2020-05-22 10:33:46, 修改于2020-05-22 11:38:10
Together with the NJU9103, NJRC has created a brand new analog front end (AFE) with built-in PGA that will be utilized to method analog signals that has a achieve of G-512. By combining the NJU9103 using an STM32F429 microcontroller from STMicroelectronics, a budget sensor sign processing technique can be assembled with relative simplicity. The arrangement works very like an oscilloscope, but can also output further information on the slew level, resolutions and precision on the NJU9103.
The NJU9103 is right for processing sensor alerts since it not simply provides a big measurement assortment but in addition has very compact dimensions (just 8 pins). Furthermore, it has a 16-bit-|¡è|2 A/D converter with sampling costs of 0.814ksps to 6.51ksps, by using a differential enter and optionally pseudo-differential input. Using an SPI interface, parameters could be altered easily by using a microcontroller. Sign examination and sign synthesis can be effortlessly done while using the corresponding analysis boards on the front stop and microcontroller and just a couple passive factors.
The evaluation package of your NJU9103 from NJRC was at first made for an STM32 NUCLEO-F411RE progress package. Even so, because of to the omission from the GUI NUCLEO board for looking through the Arduino interface, a Pc is required to show the measurement effects, hence the NUCLEO board was hence deliberately omitted to simplify the measuring program. To help a user-centric demonstration, the STM32F429 discovery board was utilized rather.
Technology of the sine wave signal
In this particular arrangement the STM32F429 generates a PWM signal which is related for the differential input on the NJU9103 by means of a single-pole low-pass filter in addition to a voltage divider. The electronic measurements are then despatched to your MCU by using the SPI interface and proven on the display. The combination of your demo boards - comprising the PGA, ADC, analog switch and calibration DAC - demonstrates the overall performance from the analog front conclude regarding resolution, precision, attain and velocity.
Configuration on the microcontroller
The MCU is configured utilizing the PC-based STM32CubeMX computer software, though the AFE is programmed together with the aid from the Keil MDK (Microcontroller Advancement Package) or Atollic TrueSTUDIO. Commands and information could be transmitted through SPI-BUS.
ST offers the software package required for this reason on its website (www.st.com). Rutronik also recommends that builders utilize the board help packages.
Interaction using the NJU9103 runs by way of the SPI1. The timer TIM3 generates the PWM signal, when TIM4 triggers the interrupt to display screen the measurements on the display screen.Order now an Analog Front End from Heisener. We work tirelessly to achieve fresh and ideas and bring something new to the table.Visit our website to learn more.
To make a precise PWM signal, the counters and prescalers in TIM3 should be outlined and set beforehand. The output is configured being a pull-up. The frequency of TIM3 is configured employing the APB1 (Advanced Peripheral Bus) clock sign. It ought to be observed that only the APB1 interface has the maximum clock frequency readily available for the timer TIM3.
To synthesize the sine wave sign, the PWM sign (obligation cycle) should be produced within an array. To filter or sleek the PWM signal, a low-pass first-order filter (1kOhm//1|¨¬F) using a 3dB issue at 1kHz is utilised. The ohmic voltage divider is often chosen while in the AFE determined by the selected obtain phases with the PGA. A sine wave sign is then despatched to your output. It ought to be famous in this article the most supply voltage of 1V should not be exceeded with the differential enter in the AFE.
Programming the NJU9103
At the time the demo board has long been configured with CubeMX, the SPI interface and exhibit are initialized, for which the board aid deal offers numerous practical features to facilitate operation.
When configuring the registers of the AFE by using the SPI interface, developers ought to heed a significant point in the info sheet, particularly that only bits 4 to seven could be outlined for your corresponding addresses in the registers, rather than all the byte as would typically be the situation. The registers is often initialized as described within the data sheet. Timer TIM4 is used to established the sampling frequency with the ADC. As per the Nyquist theorem, the sampling frequency relies to the signal frequency to be calculated. The sine wave sign may be visualized with all the support of the connected screen.
The mix with the two demo boards in this configuration is a perfect system to demonstrate the effectiveness from the new AFE from NJRC. This build also exhibits the various prospects provided for sensor sign processing inside the wide selection of purposes.