Data transmission system

Abstract

The objective is to provide a data transmission system that significantly reduces the required wiring, enabling system miniaturization and improved design flexibility. [Solution] A data transmission system that shares power supply and data transmission comprises a first device and a second device. The first device comprises voltage control means and current monitoring means. The second device comprises a variable current source and a control unit. The first device transmits changes in voltage values ​​controlled by the voltage control means as data to the second device, and detects and receives changes in current values ​​transmitted by the second device as data using the current monitoring means. The control unit of the second device transmits data to the first device based on changes in current values ​​modified by the variable current source.

Description

Technical Field

[0001] The present invention relates to a data transmission system.

Background Art

[0002] For the purpose of reducing the wiring of inter-device communication lines, a communication method that shares a power supply line and a communication signal line has been devised. This method eliminates the signal line by superimposing a communication signal on the power supply. In existing communication methods that share a power supply line and a communication signal line, there has been no method capable of realizing a simple communication method suitable for throughputs exceeding several Mbps used in embedded applications and enabling multi-drop (one-to-many communication). For example, methods that use a bandwidth of several Gbps as the signal line bandwidth such as GMSL and CoaXPress are excessive for communications of about several Mbps, and the circuits become complex and large. Also, many of them do not support multi-drop. 1-Wire, which is developed as a simpler and lower-speed communication method assuming embedded applications, supports multi-drop, but due to the use of the bus voltage for both transmission and reception, the communication speed is at most 120 kbps, making it difficult to achieve throughputs exceeding several Mbps.

[0003] As a prior art for the purpose of reducing the wiring of inter-device communication lines, a technique assuming unidirectional communication from a plurality of devices to a host (transmission from the host is only at the communication start timing) has been proposed. In this first prior art, the topology is a daisy chain type, and four-level symbol codes are used for data transmission due to bus current fluctuations (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when attempting to implement a multi-drop (one-to-many communication) communication method suitable for throughputs exceeding several Mbps used in embedded applications using conventional communication methods that share power supply lines and communication signal lines, complex or large load circuits such as PLCs (Programmable Logic Controllers) and GMSLs (Gigabit Multimedia Serial Links) were required, making it impossible to miniaturize the system.

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a data transmission system that can miniaturize the system and improve design flexibility without using complex or large load circuits. [Means for solving the problem]

[0007] (1) To achieve the above objective, a data transmission system according to one aspect of the present invention is a data transmission system that shares power supply and data transmission, comprising a first device and a second device, wherein the first device comprises voltage control means and current monitoring means, and the second device comprises a variable current source and a control unit, the first device transmits changes in voltage values ​​controlled by the voltage control means as data to the second device, the control unit of the second device transmits data to the first device based on changes in current values ​​changed by the variable current source, and the first device detects and receives changes in current values ​​transmitted by the second device as data using the current monitoring means.

[0008] (2) In one embodiment described in (1) above, the transmission from the first device to the second device may be performed such that the bus that transmits data due to changes in voltage value (e.g., Vbus) is not always at an L level during the period allocated for the transmission of 1 bit, and the transmission from the second device to the first device may be performed during the period when the bus that transmits data due to changes in voltage value is not at an L level.

[0009] (3) In one embodiment described in (1) or (2) above, the voltage value controlled by the voltage control means may be the negation of RTI (Return to Zero inverted), and the signal of the current value changed by the variable current source may be NRZ (Non Return to Zero).

[0010] (4) In one embodiment described in (1) above, the voltage control means may transmit changes in voltage values ​​as data to the second device, with a first voltage value (e.g., Vcc_H) lower than the power supply voltage by a first predetermined value as the first level (e.g., H level) and a second voltage value (e.g., Vcc_L) higher than the ground level by a second predetermined value as the second level (e.g., L level).

[0011] (5) In one embodiment described in (1) or (4) above, the variable current source may transmit changes in current values ​​as data to the first device, with a first current (e.g., Ibus_H) that is a third predetermined value lower than the maximum current value as the first level, and a second current value (e.g., Ibus_L) that is a fourth predetermined value higher than the zero level as the second level. [Effects of the Invention]

[0012] According to the above (1) to (5), the required wiring can be significantly reduced, and the system can be miniaturized and its design flexibility improved. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of the appearance of the data transmission system in the embodiment when it is a robot. [Figure 2] This figure shows an example configuration of the data transmission system in the embodiment when used with a robot. [Figure 3] This figure shows an example configuration of functions related to data transmission and reception of a control device according to an embodiment, and an example configuration of functions related to data transmission and reception of a device. [Figure 4] This figure shows an example of data transmission and reception according to the embodiment. [Figure 5] FIG. is a diagram showing a configuration example of a host side and a device side according to the prior art 1-Wire. [Figure 6] FIG. is a diagram showing a configuration example of data transmission and reception of a control circuit in the first embodiment. [Figure 7] FIG. is a diagram showing an example of data transmission and reception in the first embodiment and the relationship between the bus state and data transmission. [Figure 8] FIG. is a diagram showing an outline of data transmission and reception timing in the second embodiment. [Figure 9] FIG. is a diagram showing data pattern examples such as NRZ and RZI. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings used in the following description, the scales of each member are appropriately changed in order to make each member recognizable. In all the drawings for explaining the embodiments, those having the same function are denoted by the same reference numerals, and repeated explanations are omitted. In addition, “based on XX” as used in the present application means “at least based on XX”, and includes cases where it is based on another element in addition to XX. Also, “based on XX” is not limited to the case where XX is directly used, and includes cases where it is based on something obtained by performing operations or processing on XX. “XX” is an arbitrary element (for example, arbitrary information). <000*085> <Configuration Example of Data Transmission System> First, a configuration example of the data transmission system 1 will be described. FIG . 1 is a diagram showing an external appearance example when the data transmission system of the present embodiment is a robot. As shown in FIG. 1, the data transmission system 1 includes, for example, a control device *2 (first device) and a device 3 (second device). <*000088>

[0016] The control device 2 is composed of, for example, a personal computer, or a CPU (Central Processing Unit), a storage unit, etc. The control device 2 and the device 3 are connected to each other via a bus 4 as will be described later. The control device 2 may be provided inside the robot or may be connected outside the robot.

[0017] The device 3 is, for example, the arm and hand, leg, head, waist, etc. of the robot. In FIG. 1, the mechanism part including the arm and hand shows an example of the device 3. The first device 310 is, for example, a mechanism part corresponding to the elbow of the right arm. The second device 320 is, for example, a mechanism part corresponding to the wrist of the right arm. Note that the examples of the first device 310 and the second device 320 described above are just examples and are not limited thereto. For example, the first device 310 may be a mechanism part corresponding to the elbow of the left arm, and the second device 320 may be a mechanism part corresponding to the wrist of the left arm. Thus, the second device 320 is a mechanism part connected to the end of the first device 310.

[0018] The bus 4 is wired inside the robot. As will be described later, data transmitted from the control device 2 to the device 3 is superimposed on the bus 4 by the control device 2 varying the bus voltage, and data transmitted from the device 3 to the control device 2 is superimposed on the bus 4 by the device 3 varying the bus current.

[0019] FIG. 2 is a diagram showing a configuration example when the data transmission system of the present embodiment is a robot. The control device 2 (the first device) includes, for example, a transmission unit 21, a reception unit 22, a first control unit 23, a drive circuit 24, and a storage unit 25. The device 3 (the second device) includes n (n is 1 or more) first devices 310, second devices 320, ···. The first device 310 includes, for example, a functional unit 311, a second control unit 312, a variable current source 313, and a reception unit 314. The second device 320 includes, for example, a functional unit 321, a second control unit 322, a variable current source 323, and a reception unit 324.

[0020] (Control device) The transmitting unit 21 includes, for example, a bus voltage control circuit 211 (voltage control means). The bus voltage control circuit 211 transmits the transmission data output by the first control unit 23 to the device 3 by varying the bus voltage.

[0021] The receiving unit 22 includes, for example, a bus current monitoring circuit 221 (current monitoring means). The bus current monitoring circuit 221 detects the data output by device 3 by monitoring fluctuations in the bus current and outputs the detected data to the first control unit 23.

[0022] The first control unit 23 controls each part of the control device 2, such as transmitting data from the transmitting unit 21 and receiving data from the receiving unit 22.

[0023] The drive circuit 24 generates a drive signal in response to a control instruction generated by the first control unit 23. The drive circuit 24 may also be provided within the device 3.

[0024] The memory unit 25 stores thresholds, formulas, programs, etc., used by the first control unit 23.

[0025] (device) The explanation will use the first device 310 as an example, out of the first device 310 and the second device 320. Note that each of the nth devices may have the same configuration or may be different. Furthermore, the nth device may also include an actuator. Additionally, the nth device may include a drive circuit that drives the actuator in accordance with control instructions included in the transmitted data.

[0026] The functional unit 311 may be, for example, a pressure sensor, tactile sensor, acceleration sensor, 6-axis sensor, or image sensor that detects some kind of information. Alternatively, the functional unit 311 may be an encoder, brightness sensor, temperature sensor, sound pickup device, lamp, or the like. Alternatively, the functional unit 311 may be an actuator equipped with an encoder, for example. Furthermore, the functional unit 311 may not involve detection or driving of a storage medium or the like.

[0027] The second control unit 312 acquires the detection data detected by the functional unit 311. The second control unit 312 controls the variable current source 313 to vary the current value of the bus 4 and transmits the acquired detection data to the control device 2. The second control unit 312 drives the actuator based on the data received by the receiving unit 314 from the data transmitted by the control device 2.

[0028] The variable current source 313 varies the current value supplied to the bus 4 according to the control of the second control unit 312.

[0029] The receiving unit 314 detects and receives the transmission data sent by the control device 2 based on the voltage change of the bus 4.

[0030] (Sending and receiving data) Next, data transmission and reception will be explained. Figure 3 shows an example configuration of the functions related to data transmission and reception of the control device according to this embodiment, and an example configuration of the functions related to data transmission and reception of the device. Power supply and data transmission are performed via wired connections.

[0031] First, we will explain an example configuration related to data transmission and reception of the control device 2. The first control unit 23 is grounded (connected to GND). The input of the bus voltage control circuit 211 and the output of the bus current monitoring circuit 221 are also connected to the first control unit 23.

[0032] The bus voltage control circuit 211 is supplied with power Vcc and is grounded (connected to GND). The input of the bus voltage control circuit 211 is connected to the first control unit 23, and the output is connected to the bus 4. In the following description, the bus from the control device 2 to the device 3 due to voltage changes is referred to as Vbus (a bus that transmits data by changing voltage values).

[0033] The bus current monitoring circuit 221 has its input connected to the bus 4 via a current detection unit, and its output connected to the first control unit 23. In the following description, the bus from device 3 to control unit 2 due to current changes is referred to as Ibus (a bus that transmits data based on changes in current values).

[0034] Next, we will explain an example configuration related to data transmission and reception of device 3, using the first device 310 as an example. The functional unit 311 is connected to the second control unit 312, for example, via a peripheral interface g1. The peripheral interface g1 can be, for example, a UART (Universal Asynchronous Receiver / Transmitter), SPI (Serial Peripheral Interface), I2C (Inter-Integrated Circuit), analog signals, digital signals, etc. The functional unit 311 is also grounded (connected to GND).

[0035] The second control unit 312 is grounded (connected to GND). The input of the receiving unit 314 is connected to the second control unit 312, and the control terminal of the variable current source 313 is connected to it.

[0036] The variable current source 313 has a control terminal connected to the second control unit 312, one end connected to the input of the receiving unit 314, the anode of diode D1, and bus 4, and the other end connected to ground (GND).

[0037] The receiving unit 314 has an input connected to one end of the variable current source 313, the anode of diode D1, and bus 4, and an output connected to the second control unit 312.

[0038] Diode D1 has its anode connected to the bus 4, the input of the receiver 314, and one end of the variable current source 313, and its cathode connected to one end of capacitor C1 and the internal power supply Vdd of device 3.

[0039] Capacitor C1 has one end connected to the cathode of diode D1 and the internal power supply Vdd, and the other end connected to ground (GND). Diode D1 is connected for rectification. Capacitor C1 is connected for rectification, ripple and noise reduction, etc.

[0040] Next, we will explain the data transmission and reception of the control device 2. The bus voltage control circuit 211 transmits the transmission data output by the first control unit 23 to the device 3 by varying the bus voltage. The bus current monitoring circuit 221 detects the data output by device 3 by monitoring fluctuations in the bus current and outputs the detected data to the first control unit 23.

[0041] Next, we will explain how device 3 sends and receives data. The second control unit 312 controls the variable current source 313 to vary the current value flowing through the bus 4, thereby transmitting data from the device 3 to the control device 2. The receiving unit 314 detects and receives the transmission data output by the control device 2 by monitoring the bus voltage.

[0042] Figure 4 shows an example of data transmission and reception according to this embodiment. In Figure 4, the horizontal axis represents time (msec), and the vertical axis represents voltage change (V) and current change (mA). Waveform g10 is an example of the data waveform and timing transmitted from the control device 2 to the device 3. Waveform g20 is an example of the data waveform and timing transmitted from the device 3 to the control device 2.

[0043] For example, during the period from time t1 to t2, the control device 2 uses a bus voltage control circuit 211 to change the voltage of Vbus to, for example, 0 (V) or Vcc and transmit data to device 3.

[0044] For example, during the period from time t3 to t4, device 3 transmits data to control device 2 by having the second control unit 312 control the variable current source 313 to change the current of Ibus. The transmitted data may include identification information to identify the functional unit. For example, if the functional unit can be identified from the transmission timing, etc., the data does not need to include identification information.

[0045] (Comparative example) Here, we will explain data transmission and reception using a power line with conventional 1-Wire technology. Figure 5 shows an example of the host side configuration and the device side configuration using conventional 1-Wire technology. In conventional technology, host 900 transmits and receives data with 1-Wire devices 920, 930, ... via Vbus. In 1-Wire, as shown in Figure 5, signal transmission using an open-drain configuration is necessary to avoid bus collisions between host 900 and the devices.

[0046] Code g901 represents the schematic configuration of the data transmission and reception function unit of the host 900. In the host 900, the port controller 901 controls the FET (Tr1) to vary the voltage and transmit data, and the bus voltage monitoring unit 902 monitors Vbus to detect and receive data from device 920 or 930. Code g931 represents the schematic configuration of the data transmission and reception function section of device 930. In device 930, the interface controller 931 controls the FET (Tr2) to vary the voltage and transmit data, while the bus voltage monitoring unit 932 monitors Vbus to detect and receive data from the host 900. A device is also connected to the interface controller 931.

[0047] In this conventional configuration, an open-drain configuration is required to avoid bus collisions, making it difficult to increase the speed of bus voltage fluctuations. Furthermore, as the frequency of data transmission increases, the power supply from the bus voltage becomes unstable. In addition, although conventional technology supports multidrop, because both transmission and reception use the bus voltage, the specification limit for communication speed is 120kbps, and it cannot be applied to communication at higher speeds. Moreover, in conventional technology, as the communication frequency increases, the power supply to the Vbus becomes unstable.

[0048] In contrast, according to this embodiment, for a communication method that uses the same power supply line and communication signal line for bidirectional communication between one control device 2 and multiple devices 3, data transmission from the control device 2 to the device 3 is performed using bus voltage, and data transmission from the device 3 to the control device 2 is performed using bus current, thereby achieving both bidirectional communication exceeding several Mbps and power supply with a simple circuit configuration.

[0049] In this embodiment, the control device 2 includes a bus voltage control circuit 211 and a bus current monitoring circuit 221. In this embodiment, the bus voltage control circuit 211 supplies power to the device 3 and transmits data, while the bus current monitoring circuit 221 receives data from fluctuations in the device load current. In addition, in this embodiment, the device 3 is equipped with a variable current source 313 (323, ...), which transmits data to the control device 2 by increasing or decreasing its current value, and also suppresses fluctuations in the bus current caused by the device 3 itself.

[0050] This is because it allows for bus voltage fluctuations without the open-drain configuration required in conventional technology. Furthermore, the bus voltage control circuit 211, which is the transmission function in this embodiment, is open-drain. As a result, communication speeds can be increased (over several Mbps) in this embodiment. In addition, according to this embodiment, since bus voltage fluctuations are not used for data transmission from the device, the impact on Vbus due to increased communication frequency can be reduced. Moreover, according to this embodiment, since the transmission from the device is current-based, the immunity to voltage noise when transmitting data from the device 3 to the control device 2 can be improved.

[0051] Due to this configuration, the data transmission system 1 of this embodiment can be made smaller compared to conventional systems. For example, in devices that require the installation of many sensors in a small space, such as the fingers of a robot hand, minimizing the wiring for sensors is effective in reducing the size of the device and improving design flexibility, reliability, and durability when there are movable parts.

[0052] <First Example> In the first embodiment, full-duplex communication can be achieved by changing the voltage supplied to the circuit of the control device 2. In the configuration shown in Figure 3, when the voltage of Vbus is 0 (V), the current of Ibus is near 0 (A), so device 3 cannot control the bus current and full-duplex communication cannot be achieved. For this reason, in the first embodiment, Vcc_H and Vcc_L are connected to the bus voltage control circuit 211A as shown in Figure 6. Figure 6 is a diagram showing an example of the data transmission and reception configuration of the control circuit in the first embodiment.

[0053] The first control unit 23 is grounded (connected to GND). The input of the bus voltage control circuit 211A and the output of the bus current monitoring circuit 221 are also connected to the first control unit 23.

[0054] The bus voltage control circuit 211A is supplied with power supply Vcc_H and connected to Vcc_L instead of ground. That is, the bus voltage control circuit 211A transmits the change in voltage value as data to device 3, with a first voltage value (Vcc_H) which is a first predetermined value lower than the power supply voltage Vcc as the first level (H level), and a second voltage value (Vcc_L) which is a second predetermined value higher than the ground level (0(V)) as the second level (L). The variable current source 313 transmits the change in current value as data to control device 2, with a first current (Ibus_H) which is a third predetermined value lower than the maximum current value as the first level (H), and a second current value (Ibus_L) which is a fourth predetermined value higher than the zero level as the second level (L).

[0055] Note that Vcc_H may be the same voltage as Vcc, or it may be a voltage lower than Vcc by a first predetermined value (for example, Vcc=5V, Vcc=4.3V, etc.). Also, Vcc_L is a voltage higher than 0V by a second predetermined value, for example, 0.7V, 2V, 5V, etc. That is, the relationship between Vcc_H and VccL is Vcc_H>Vcc_L>0. The bus voltage control circuit 211A has its input connected to the first control unit 23 and its output connected to the bus 4.

[0056] Figure 7 shows an example of data transmission and reception in the first embodiment, and the relationship between the bus state and data transmission. In Figure 7, the symbol g30 shows an example of the waveform and timing of data transmission and reception. In the figure of symbol g30, the horizontal axis represents time (msec), and the vertical axis represents voltage change (V) and current change (mA). Waveform g31 is an example of the data waveform and timing transmitted from the control device 2 to the device 3. Waveform g20 is an example of the data waveform and timing transmitted from the device 3 to the control device 2. As shown in the figure of symbol g30, according to the first embodiment, for example, during the period from time t11 to t12, data transmission from the control device 2 to the device as shown in waveform g31 and data transmission from the device to the control device 2 as shown in waveform g32 can be performed simultaneously.

[0057] In Figure 7, the symbol g40 represents the relationship between the bus state and data transmission. The horizontal axis represents the current value of Ibus, and the vertical axis represents the voltage value of Vbus. At point g41, the data from control unit 2 to the device is at the H level (Vcc_H), and the data from the device to control unit 2 is at the L level (Ibus_L). At point g42, the data from control unit 2 to the device is at the H level (Vcc_H), and the data from the device to control unit 2 is at the H level (Ibus_H). At point g43, the data from control unit 2 to the device is at the L level (Vcc_L), and the data from the device to control unit 2 is at the L level (Ibus_L). At point g44, the data from control unit 2 to the device is at the L level (Vcc_L), and the data from the device to control unit 2 is at the H level (Ibus_H).

[0058] As described above, in the first embodiment, full-duplex communication can be achieved by setting the L-level voltage of the bus voltage control circuit 211A to a value higher than 0V.

[0059] <Second Example> In the second embodiment, full-duplex communication is achieved without changing the configuration of the control device 2. For this reason, the configuration of the data transmission system 1 and the control device 2 is the same as in Figure 3 described above.

[0060] In the second embodiment, in order to support full-duplex communication without changing the circuit configuration, the transmission path codes from the control device 2 to the device 3 and from the device to the control device 2 were set to satisfy the following conditions. Condition I. During the period allocated for 1-bit transmission from control device 2 to device 3, the bus transmitting data will not always be 0(V) due to changes in voltage value (including the L level if the L level is 0(V)). Condition II. Transmission from device 3 to control device 2: Significant data transmission can be performed during periods when Vbus is not 0 (V).

[0061] Examples of transmission line codes that satisfy the above conditions I and II are as follows: In the data transmitted from control device 2 to device, the transmission path code is the negation of RZI (Return to Zero inverted). Also, in the data transfer from device 3 to control device 2, the transmission path code is NRZ (Non Return to Zero). In addition to using the transmission path codes described above, staggering the reading timings of Vbus and Ibus enables Ibus transmission, supporting full-duplex communication. For example, even if the data transmission period from control device 2 to device 3 includes a period where Vbus=0(V), simultaneous transmission is possible. Furthermore, since the transmission period does not overlap with the period where Vbus=0(V), transmission via Ibus becomes possible. Furthermore, RZI transmission can shorten the period during which Vbus=0 compared to NRZ, thus contributing to improved stability of Vbus power supply.

[0062] Figure 8 shows an overview of the timing of data transmission and reception in the second embodiment. The horizontal axis represents time, and the vertical axis represents the signal levels of Vbus and Ibus. Waveform g50 is an example of the data waveform and timing from the control device 2 to the device 3 for Vbus. Waveform g50 is an example of the data waveform and timing from the device 3 to the control device 2 for Ibus. Note that Ibus_H is "1" and Ibus_L is "0".

[0063] During the period from time t21 to t22, the Vbus level is "0". During the period from time t22 to t23, the Ibus level is "0". During the period from time t23 to t24, the Vbus level is "0". From time t24 onwards, the Vbus level is "1". During the period from time t24 to t25, the Ibus level is "1". During the period from time t25 to t26, the Ibus level is "1". From time t26 onwards, the Ibus level is "1".

[0064] Figure 9 shows examples of data patterns for NRZ, RZI, etc. In Figure 9, the horizontal axis represents time (msec), and the vertical axis represents the signal level (high or low level). Note that the example in Figure 9 shows the waveform patterns for each code when the data is "10100111". Waveform g71 is the clock waveform, wave g72 is the NRZ waveform, wave g73 is the RZ waveform, wave g74 is the NRZI waveform, wave g75 is the RZI waveform, and wave g76 is the Manchester code waveform.

[0065] As described above, full-duplex communication can be achieved according to the first and second embodiments.

[0066] In the first and second embodiments described above, examples of communication with one device 3 were explained, but the control device 2 can also communicate with two or more devices 3 simultaneously. For example, by assigning a specific Ibus signal level to each device 3, signal interference can be avoided due to the difference in signal levels, allowing for the separation and reception of data from each of the multiple devices 3.

[0067] As described above, in the above embodiment, half-duplex communication can be performed regardless of whether the circuit is modified or not. Furthermore, in the above embodiment, full-duplex communication can be performed by modifying the circuit. Moreover, according to the above embodiment, full-duplex communication can be performed with a specific transmission path code without modifying the circuit. In other words, restrictions on the transmission path code are imposed only when full-duplex communication is performed without modifying the circuit.

[0068] In the example described above, a robot was used as an example of the data transmission system 1, but the data transmission system 1 is not limited to this. It is preferable to apply it to equipment where the location where the functional unit 311 (or 321, ...) is attached is movable and confined.

[0069] Furthermore, a program for realizing all or part of the functions of the first control unit 23 of the control device 2, or all or part of the functions of the second control unit 312 (or 323, ...) of the device 3, may be recorded on a computer-readable recording medium, and all or part of the processing performed by the first control unit 23 may be performed by loading the program recorded on this recording medium into a computer system and executing it, thereby performing all or part of the processing performed by the second control unit 312 (or 323, ...). Here, "computer system" includes hardware such as an OS and peripheral devices. Furthermore, "computer system" also includes a WWW system equipped with a homepage provisioning environment (or display environment). Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, "computer-readable recording medium" also includes volatile memory (RAM) inside a computer system that acts as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, which holds the program for a certain period of time. Alternatively, some or all of these components may be implemented by hardware (including circuitry) such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), GPU (Graphics Processing Unit), or SOC (System On Chip), or by the collaboration of software and hardware.

[0070] Furthermore, the above program may be transmitted from a computer system that stores the program in a memory device or the like to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. In addition, the above program may be for the purpose of realizing a part of the functions described above. Furthermore, it may be a so-called differential file (differential program) that can realize the functions described above in combination with a program already recorded in the computer system.

[0071] Although embodiments for carrying out the present invention have been described above using examples, the present invention is not limited in any way to these embodiments, and various modifications and substitutions can be made without departing from the spirit of the present invention. [Explanation of Symbols]

[0072] 1…Data transmission system, 2,2A…Control device, 3…Device, 4…Bus, 21…Transmitter, 22…Receiver, 23…First control unit, 24…Drive circuit, 25…Storage unit, 211,211A…Bus voltage control circuit, 221…Bus current monitoring circuit, 310…First device, 320…Second device, 311,321,...Functional unit, 312,322,...Second control unit, 313,323,...Variable current source, 314,324,...Receiver

Claims

1. A data transmission system that shares power supply and data transmission, The system comprises a first device and a second device, The first device comprises a voltage control means and a current monitoring means, The second device comprises a variable current source and a control unit, The first device transmits the change in the voltage value controlled by the voltage control means as data to the second device. The control unit of the second device transmits data to the first device based on the change in the current value altered by the variable current source. The first device detects and receives as data the change in the current value transmitted by the second device using the current monitoring means. Data transmission system.

2. The transmission from the first device to the second device is such that, during the period allocated for 1-bit transmission, the bus transmitting the data does not constantly become low due to changes in voltage value. The transmission from the second device to the first device is performed during a period when the bus transmitting data is not at a low level due to the change in the voltage value. The data transmission system according to claim 1.

3. The voltage value controlled by the voltage control means is the negation of RTI (Return to Zero inverted). The signal resulting from the current value changed by the variable current source is NRZ (Non Return to Zero). A data transmission system according to claim 1 or claim 2.

4. The voltage control means transmits the change in voltage value as data to the second device, with a first voltage value lower by a first predetermined value than the power supply voltage as the first level, and a second voltage value higher by a second predetermined value than the ground level as the second level. The data transmission system according to claim 1.

5. The variable current source transmits the change in current value as data to the first device, with a first current value that is a third predetermined value lower than the maximum current value as the first level, and a second current value that is a fourth predetermined value higher than the zero level as the second level. A data transmission system according to claim 1 or claim 4.

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