4.4.1 M2M_PS_MANUAL

This is a fully host-driven Power Save mode.

• The WINC sleeps when the host uses the m2m_wifi_request_sleep API. During this period, the host MCU can also sleep for extended durations.
• The WINC wakes up when the host MCU application requests services from the WINC by calling any host driver API function, for example, Wi-Fi or socket operation.

For an active Wi-Fi connection, the AP may exit the connection if the WINC is unavailable due to long sleep time. If connection is dropped, the WINC detects the disconnection on the next wake-up cycle and notifies the host to reconnect to the AP again. To maintain an active Wi-Fi connection for extended durations, the host MCU application must periodically wake up the WINC in order to send a keep-alive Wi-Fi frame to the AP. The host must carefully choose the sleep period to satisfy the tradeoff between keeping the Wi-Fi connection uninterrupted and minimizing the system power consumption.

This mode is useful for applications which send notifications very rarely due to a certain trigger. It also fits applications which periodically send notifications with a very long spacing between notifications. Careful power planning is required when using this mode. If the host MCU decides to sleep for a longer period, it may use M2M_PS_MANUAL or may power off the WINC¹. The advantage of this mode compared to powering off the WINC is that M2M_PS_MANUAL saves the time required for the WINC firmware to boot since the firmware is always loaded in the WINC memory. The real advantage and disadvantage depend on the nature of the application. In some applications, the sleep duration can be long enough to be a power-efficient decision to power off the WINC and then power it on again and reconnect to the AP when the host MCU wakes up. In other situations, a latency-sensitive application may choose to use M2M_PS_MANUAL to avoid the WINC firmware boot latency on the expense of slightly increased power consumption.

During the WINC Sleep mode, the WINC in M2M_PS_MANUAL mode saves more power than M2M_PS_DEEP_AUTOMATIC mode. In M2M_PS_MANUAL mode, the WINC skips beacon monitoring whereas in M2M_PS_DEEP_AUTOMATIC mode, it wakes up to receive beacons. The comparison also includes the effect of the host MCU sleep duration: if the host MCU sleeps for a longer period, the Wi-Fi connection may frequently drop and the power advantage of the M2M_PS_MANUAL mode is lost due to the power consumed in the Wi-Fi reconnection. In contrast, the M2M_PS_DEEP_AUTOMATIC mode can keep the Wi-Fi connection for long durations at the expense of waking up the WINC to monitor the AP beacon.