All areas are competing for low power consumption to see how MCUs become the focus of low-power battles

Today, the development of science and technology, various handheld devices, wearable devices, energy applications are pursuing low power consumption, especially in the semiconductor industry. Low power consumption has been the focus of competition among major MCU vendors.

Before the development over 24h Holter recorder, the ECG acquisition section 17 # built batteries, the peripheral has no backlight 128 * 64 dot matrix LCD, SD card, a digital clock, multiple operation keys, LED indication, a buzzer, , external expansion 2Mbit RAM and the like, designed from the beginning to the collector positioned 48h of continuous work at a sampling rate of 250Hz or more conditions in the SD card, the sampling rate of 125Hz, the working time of up to 72h ECG data storage. Other functional requirements are not described one by one.

Previous low-power device development has been using T 's MCUs , including Flash -type MCUs and later FR (Iron-Electric Storage) series, until a coincidental seminar brought me to Silicon Labs (also known as " core technology " after) the launch of EFM32 MCU series, I see the outstanding advantages EFM32 meeting, had applied for a EFM32STK3600 by application platform development kit, which is the main EFM32LG990F256 Leopard Gecko MCU series CortexM3 kernel.

In order to compare the low power consumption characteristics of T company MCU and EFM32 , I run the code on two platforms separately. Because EFM32 internal RAM is large, there is no need to expand 2Mbit RAM . When testing the code, I use the general program to compare.

Test conditions: Use the same ammeter and measure the load at room temperature. T company MCU is divided into 6 operating modes, including 5 low power modes, AM (operating mode), LPM0~LPM4 ; EFM32 is divided into 5 operating modes, 4 low power modes, EM0 (operating mode), EM1~EM4 .

The datasheet description, EFM32 mode of EM2, EM3 mode wake-up time just 2uS, even the depth mode EM4 also just 160uS.

Through the above comparison, it is found that EFM32 does have lower power consumption, but the T company MCU in the AM mode, when the watch crystal is turned on, so the power consumption is slightly larger, the theory should be lower.

Later I ran FatFs file system using hardware SPI port driver SD card 2.0, running FatFs file system uses the SDIO driver SD card 2.0 on EFM32LG990F256, then has to write data to the card, the same capacity of 7 # battery on T's MCU, T The company MCU records longer data than EFM32 . This result seems to be contrary to the above measurement results. Later, the check program found that the T company MCU uses the hardware SPI port. At that time, the maximum port rate is 16M/S , and each time the card is written. After entering the LPM3 mode, the EFM32 uses the 32Mhz clock source at the time, the SDIO port rate is 32Mhz , and the EM0 mode is maintained after each write ; the clock rate is reduced to 16Mhz later , and the condition is consistent with the T company MCU . More significant than last time.

Therefore, the preliminary conclusion drawn later is that in the Flash type MCU , the low power consumption of the EFM32 series is more extreme and lower than that of the T company's Flash MCU . With the innovation of technology, some MCU designs have begun to use ferroelectric memory instead of flash memory to further reduce power consumption. It is expected that EFM32 will introduce a microprocessor of ferroelectric memory series.

In actual operation by means of the simplicity studio energyAware Profiler and Advanced Energy Management Module (AEM) function, provides an optimized way for code optimization; especially for systemic application development, by means of the simplicity studio AEM function code blocks can be divided according to The power consumption test finds the redundant part of the code execution, and then optimizes the details. The optimized code is checked again by AEM test. In this way, the power consumption of the embedded code will be the lowest. At the time, the migration of the FatFs file system on the EFM32 was optimized using the AEM energy monitoring function.

Simplicity Studio 's AEM capabilities are not available in other software in the industry. This feature can help developers solve power control problems. If you haven't used this feature yet, take the time to try it out.

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