Low-level
SPM#
The SPM (Smart Power Management) is an embedded system that controls the low-level power cycle of the device. It interacts with a number of subsystems that can initiate power state changes:
| Subsystem | Description |
|---|---|
| Accelerometer | Built-in accelerometer is capable of triggering wake up based on physical movement events. |
| Modem | Installed modem module can trigger wake up on received SMS or dial up call. |
| STN | Built-in chipset triggers power on and off based on voltage level changes. |
Finally the Raspberry Pi communicates directly with the SPM and performs power state changes based on more high-level decisions.
States#
Below diagram shows an overview of all possible SPM states and the transitions between.
OFF#
Everything is powered off.
Transitions#
| State | Condition |
|---|---|
| BOOTING | The device is plugged in. |
| HIBERNATING | Maximum number of boot attempts reached. Default is 10 attempts. |
BOOTING#
Everything is powered on and the Raspberry Pi is booting up.
Transitions#
| State | Condition |
|---|---|
| ON | Successfully communicated with the Raspberry Pi. |
| OFF | No communication with the Raspberry Pi within a given time limit. Default boot timeout is 10 minutes. |
ON#
Everything is powered on and there is regular communication with the Raspberry Pi.
Transitions#
| State | Condition |
|---|---|
| SLEEPING | The Raspberry Pi decided to sleep for a given period of time. |
| HIBERNATING | The Raspberry Pi decided to hibernate or the STN chip powered off according to its triggers. |
| OFF | No communication with the Raspberry Pi within a given time limit. Default heartbeat timeout is 3 minutes. |
SLEEPING#
The Raspberry Pi is powered off. Modem and GPS is kept on in low power mode.
Wake up will happen after a specified period of sleep time or earlier if:
- STN is powered on.
- Received wake signal from modem.
- Received wake signal from accelerometer.
Transitions#
| State | Condition |
|---|---|
| BOOTING | See the above criteria. |
HIBERNATING#
Everything is shut down for maximum power saving.
Transitions#
| State | Condition |
|---|---|
| BOOTING | The STN powers on (when transitions from off to on). |
STN#
See the STN command for available power trigger options here.