The continuous development of industrial control technology has led to increasingly higher requirements for industrial control systems in various application fields. Faster response speed, higher control accuracy, and better real-time performance are the constant demands of users and the goals that control system manufacturers are constantly pursuing. As a crucial component of the control system, the main function of the analog output controller is to receive command signals from PCs and various communication devices, obtain corresponding analog values ​​through internal logic algorithms and hardware circuits, and use these values ​​to control the opening of servo valves, thereby controlling the process operation status. The execution speed and output accuracy of the analog output controller are directly related to the control quality of the entire control system. Currently, analog output controllers are mainly implemented using microcontrollers and various dedicated chips/circuits, such as dedicated timers, D/A conversion circuits, and communication modules. However, due to the inherent shortcomings of microcontrollers, such as slow operating speed, weak data processing capabilities, and insufficient internal resources, the performance of analog output controllers obtained using microcontrollers is increasingly failing to meet requirements. To fundamentally solve this problem, this paper designs an analog output controller based on the TI TMS320F2801 DSP chip, combining the advantages of DSP's rich on-chip peripheral functions, pipelined structure, and efficient special instructions. A system scheme based on the analog output controller of TMS320F280x. Digital signal processing system is based on digital signal processing. Compared with general microprocessors, DSP has the following advantages: (1) Memory structure: DSP adopts Harvard structure, and the program and data memory are in two separate spaces. Therefore, instruction fetching and execution can be completely overlapped, further improving the running speed and flexibility. (2) Pipeline structure: The execution of instructions is decomposed into several stages such as instruction fetching, decoding, operand fetching and execution. During the program running process, different stages of different instructions overlap in time. The pipeline structure improves the overall speed of instruction execution. (3) Hardware multiplication and accumulation unit: DSP processor uses dedicated hardware to implement single-cycle multiplication and uses accumulator register to handle the accumulation of multiple products. At the same time, the DSP instruction set includes MAC instructions. (4) Zero-overhead loop: DSP has dedicated hardware to support loop structure, so that no time is spent on loop counting, conditional transfer and other loop mechanisms. (5) Special addressing mode: DSP supports special addressing mode, thereby reducing the processing time when encountering this part of the addressing mode. (6) High-efficiency special instructions: The DSP instruction set is designed with special DSP instructions for specialized digital signal processing operations. This improves the parallelism of instruction execution and speeds up the completion of this operation. (7) Abundant on-chip peripherals and peripherals: Depending on the application field, the DSP chip integrates various types of peripherals and peripherals. Abundant peripherals and peripherals improve processing speed and data throughput, simplify interface design, and reduce system power consumption and save circuit board space. The chip used in this design is the TMS 320F2801. The chip has 16kB of Flash and 12kB of SARAM. Due to the adoption of Harvard architecture, instruction pipeline operation, hardware multiplier/accumulator function and multiple addressing modes, the chip's operating speed is greatly increased. The chip provides a PLL phase-locked loop module to control the operating frequency of the DSP core, so that the execution speed of the chip core can reach 100Mb/s. At the same time, the TMS320F2801 provides abundant PWM resources, including 6 channels of EPWM waves and 2 channels of APMW waves, thereby realizing the analog output function of 8 channels of PWM. The hardware design and implementation of the analog output controller is shown in Figure 1. The system mainly consists of a DSP TMS320F2801, a PWM to D/A converter circuit, a self-test signal conversion circuit, a power supply circuit, a watchdog circuit, and a CAN receiver. Considering the interference of analog signals on digital signals, analog signals need to be isolated. Therefore, optocoupler circuits and high-precision linear optocoupler circuits are added to the hardware circuit to isolate the analog and digital signals. The working principle of the analog output controller is as follows: The controller receives output command signals from external devices (including PCs and various devices supporting communication protocols) via CAN communication. The DSP performs logic analysis and calculation to set 8-channel PWM output, and then obtains the analog output value required by the field signal through the PWM to D/A converter circuit. Simultaneously, the controller performs a self-test on the generated analog output value and transmits it to the DSP's A/D sampling channel through the self-test signal conversion circuit. This forms a closed-loop control, effectively controlling the analog output signal in real time. The TMS320F2801 is powered by two parts: a 1.8V core power supply and a 3.3V external core power supply. The chip has strict requirements for the power-on sequence, requiring the core to power on before or simultaneously with the external core. In this design, to meet the power-on requirements of the TMS320F2801, the TPS70151 dual power management chip with power-on sequence is selected. The TPS70151 chip has an input voltage of +5V and provides dual power outputs of 3.3V and 1.8V. Through the power management chip, the user can change the power-on sequence of the two power supplies by controlling the SEQ pin on the chip. In this design, the SEQ pin of the TPS70151 chip is pulled up, causing Vout2 (1.8V) to power on first, followed by Vout1 (3.3V), thus meeting the power-on sequence requirements of the DSP chip. The TMS320F2801 chip provides numerous peripheral functions to meet various user requirements. Six EPWM waveforms can be obtained by configuring the chip's internal Enhanced Pulse Width Modulation (EPWM) module. Simultaneously, the Enhanced Capture Module (APWM) can generate two APWM waveforms. Thus, the analog output controller can generate eight PWM output waveforms. In this design, an optocoupler chip completely isolates the digital and analog signals. The converted PWM waveform is then regulated by an RC filter and a current-series negative feedback circuit to maintain a constant current on the load. The PWM signal is regulated to an average voltage Vi after a two-stage RC filter. Vi then passes through a voltage follower circuit and a current-series negative feedback circuit to generate the final current output. The TMS320F2801 chip contains 35 GPIO lines, a large portion of which are multiplexed. The GPIO ports of the TMS320F2801 are unidirectional, meaning they can only be configured for digital input and output functions. This results in an insufficient number of GPIOs in practical applications, leading to significant design flaws. Therefore, this design compensates for the insufficient number of GPIOs by using external 74HC139, 74HC245, and 74HC574. The design of the self-test circuit is crucial because the analog output controller is the central component of the field loop; the magnitude and stability of the output current and voltage provided by the controller directly affect the operation of the field equipment. Therefore, the correctness and quality of the controller's output signal need to be monitored to form a closed-loop control loop. In this design, the external signal self-test is monitored through the built-in A/D channel of the TMS320F2801 chip. The controller's output signal is sampled back through a linear optocoupler to obtain a differential voltage consistent with the controller's output signal. This voltage is sampled through the chip's internal A/D channel, informing the controller's internal DSP processor of the correctness and magnitude of the current output signal. When a fault occurs in the output signal, the sampled value will also change, and the controller program will execute a preset fault handling procedure, informing the user of relevant alarm information and taking appropriate action. Software Design of the Seven Controllers 1. Overall Software Flow The software for the TMS320F2801 was written in the CCS (C2000) compilation and development environment. CCS (C2000) supports assembly language and C language, making it easy to port and highly readable. The software development of the analog output controller based on the DSP chip mainly includes four sub-modules: initialization module, communication module, PWM output control module, and self-test module. The software flow of the program is shown in Figure 2. After the controller is powered on, the controller initialization work is performed. After initialization is completed, the controller enters the main loop. The CAN communication program is an interrupt program. When an external device sends communication data, the analog output controller detects the generation of new CAN data, triggers the interrupt subroutine, and buffers the CAN data. The interrupt ends. The TMS320F2801 judges whether the communication data is correct and whether the data is consistent with the current output data. Based on the judgment result, the analog signal that matches the instruction information is obtained through the PWM circuit and D/A conversion circuit. After outputting the analog signal, the signal value of the field output terminal is collected by the self-test circuit to determine whether the output signal matches the command information issued by CAN, provide relevant diagnostic information and alarm information, and perform corresponding operations. 2. Initialization Module The initialization process of the controller mainly includes 5 parts: initialization of variables and registers, DSP initialization, cold and hot start judgment, hot start initialization, and watchdog initialization. The initialization process completes the setting of relevant parameters of the controller's internal hardware circuit and DSP chip. 3. CAN Communication Module The TMS320F2801 chip has rich peripheral communication interfaces, including CAN, SPI, I2C, and SCI. In this design, the analog output controller is connected to external devices through the CAN communication interface. For the analog output controller, as long as the device conforms to the CAN communication protocol, including various instruments and PCs with CAN drivers installed, it can control the magnitude of the output signal of the analog output controller and receive the alarm information of the controller. In the design of CAN communication, the following issues should be noted: (1) The internal registers of CAN are all 32 bits. Only 32-bit read/write can guarantee safety. 16-bit or single-bit read/write may corrupt the register contents. Therefore, register read/write should be set through a mapped register. (2) Before using the CAN module, initialization must be performed to set the baud rate and PWM cycle parameters. (3) Critical registers are protected by EALLOW to prevent accidental changes. For critical register operations, EALLOW and EDIS must be used correctly. (4) When configuring the receive mailbox message identifier MSGID, the flag extension bit IDE must be configured as needed (standard format is 11-bit identifier, extended format is 29-bit identifier), and the configuration differs between standard CAN mode and enhanced CAN mode. If receive mask is used, the receive mask enable (AME) bit must be set (MSGID.30=1). 4. PWM Output Control Module The PWM output control module is the most important part of the analog output controller software design. After the controller receives the output command information sent by the CAN channel, it converts it into an analog output signal through the PWM output control module. The PWM waveforms of the DSP chip are all obtained through internal timer settings, and the output accuracy of the PWM is related to the DSP chip's system clock. The relationship between the system clock, the PWM period, and the resolution of the D/A output is as follows: Resolution = Log2(TPWM/TSYSCLK). Where TPWM represents the PWM period time, and TSYSCLK represents the system clock. In this design, the PWM period TPWM is set to 819.2μs, and TSYSCLK is set to 0.02μs (50MHz). Combining the equation, the resolution can be calculated to be 15.3 bits. Since the design requires the controller's output accuracy to be 0.2%, the PWM resolution obtained under these conditions fully meets the design requirements. The PWM circuit integrated into the DSP hardware greatly reduces the CPU overhead for generating the PWM waveform. At the same time, the integrated design significantly reduces the user's workload. In conclusion, as computer hardware technology matures, the requirements for product circuit integration become increasingly stringent, and the demands for software portability and ease of operation become increasingly urgent. The rich peripheral functions of DSP chips, support for multiple languages ​​and operating systems, and the high integration and sophistication of software algorithms enable the chips to be applied to products in various industries. This paper presents an analog output controller designed using TI's TMS320F2801 as the core controller. Practical application has proven that the product's performance in all aspects far surpasses that of products designed based on microcontrollers. Due to the high integration, low cost, and ease of development of the TMS320F2801 chip, design time is significantly shortened, hardware and software costs are greatly reduced, and production and maintenance efficiency are improved. The design and development concept based on DSP chips can also be widely promoted and applied in other products with analog output functionality.