Abstract: Stepper motors can be directly controlled by pulse signals, making them suitable for digital control systems. Based on this characteristic, a stepper motor control system scheme using a TMS320L F2407A digital signal processor with an embedded CAN controller is proposed. The system structure, hardware block diagram, and CAN interface circuit design of this scheme are presented. The hardware system of this scheme has a compact structure, reliable performance, and high anti-interference capability of the information transmission channel. Keywords: DSP; TMS320L F2407A; CAN; sampling; stepper motor. A stepper motor is an actuator that converts electrical pulses into angular displacement. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (i.e., step angle) in a set direction. The stepper motor controls the angular displacement by controlling the number of pulses, thereby achieving accurate positioning; simultaneously, it controls the speed and acceleration of the motor by controlling the pulse frequency, thereby achieving speed regulation. As a control actuator, the stepper motor is one of the key products in mechatronics and is widely used in various automated control systems and precision machinery. With the continuous development of power electronics, microelectronics, and control technologies, various novel stepper motor drive technologies have been proposed to improve the overall performance of stepper motors. The development of stepper motor drive technology has also promoted the continuous expansion of the application range of stepper motors. Digital signal processors (DSPs), which emerged in the early 1980s, not only enhanced the data processing capabilities and improved the accuracy of microprocessors, but also integrated a large number of peripheral interfaces on-chip, thus finding widespread application in control systems [sup][1] [/sup]. This system selects a high-speed, powerful digital signal processor as the controller. 1. System Structure The stepper motor control system based on DSP and CAN bus consists of a stepper motor, a microcontroller, a CAN bus, and an industrial computer. Its system structure is shown in Figure 1. The industrial computer is the core of the control system, responsible for the control and management of the entire system. It mainly sets the parameters of the control modules through the fieldbus network, acquires data and information from the control modules in real time, and performs functions such as display, data analysis, and report generation. The CAN bus part mainly consists of a CAN bus adapter card, communication medium, and corresponding software, mainly responsible for the transmission of digital signals. The microcontroller is used to receive commands from the main controller, complete the control of the stepper motor, and send motor operating status information to the main controller. 2. Hardware Design The hardware design of the system mainly consists of opto-isolation and drive parts, power supply parts, and CAN communication parts. The opto-isolation and drive parts are the core parts for controlling the stepper motor operation; the CAN communication part mainly involves the interface circuit design between the CAN controller and the microcontroller. The system hardware block diagram is shown in Figure 2. 2.1 Main Features of TMS320L F2407A The TMS320L F2407A chip, manufactured by Texas Instruments, integrates real-time signal processing capabilities and controller peripheral functions, making it particularly suitable for industrial control applications. Its core uses a Harvard architecture, offering high processing speeds up to 40 MIPS. It features abundant general-purpose input/output pins. The chip operates on a 3.3V supply voltage, reducing controller power consumption; it has 16 10-bit ADCs and 8 PWM channels; and it also provides a CAN communication module compliant with the CAN 2.0B specification. It boasts advantages such as low cost, low power consumption, high-speed processing, and high-performance processing capabilities, thus meeting the requirements of this system. [sup][2] [/sup]. 2.2 Opto-isolation and Power Drive Section The power drive circuit amplifies the pulse signal, providing sufficient current to the stepper motor windings to drive the stepper motor normally. The requirements for the power amplifier include: providing sufficient amplitude and steep excitation current; low power consumption and high efficiency; stable and reliable operation; easy maintenance; and low cost. In power conversion circuits, due to the need for circuit topology and the requirement to improve circuit anti-interference capability, it is necessary to achieve electrical signal isolation between the power main circuit and the control circuit. The performance of the isolation link directly affects the operation of power devices and the anti-interference capability of the entire circuit system. This drive system uses the IR2110 driver produced by IR Corporation of the United States [3]. It has the advantages of optocoupler isolation (small size) and electromagnetic isolation (high speed), and is the preferred type of drive device in small and medium power conversion devices. In particular, the successful design of high-end floating bootstrap power supply can greatly reduce the number of drive power supplies. For three-phase bridge converters, only one power supply is needed. The circuit of IR2110 used to drive half bridge is shown in Figure 3. 2.3 Communication circuit design In this design scheme, CAN bus technology is adopted. This bus technology has a unique mechanism, and its main advantages are as follows: network nodes are not distinguished as active master and slave; non-destructive bus arbitration is adopted to support competition; long transmission distance and high communication speed (maximum 1Mbit/s). Flexible networking; its messages adopt a short frame structure, short transmission time, low interference, and have its own protocol, so the fieldbus CAN effectively supports distributed control systems or becomes a serial communication network for real-time control due to its own advantages. The TMS320L F2407A has a built-in CAN controller, which simplifies the peripheral design of the entire circuit and improves reliability. Considering the high data transmission speed and anti-interference of the CAN bus, the CAN communication scheme is designed in the following aspects: the CANRX and CANTX of the DSP are first matched with 3.3V and 5V through 74LVC04A, and then connected to TJA1050 through high-speed optical isolation TLP113 to achieve electrical isolation of the bus; TJA1050 is used as the driver to replace the previous 82C250. The advantages of TJA1050 are that it fully complies with the ISO 11898 standard; the high speed is up to 1 Mbit/s. Good electromagnetic interference resistance; unpowered nodes will not cause disturbance to the bus; output driver is temperature protected; at least 110 nodes can be connected. The digital power supply VCC and GND are obtained by first isolation using a low-power isolation module DC/DC, which increases the anti-interference capability of communication. The CAN communication interface circuit is shown in Figure 4. Angle 1.2°; Holding torque 28 N·m; Rotor inertia 33.97 kg·cm2; No-load operating frequency greater than or equal to 3 kHz. The voltage waveform is detected by a digital oscilloscope to obtain the current waveform (waveform after digital filtering). The phase current waveforms of the stepper motor during continuous operation and acceleration are shown in Figures 5 and 6, respectively. It can be seen from the current waveform that the phase current of the hybrid stepper motor maintains good sinusoidal characteristics at both low and high frequencies, indicating that the system has good dynamic and static performance. 4 Conclusion This paper applies DSP and CAN bus technologies to the control system of stepper motors, and elaborates on the isolation drive of stepper motors and CAN bus technology. The interface circuit design also makes full and ingenious use of the high integration and low power consumption characteristics of the DSP chip. It is not difficult to see that the system is flexible in control, reliable in data transmission, and has strong versatility and broad application prospects. The experimental results show that the system has good dynamic and static performance. References: [1] Zhou Mingan. Development and current status of stepper motor drive technology [J]. 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