1. Introduction In recent years, Digital Signal Processors (DSPs) have experienced rapid development, with continuously improving cost-effectiveness. They are widely used in various fields, such as communication, voice processing, image processing, pattern recognition, and industrial control, and are increasingly demonstrating significant advantages. DSPs utilize specialized or general-purpose digital signal processing circuits to process signals using digital computation methods. They feature high processing speed, flexibility, accuracy, strong anti-interference capabilities, small size, and high reliability, meeting the requirements for fast, accurate, and real-time signal processing and control. The paper uses the T1MS320F240 DSP as the core to design a high-precision inertial navigation accelerometer temperature control system . 2 Basic characteristics of the TMS320F240 series The TMS320F240 integrates the high-speed computing power and efficient control capabilities of the DSP. Its main features are as follows: (1) The core CPU includes a 32-bit central arithmetic logic unit (CALU), a 32-bit accumulator, a 16-bit × 16-bit parallel multiplier, 3 scaling shift registers and 8 16-bit auxiliary registers. The instruction cycle is 50 ns (20 MI/s), and most instructions are single-cycle instructions; (2) It has 544 B x 16-bit data/program RAM and 16 KB x 16-bit mask ROM or Flash EEPROM on-chip. The external memory interface has a 16-bit address bus and a 16-bit data bus. The maximum addressable register space is 224 KB x 16-bit. (3) The dual 10-bit analog-to-digital converter can realize simultaneous sampling of dual signals, and the conversion time can be programmed as needed. The shortest conversion time is 6.1 1J,s; (4) 6 external interrupts, including power drive protection interrupt, reset, non-maskable interrupt NMI and 3 maskable interrupts. 3 Hardware design of temperature control system The temperature controller based on DSP utilizes the powerful high-speed computing power of DSP, as well as its rich on-chip integrated control peripheral components and circuits, thereby simplifying the hardware design of the circuit. It can realize various control algorithms and control strategies, and read the data required by the user through the asynchronous serial communication interface, which is convenient for the user to analyze the experimental results. In addition, it also has a high temperature hardware protection function that is independent of DSP. It can eliminate the danger of system over-temperature caused by the accidental loss of control of DSP system, and improve the reliability and safety of the temperature control system. The system structure is shown in Figure 1. 3.1 Signal acquisition and amplification circuit The signal acquisition circuit is an important part of the temperature control system. Its accuracy of temperature measurement directly affects the accuracy of the entire temperature control system. Therefore, this system selects the stable PT1000 platinum resistance thermometer as the sensitive element for measuring temperature signals. Its resistance changes with temperature as follows: 1000Ω at 0℃, with a temperature coefficient of 3.84Ω℃. The linearity is less than 0.5%. The signal acquisition circuit uses a symmetrical differential bridge to measure the temperature signal. The platinum resistance thermometer Rt and precision resistors R1, R2, and R3 form the measurement bridge. X detection is the input signal for the hardware protection circuit. The temperature signal acquisition and amplification circuit is shown in Figure 2. To improve the system's acquisition accuracy, the bridge is powered by a high-precision reference voltage source AD586 from Analog Devices, and a current-limiting resistor RO is added before the bridge to ensure that the current flowing through the platinum resistance thermometer Rt is less than 10 mA. This minimizes the impact of the platinum resistance thermometer's own thermal effect on temperature acquisition. When the temperature changes, the resistance of the platinum resistance thermometer Rt also changes. The bridge output signal is amplified by an operational amplifier and then subjected to appropriate bias processing to ensure that its voltage meets the input voltage range of 0V-5V for the DSP's on-chip AID converter, thus enabling AID conversion. 3.2 External Memory Expansion During temperature control, a large amount of data needs to be acquired and processed. The inherent on-chip data memory space of the TMS320F240 is clearly insufficient. Moreover, if external memory is available during system debugging, the program only needs to be downloaded to the external memory through the simulation interface without needing to be burned back to the on-chip Rash. This simplifies program debugging. Therefore, the IS61C6416 static memory manufactured by ISSI is selected to expand the external memory. The IS61C6416 is a 64K x 16bit static memory manufactured using CMOS technology. It uses a 44-pin surface mount package, operates on a 5.0V power supply, and its input/output levels are compatible with TTL levels. It also features high-speed read/write access time and low-power operation. Table 1 shows the truth table of the IS61C6416's operating modes. The interface circuit between the IS61C6416 and the TMS320F240 is very simple; its 16 data lines and 16 address lines can be directly connected to the TMS320F240. As shown in Table 1, the IS61C6416 operates using five control signal lines. The enable pin and read/write select pin are connected to the DSP to control its read/write operations. Since the TMS320F240 series DSP is a 16-bit microprocessor, data reading and writing do not need to be separated; therefore, the high-order and low-order byte enable pins are directly grounded. 3.3 Serial Communication Interface Design The TMS320F240's Serial Communication Interface (SCI) is its internal programmable asynchronous serial communication module. It is a standard asynchronous serial digital communication interface, capable of half-duplex or full-duplex communication and communication between multiple machines. The SCI module is an 8-bit on-chip peripheral that communicates with external devices through the lower 8 bits of the DSP's 16-bit external data bus. It has independent transmitters and receivers. Both the transmitter and receiver are double-buffered and have independent enable and interrupt bits. The communication transmission rate, i.e., the baud rate, can be determined by programming the two 16-bit baud rate selection registers of the SCI. The SCI serial communication bus interface circuit is shown in Figure 3. Its interface circuit is relatively simple, mainly composed of Maxim's MAX232A and some peripheral components. SCIRXD and SCITXD are connected to the output and input pins of the SCI serial communication module of the DSP controller, respectively. RXD and TXD are connected to terminals 2 and 3 of the RS-232 standard interface on the circuit board, respectively. Resistors R2 and R3 and capacitors C6 and C7 are used as anti-interference components. Using this serial communication bus, asynchronous data communication between the DSP-based temperature control system and the computer can be realized, allowing the computer to read the data in the DSP memory in real time, which is convenient for system debugging and experimental result analysis. 3.4 High Temperature Protection Circuit Under normal circumstances, the operating temperature of the accelerometer should not exceed 90℃. Excessive temperature will burn out the accelerometer and cause the entire temperature control system to malfunction. In order to avoid the accelerometer temperature from being too high due to abnormal system circuit, the author designed a high temperature hardware protection circuit independent of the DSP, with a protection temperature of 85℃. The working principle of this circuit is as follows: When the temperature of the three accelerometers does not exceed the protection temperature point, the voltage signals detected by X, Y, and Z are greater than -4.5 V, the Zener diodes K1, K2, and K3 are not reverse-biased, the protection circuit does not work, and the entire temperature control system is in normal working condition. Conversely, when the temperature of any one of the accelerometers exceeds the high-temperature protection temperature point of 85℃, one of the detected voltage signals will be less than or equal to -4.5 V, and the corresponding Zener diode will break down in reverse, causing transistor Q1 to not conduct. The input of the 6N137 optocoupler will be high and the output will be low, transistor O2 will not conduct, and the four transistors Q3, Q4, O5, and O6 in the subsequent stage will all conduct, causing the four-channel power amplifier circuit in the subsequent stage to not work. This cuts off the power supply to the four heating elements, thus protecting the accelerometers. 3.5 Opto-isolation and Power Amplification: The temperature signal of the accelerometer is acquired and amplified by the acquisition circuit and then directly sent to the DSP's MD converter for A/D conversion. The converted digital signal is processed by the DSP, and a PWM pulse width modulation signal is output from the DSP's PWM/CMP pin. This control signal is isolated by a 6N137 optocoupler and controls the operation of the power amplifier circuit, thereby controlling the working state of the heating element. The power amplifier circuit consists of switching transistors Q1 and Q2, with a gain of approximately 2000. X is the output signal of the protection circuit. The circuit is shown in Figure 5. 3.6 JTAG Standard Emulation Interface Design Like all microprocessors, DSP development also requires a complete set of hardware and software development tools. The author selected the TDS510 uSB interface emulator developed by Beijing Wenting Company. Its emulation signal line adopts the JTAG standard IEEE 1149.1 and uses a 14-pin standard emulation connector. The distance between the DSP target system and the emulator is less than 152-4 mm (6 inches), so a simple unbuffered connection is used. Among them, EMU0 and EMU1 must be connected to a pull-up resistor (generally 4.7kΩ) to make the signal rise time less than 10μs. The simulator only participates in data transmission, downloading the target code from the computer to the target system's memory via the JTAG interface. Simulation is performed within the DSP. Therefore, the JTAG standard simulation interface is a necessary communication interface between the simulator and the DSP target system, facilitating simulation and debugging of the DSP target system. During system debugging, the compiled program code can be downloaded to an externally extended program memory through this simulation interface, allowing online debugging of user programs and viewing of memory, CPU registers, various graphs, etc. After successful system debugging, the debugged program can be burned into the DSP's Flash memory via this simulation interface, making the DSP target system an independently runnable system and making DSP development more convenient. 4. Experimental Testing Using the above-mentioned DSP-based temperature control system, along with a quartz flexible accelerometer assembly and a heating element, and utilizing Wenting's 2000 series DS/C/C2000 simulation debugging software, an incremental proportional-integral-derivative (PID) control algorithm was employed. Extensive simulation experiments were conducted on the system through the simulation interface. The experiments demonstrated that the DSP-based accelerometer temperature control system can achieve good control effects. 5. Conclusion The DSP-based temperature control system, with a high-speed DSP as its core and supplemented by corresponding peripheral circuits, can achieve complex control and is currently used in a navigation testing system. Practical application shows that this control system has good control performance, meets the system's accuracy requirements, and has certain application value. Editor: He Shiping