TS-7970 Silabs Sleep Mode

The TS-7970 implements a very low power sleep mode using the onboard supervisory microcontroller. This allows powering off the i.MX6 CPU entirely. While in this mode the entire board will consume about 3 mW.

The board can wake 3 ways:

• Timer - sleep mode requires specifying an amount of seconds to sleep (up to 16777215).
• SW1 - Pressing the button on the side of the board.
• PUSH_SW# goes low on HD1. The SW1 signal is brought to the header so connected cards can wake the TS-7970.

The sleep mode can be entered by calling 'tshwctl --sleep 60' to sleep for 60 seconds, but this typically should not be called directly. This would be equivalent to disconnecting power while booted which can cause data loss.

The Yocto, Debian, or Ubuntu distributions use systemd to manage shutdown. When systemd shuts down it will call all executables in the "/lib/systemd/system-shutdown/". Create a script with the name of "silabs-sleep" in said directory with these contents:

#!/bin/bash

tsmicroctl --sleep 60

And make it executable:

chmod a+x /lib/systemd/system-shutdown/silabs-sleep

Now the board will sleep immediately following a shutdown. It is safe during the sleep mode to disconnect power.