TS-7670 Sleep

The addition of a microcontroller on board this SBC allows it to play a supervisory role over the CPU. Two sleep modes are available, each with the ability to wake up after a set amount of time, or after a push of the tactile push switch on the edge of the PCB.

Sleep

This low power sleep mode will remove power from all of the rails, turning off the CPU and every other peripheral save for the microcontroller. This mode offers extreme power savings, only requiring around 9mW of power, with the ability to wake up after an arbitrary timeout (up to 1847297s, which is 21d 9h 8m 17s) with a 1s resolution. Note that as soon as the command to sleep is issued, the device will sleep as soon as possible. This has the ability to cause filesystem corruption if proper precautions are not taken before the SBC is put to sleep. In order to enter this mode, issue the following command:

tshwctl --sleep --timewkup <time in seconds> --resetswitchwkup

Note that both --timewkup and --resetswitchwkup are optional arguments, you can pass none, one, or both. If no arguments are passed then the SBC will remain in sleep mode forever, until power is removed completely and re-applied. This can be useful instead of halting in linux as sleeping would consume far less power than simply halting the CPU. Waking up from this mode will take roughly 4-5s from when the timer expires or when the reset button is pressed. This is normal bootup time for the CPU.

Standby

This sleep mode does consume more power, roughly 250mW, however the CPU is put in a standby mode with the RAM contents and CPU cache preserved. When the CPU wakes up from this mode it will continue execution from where it left off. This wakeup process takes roughly 250ms from when the sleep timer expires or the reset button is pushed. Like the sleep mode above, the timer on standby can be an arbitrary number (up to 1847297s, which is 21d 9h 8m 17s) with a 1s resolution. Unlike the above sleep mode, it is safe to enter standby at almost any time without concern for data loss. The only unsafe time is during a write to the SD card that has completed in linux, but the SD card controller is still attempting to flush the write to disk. In all of Technologic Systems' testing, we have not observed any corruption caused by entering or exiting the standby mode. The standby mode can be entered with the following command:

tshwctl --standby --timewkup <time in seconds> --resetswitchwkup

Note that both --timewkup and --resetswitchwkup are optional arguments, you can pass none, one, or both. If no arguments are passed then the SBC will remain in standby mode forever, until power is removed completely and re-applied. In the case of the standby mode however, it does not make sense to leave it in this mode indefinitely. After this mode is exited, the function of the reset switch is restored to its previous state, see External Reset for more information.