The ultra-low power consumption microcontroller efm32 based on 32-bit Cortex-M3 core and the highly integrated tdc-gp21 chip of ACAM company have introduced the ultrasonic heat meter scheme, which can give full play to the characteristics of ultra-low power consumption and high computing power of efm32 and the high precision measurement ability of gp21. It will become the best choice in the ultrasonic heat meter scheme.

  Main control and display part

Efm32tg840f32 is adopted as the ultrasonic master control MCU. It is designed based on 32-bit Cortex-M3 core of arm company. Compared with traditional 8-bit and 16 bit MCU, it has higher computing and data processing capacity, higher code density and lower power consumption. The actual data shows that efm32tg840 only needs 4 core clock cycles to perform 32-bit multiplication, 8 core clock cycles to perform 32-bit division, and 50 and 465 clock cycles to perform 16 bit microcontroller on the corresponding heat meter. The data collected on tdc-gp21 is 32 bits in length, so it is 32 bits in calculation and heat calculation. It can be seen that using efm32tg840 can make the ultrasonic heat meter have better calculation performance, so that the whole machine can shorten the running calculation state, and achieve the effect of reducing the running power consumption.

Efm32tg840 has five low power consumption modes: em0-em4. In the low power consumption mode of em2, the microcontroller can still realize RTC operation, communication or control functions of leuart, letimer and lesense, and the power consumption is only 900 a. Moreover, it has a flexible wake-up mode and an autonomous PRS system, which can be wakened by external I / O, I2C communication interface, leuart communication signal, etc.

Efm32tg840 integrates 8 × The 20 Segment LCD driver can directly drive the LCD screen of ultrasonic heat meter, and the power consumption is only 550na. The LCD driver of efm32tg840 has integrated voltage boost function and contrast adjustment function, which can realize the VCMP voltage comparator in the chip to monitor VDD voltage, and turn on LCD boost and contrast adjustment by grades, so as to achieve good LCD effect, even if the system battery voltage drops with the increase of service time.

  Design of ultra low power ultrasonic heat meter circuit module based on gp21 + efm32

Figure 2 main control MCU and display circuit

The I / O of efm32tg840 can be set to low power consumption mode, wake-up mode and GPIO interrupt mode, so the external operation button can realize interactive control action under the condition of low power consumption.

Leave a Reply

Your email address will not be published. Required fields are marked *