Revealing the circuit design of DSP motor control serial communication system

In the motor control system, the client must set the operating parameters of the motor through the host computer, and the controlled motor must also transmit various operating status information to the remote control client in real time. Serial communication has low costs due to fewer connections. , simple, reliable and widely used. This article uses the SCI serial communication interface to realize the communication connection between the DSP controller and the PC; the motor control system must also have a digital display drive circuit so that the on-site controller can know the current speed of the motor and other information in a timely manner, so SPI is used to synchronize the serial It is necessary to realize the communication between DSP and peripheral devices. The serial peripheral interface SPI and serial communication interface SCI module of the digital signal processing chip TMS320LF2407A DSP are analyzed. In the motor control experimental system, a serial communication application example composed of these two modules is given. Focus on the related serial communication interface circuit hardware design.

Hardware circuit design of serial communication interface module

The operating parameters of the motor, such as steering, speed and position signals, are formulated by the host and transmitted to the DSP through RS232 serial communication. The DSP then returns the operating results to the motor control system of the host to realize the communication between the remote client and the controlled motor. communication between. Since the upper computer (PC) generally has an RS232 interface, we use the serial port of the upper computer and the asynchronous serial port SCI of the lower computer DSP to perform RS232C communication and data exchange to realize computer detection of controlled objects in industrial sites. and control. The serial communication interface circuit of TMS32OLF24O7A is shown in Figure 2. This circuit uses the driver chip ADM2O2E that complies with the RS232 standard for serial communication. The ADM2O2E chip has low power consumption, high integration, +5 V power supply, and 2 receiving and transmitting channels. Since TMS320LF2407A uses +3.3 V power supply, a level conversion circuit must be added between ADM202E and TMS320LF2407A. This article uses a diode (1N4oo7) and three resistors for level conversion.

Figure 2 Serial communication interface circuit

This experimental system uses the SCI serial communication interface circuit of DSP to realize the communication connection between the DSP controller and the host computer. The entire interface circuit is simple and highly reliable. The DSP controller uploads the real-time operating status of the control system to the host computer for storage and analysis through the SCI serial communication interface circuit, and the host computer transmits the control instructions (such as start, stop, forward rotation, etc.) through the SCI serial communication interface circuit. Reverse rotation, running speed, etc.) are sent to the DSP controller to achieve real-time control of the motor control system. The serial communication rate of this test system is variable, and the default baud rate is l 9200, which is adjustable from l200, 2400, 4800, 9 600, to l9 200.

Hardware connection circuit between SPI and MAX7219

The typical application circuit of MAX721 9 is shown in the figure. It is an 8-bit LED display driven by a single-chip MAX7219. Let the DSP work in the master operating mode through register settings, with the MAX7219 acting as a slave. The SPISIMO, SPISTE, and SPICLK of the 2407A DSP are connected to the DIN, CLK, and LOAD terminals of the MAX72l9 respectively. The DISP_l~DISP-8 of the MAX7219 is connected to the bit selection terminal of the 8 digital tubes, and the SEG-A~SEG-GP is connected to the 7-segment display segment driver. end and decimal point drive end. SPI provides a serial clock to the entire communication network through the SPICLK pin and controls the data transmission of the system; it provides a chip select signal to the MAX7219 through the SPISTE pin, which is active at low level; it outputs data to the DIN pin of the MAX7219 through the SPISIMO pin. Resistor R can change the brightness of the LED, and the driving peak current of each segment is about 100 times the current in R. The value of R cannot be less than 10 kl2. In actual use, you can first use an adjustable resistor to adjust the brightness, and then replace it with a fixed resistor of the same resistance when the requirements are met. It should be noted here that the normal operating range of the MAX7219 segment current is l0b40 mA. When the segment current exceeds 40 mA, an external current expansion circuit must be added.