relatively large DC component contained in the sensor signal can be converted into an AC component, enabling delta-sigma conversion by the ECU 30 described later. In addition, when the thermal noise etc. have generate | occur | produced with the electronic component which comprises the sensing circuit 22, and the noise value is superimposed on the sensor signal, the noise generator 23 and the addition circuit 24 become unnecessary.

  The high-speed ADC 25 is a so-called A / D converter that oversamples an analog signal and converts it into, for example, a digital signal quantized by 8 bits, and corresponds to the “A / D conversion means” recited in the claims. It is possible. Since the conversion accuracy of the high-speed ADC 25 is about 8 bits, the conversion accuracy is lower than that of an A / D converter that converts a digital signal such as 12 bits, 16 bits, or 24 bits, but the sampling frequency is, for example, It is set to 50 kHz (sampling interval 20 μS). Therefore, it is possible to perform high-speed sampling, that is, oversampling as compared with a general sampling frequency of 200 Hz (sampling interval 5 mS) of an A / D converter mounted on the vehicle control ECU. For example, if the Nyquist frequency is 200 Hz and the sampling frequency is 50 kHz, the oversampling ratio of the high-speed ADC 25 is 250 (= 50000 Hz / 200 Hz), and the converted digital signal is 250 times the data compared to the case of sampling at the Nyquist frequency. Amount. When oversampling is performed by the high-speed ADC 25 in this way, a large amount of low-precision digital data is output. The high-speed ADC 25 is driven by a battery Batt that drives the sensor element 21 and the sensing circuit 22. Accordingly, as described above, even if the DC voltage applied to the sensor element 21 or the like fluctuates, the DC voltage applied to the high-speed ADC 25 also fluctuates in the same manner, so that the sampling reference voltage also varies with this fluctuation. , Suppresses the influence on oversampling.

  The data buffer 26 has a function of temporarily storing the digital signal converted by the high-speed ADC 25 and outputting the stored digital signal in response to a request from the subsequent difference extractor 27 or the communication controller 28. This can correspond to the “transmission data storage means” described in the claims. Specifically, for example, it is configured by a semiconductor memory device such as DRAM or SRAM. The data buffer 26 is interposed between the high-speed ADC 25 and the difference extractor 27 or the communication controller 28, thereby absorbing a difference between the output speed of the high-speed ADC 25 and the processing speed of the difference extractor 27 or the communication controller 28. It plays the role of a vessel. Further, data management is performed so that data (8-bit configuration) of the digital signal converted by the high-speed ADC 25 can be extracted in units of 256. As a result, it is possible to output the difference extractor 27 and the communication controller 28 by regarding 8 bits × 256 pieces of data as 8 times oversampled data.

  The difference extractor 27 has a function of extracting a digital signal from the data buffer 26 and extracting a difference from the digital signal one sample before by the high-speed ADC 25. The sensor signal input from the sensing circuit 22 to the high speed ADC 25 via the adder circuit 24 is a continuous analog signal, and changes gradually with respect to the sampling interval of the high speed ADC 25. Therefore, the digital signal Dn converted at the sampling time t is not significantly different from the digital signal D (n-1) converted at the time t-Δt one sample before, and the time after one sample is also obtained. The same applies to the digital signal D (n + 1) converted to t + Δt. For example, when a digital signal converted by the high-speed ADC 25 is expressed by an 8-bit bit string, the digital signal D (n-1); 11011001 changes to a digital signal Dn; 11001001, and the digital signal D (n-1); As in the case of 10111001, the lower 4 bits (1001) do not change, and only the upper 4 bits change from (1101) to (1100) to (1011). Therefore, by extracting the change of the upper 4 bits as a difference, in this example, the data amount can be halved from 8 bits × 3 = 24 bits to 4 bits × 3 = 12 bits.

  As described above, the difference extractor 27 has a function of extracting difference data from the digital signal one sample before the digital signal extracted from the data buffer 26. Therefore, all the digital signals stored in the data buffer 26 are directly used. The amount of data can be reduced compared to the case of sending. Thereby, it is possible to reduce the amount of data of a low-precision digital signal that tends to increase due to oversampling by the high-speed ADC 25. Therefore, highly accurate data transmission is possible with a small amount of data. Note that even if a digital signal is output directly from the data buffer 26 to the communication controller 28 without passing through the difference extractor 27, that is, without extracting the difference data, as in the route indicated by the broken-line arrow shown in FIG. good. Thereby, the digital signal converted by the high-speed ADC 25 is transferred to the communication controller 28 as it is.

  The communication controller 28 can control the communication driver / receiver 29 and can correspond to the “transmission means” described in the claims together with the communication driver / receiver 29. Therefore, conceptually, the communication driver / receiver 29 and the function of sending the digital signal extracted from the difference extractor 27 or the data buffer 26 to the in-vehicle LAN 50 are provided. In this embodiment, since the in-vehicle LAN 50 is used as a transmission medium, for example, communication control according to a wired network communication protocol called CAN (Controller Area Network) is performed on the communication driver / receiver 29. ing.

  The communication driver / receiver 29 has a function of sending a digital signal extracted from the difference extractor 27 or the data buffer 26 to the in-vehicle LAN 50 under the control of the communication controller 28. This can correspond to “transmission means”. Specifically, not only simply sending a digital signal to the in-vehicle LAN 50, but also exchanging control information with the ECU 30 and other sensor units 20B and 20C according to, for example, the CAN communication protocol. If necessary, it also has the function of a receiving device. Therefore, it is called “communication driver / receiver”.

  The in-vehicle LAN 50 is a wired LAN for vehicle control called CAN, for example, and is set to a communication speed of several tens of kbps to 500 kbps, for example. In the present embodiment, since a large amount of digital data is flowed by oversampling with the high-speed ADC 25, it is desirable to use a higher-speed LAN (for example, FlexRay or the like) of about 500 kbps to 10 Mbps. Further, the present invention is not limited to a wired LAN. For example, a wireless LAN such as IEEE802.11 series or Bluetooth may be used as a transmission medium. In this case, it is necessary to change the communication driver / receiver 29 and the communication controller 28 to be compatible with the wireless LAN.

  Here, the in-vehicle LAN 50 is wired in the vehicle by a twisted pair cable, a coaxial cable, or the like. Therefore, there is a high possibility that noise from the ignition plug or other control microcomputer or the like is mixed into the cable or connector of the in-vehicle LAN 50, and the mixed noise becomes a so-called external noise and hinders data communication by the in-vehicle LAN 50. Specifically, as described in the section “Problems to be Solved by the Invention”, when a data signal having a resolution of about 0.1 mV is extracted from a sensor signal having a DC5V full scale, the noise level of external noise When the voltage reaches about several mV, the data signal is buried in this noise. For this reason, there is a situation where it is difficult to use an A / D converter of about 16 bits which is possible in principle.

  Therefore, in the embodiment, as described above, the sensor unit 20 (20A) performs oversampling by increasing the sampling frequency instead of making the A / D conversion by the high-speed ADC 25 about 8 bits with low accuracy. As a result, the amount of reduced accuracy is compensated by the amount of data of the digital signal (for example, 8 bits × 256) increased by oversampling, and this is subjected to delta-sigma conversion by the ECU 30 to be described so that highly accurate data transmission can be performed. It is possible.

  As shown in FIG. 2, the ECU 30 includes a communication driver / receiver 31, a communication controller 32, a data buffer 33, a delta-sigma converter 35, a data register 37, and the like. The communication controller 32, the data buffer 33, the delta-sigma converter 35, and the data register 37 are incorporated in a CPU α that is an ASIC (Application Specific Integrated Circuit).

  The communication driver / receiver 31 has substantially the same function as the communication driver / receiver 29 of the sensor unit 20A described above. In particular, a digital signal sent from the communication driver / receiver 29 of the sensor unit 20A is transmitted via the in-vehicle LAN 50. Therefore, it can correspond to the “reception means” described in the claims. In the present embodiment, for example, the received digital signal is output to the communication controller 32 of the CPU α as an n-bit parallel output.

  The communication controller 32 has substantially the same function as the communication controller 28 of the above-described sensor unit 20A, and together with the above-described communication driver / receiver 31, can correspond to the “receiving means” described in the claims. is there. In this embodiment, since the in-vehicle LAN 50 by CAN is used as a transmission medium, communication control according to the CAN communication protocol is performed on the communication controller 32.

The data buffer 33 also has substantially the same function as the communication controller 28 of the above-described sensor unit 20A, temporarily stores the digital signals received by the communication driver / receiver 31 and the communication controller 32, and at the subsequent delta. It has a function of outputting a stored digital signal in response to a request from the sigma converter 35, and can correspond to "reception data storage means" described in the claims. Specifically, for example, it is configured by a semiconductor memory device such as DRAM or SRAM. The data buffer 33 is interposed between the communication controller 32 and the delta sigma converter 35, thereby acting as a buffer that absorbs the difference between the output speed of the communication controller 32 and the conversion speed of the delta sigma converter 35. Plays. In addition, data management is performed so that data (8-bit configuration) of digital signals received by the communication driver / receiver 31 and the communication controller 32 can be extracted in units of 256. As a result, it is possible to output 8 bits × 256 pieces of data as 8 times oversampled data to the delta sigma converter 35.

  The delta-sigma converter 35 has a function of performing delta-sigma conversion on the digital signal extracted from the data buffer 33 at the oversampling ratio of the high-speed ADC 25 of the sensor unit 20A. It can correspond to. Specifically, for example, by extracting the digital signal data (8-bit configuration) stored in the data buffer 33 in units of 256 as described above, 8 bits × 256 data is oversampled by 8 times. Consider delta-sigma conversion. As a result, a resolution equivalent to 16 bits can be obtained, and the converted sensor signal data (16-bit configuration) is stored in the data register 37. The data register 37 is, for example, a general-purpose register of the CPU α and stores the sensor signal data converted by the delta-sigma converter 35, and enables the data to be transferred in response to a request from the control unit or arithmetic unit of the CPU α. ing.

  In addition, this ECU30 adds the identification code, MAC address, etc. which were allocated for every sensor unit 20A-20C to the header information of the digital signal sent via in-vehicle LAN50, for example, and other than sensor unit 20A In addition, sensor signals having a resolution equivalent to 16 bits can be received from the sensor unit 20B and the sensor unit 20C as well as the sensor unit 20A.

  As described above, according to this data transmission apparatus, the sensor unit 20 oversamples the sensor signal (analog signal) output from the sensor element 21 and the sensing circuit 22 and converts it into a digital signal. Compared with the case where a high-precision digital signal is transmitted using an A / D converter (for example, 16 bits) with high accuracy, the conversion accuracy of the high-speed ADC 25 can be lowered (for example, 8 bits) by the amount of oversampling. Therefore, by sending a large amount of low-precision digital signals to the transmission medium (8 bits × 256), it is possible to send the same amount of information to the ECU 30 as when using an A / D converter with high conversion accuracy. Become. Moreover, since the conversion accuracy of the A / D converter can be lowered to, for example, about 8 bits, the immunity against external noise can be improved.

  On the other hand, the ECU 30 receives such oversampled digital signal (8 bits × 256) and performs delta sigma conversion by the delta sigma converter 35 at the oversampling ratio of the high-speed ADC 25 of the sensor unit 20. As a result, the in-vehicle LAN 50 can convert a low-precision digital signal (8 bits × 256) into a high-precision digital signal (equivalent to 16 bits). That is, since a large amount of low-accuracy digital signals are transmitted by oversampling of the sensor unit 20, even if external noise or the like is mixed on the in-vehicle LAN 50, it is difficult to be affected by the delta-sigma converter 35 of the ECU 30. The conversion converts a low-precision digital signal into a high-precision digital signal. Therefore, highly accurate data transmission can be achieved.

It is a block diagram which shows the structure outline | summary of the data transmission apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the sensor unit and ECU of the data transmission apparatus which concern on this embodiment.

Explanation of symbols

20, 20A, 20B, 20C ... sensor unit (transmitting device)
21 ... Sensor element (sensor)
22 ... Sensing circuit (sensor)
23 ... Noise generator 24 ... Adder circuit 25 ... High-speed ADC (A / D conversion means)
26: Data buffer (transmission data storage means)
27 ... Difference extractor 28 ... Communication controller (transmission means)
29 ... Communication driver / receiver (transmission means)
30 ... ECU (receiving device)
31. Communication driver / receiver (reception means)
32. Communication controller (reception means)
33. Data buffer (received data storage means)
35 ... Delta sigma converter (delta sigma conversion means)
37 ... Data register 50 ... In-vehicle LAN (transmission medium)
α ... CPU
Batt ... Battery (DC power supply)

Claims (5)

A / D conversion means for oversampling an analog signal to convert it to a digital signal, transmission data storage means for storing the converted digital signal, and taking out the stored digital signal from the transmission data storage means to a transmission medium A transmission device having a transmission means for transmitting;
Receiving means for receiving the digital signal transmitted from the transmitting means via the transmission medium, received data storing means for storing the received digital signal, and the digital signal taken out from the received data storing means for the A / A receiver having delta-sigma conversion means for performing delta-sigma conversion at an oversampling ratio of the D conversion means;
A data transmission device comprising:   2. The data transmission apparatus according to claim 1, wherein the digital signal extracted from the transmission data storage means is a difference from the digital signal one sample before.   3. The data transmission apparatus according to claim 1, wherein the analog signal is a sensor signal output from a sensor.   The data transmission device according to claim 3, wherein the sensor is driven by a DC power source that drives the transmission device. The data transmission apparatus according to claim 1, wherein the transmission medium is a LAN (Local Area Network).

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