This article presents the design of a multi-channel data acquisition and storage system that integrates the TMS320F2812 digital signal processor (DSP) with the ADS8365 analog-to-digital converter (ADC). The system is designed to support high-speed, synchronized sampling of multiple analog signals, making it suitable for applications such as industrial control, motor systems, and sensor-based monitoring.
The TMS320F2812 is a high-performance 32-bit fixed-point DSP from Texas Instruments, part of the C28x series. It features a clock speed of up to 150 MHz, along with various communication interfaces such as I2C, SPI, CAN, and PWM, which make it ideal for embedded control systems. The TL2812-EVM development board provides a convenient platform for testing and evaluating the TMS320F2812's capabilities. With its compact size and robust performance, the TMS320F2812 is well-suited for both industrial and portable applications, including those requiring operation in extreme environmental conditions.
The ADS8365 is a high-speed, low-power ADC capable of simultaneously sampling six channels at up to 5 MHz. It offers excellent common-mode rejection, with an 80 dB rejection ratio, and includes six differential sample-and-hold amplifiers. The device operates on a single +5V power supply and provides a 2.5V internal reference, making it highly versatile for various analog input ranges. Its high-speed parallel interface enables fast data transfer, essential for real-time data acquisition systems.
In this system, the TMS320F2812 communicates directly with the ADS8365 using a parallel interface. The ADS8365 supports direct address read, FIFO read, or cyclic read modes, and the system uses the direct address mode for simplicity and efficiency. The chip select (CS) pin controls the data bus state, while the XA[2:0] pins serve as the lower address lines for accessing the conversion result registers. When CS is low, the ADC outputs the current data on the parallel port.
To achieve synchronized sampling across all six channels, the TMS320F2812's GPIOB14 pin is connected to the HOLDA, HOLDB, and HOLDC signals of the ADS8365. This ensures that all ADC channels are sampled at the same time. Additionally, the EOC (End of Conversion) signal from the ADS8365 is connected to the XINT1 interrupt pin of the TMS320F2812, allowing the system to trigger an interrupt once the conversion is complete.
For multi-channel expansion, the system uses the lower address lines of the TMS320F2812 to address multiple ADS8365 chips. The CLK and HOLDX signals are shared among the ADCs, simplifying the overall design. To accommodate the ±5V output from the sensors, a preamplification circuit using the OPA227 operational amplifier is implemented. This circuit adjusts the signal level to match the ±2.5V input range of the ADS8365, ensuring accurate and reliable data acquisition.
The software design of the system is based on the C programming language, taking advantage of the TMS320F2812’s powerful development environment. The program initializes the system, configures the necessary peripherals, and sets up the interrupt handling mechanism. Upon power-up, the system resets the ADS8365, initializes the TMS320F2812, and configures the GPIO ports and ADC settings. Once ready, the system starts the T1PWM signal to drive the ADC clock and waits for the EOC interrupt to trigger the data reading process.
The system successfully addresses the challenge of synchronous sampling in complex applications such as brushless doubly-fed motor control. By enabling precise and real-time data acquisition, this design is applicable to a wide range of fields, including motor control, multi-axis positioning, and high-precision data acquisition systems. It demonstrates the effectiveness of combining the TMS320F2812 and ADS8365 in achieving high-performance, real-time data processing solutions.
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