Last week we released a new version of the Emcraft Embedded Linux distribution targeting the STM32F7 system-on-module (SOM-STM32F7). This release adds support for Linux low power mode, also known as the "Linux suspend to RAM" functionality. The main idea is that Linux running on the STM32F7 can be put into a "suspended" (low-power) state by switching the external SDRAM to self-refresh mode. This cuts power to the Ethernet PHY and switches the STM32F7 into Stop mode. In this mode, the system sleeps and consumes less than 2 mA @ 3.3V. This can be compared to the 100-200 mA typically consumed by the SOM in normal operating mode. Linux provides instantaneous wake-up of the system to normal state on configured I/O events, such as GPIO triggers. This "suspend to RAM" functionality is advantageous in a wide range of power-sensitive applications. One typical use case scenario is a battery-powered installation that needs to sleep most of the time consuming as little power as possible while in suspend but still requires the full power of the Linux APIs to appropriately handle whatever I/O event has caused the system wake-up.

Refer to this application note for an introduction and demo of the "suspend to RAM" functionality. This note provides information on both theoretically calculated and practically measured power consumption of the STM32F7 SOM.

We will continue our efforts to improve support for Linux low-power operation, both by adding support for additional wake-up triggers and reducing the power consumption in suspend even further. We will keep you posted on our progress.

As usual, active customers are invited to download the new release here. The release notes provides a full list of the new capabilities available from this release.