Wake Up With SPI Communication Active

The simplest wake-up is using a SPI command to switch transceiver modes and SBC modes when the application requires the device to be awake. In general, the SPI bus is powered by a regulator that is internal to the SBC, which by default is going to be shut off during sleep mode to allow lower current consumption. However, many mid-range SBCs such as TCAN24xx-Q1 and TCAN28xx-Q1 have an option to turn on the SPI regulator (VCC1 in both devices) while the SBC is in sleep mode. This means that the SBC can be in a sleep state. If VCC1 is active that means the SPI bus is also active and the end user can send a SPI command to switch the SBC into different modes such as standby or normal modes. This allows the SBC to be woken up by the host controller through a simple SPI command. This does come at the cost of increased current usage during sleep due to the internal regulator being on and active.

That covers a simple wake up method for an SBC with the internal regulator turned on, but what about the transceiver? Since the transceiver state can be changed through a SPI command, a simple SPI command can be used to wake the transceiver as well. Check the device data sheet to verify if a specific SBC mode allows the end user to change the transceiver mode as well. If this is allowed and the SPI bus is active – a simple SPI command, such as an SBC mode switch, can be used as the only thing that changes is the register address and the data being written.

This largely covers the trivial forms of wake-up, but in many applications the SBC does not have the main regulator active so other wake methods must be considered.