Waking the Raspberry Pi with a wireless command

Dietmar Hoepfl, 123RF.com

Remote Activation

If you want to power your Pi solely with batteries, then it makes sense for the Pi to only be turned on when you need it. The Pi can boot when called remotely via radio signal sent over the European 868 MHz band.

The "Witty Pi" board manufactured by UU Gear in 2015 provided a handy solution for booting a Rasberry Pi at a predetermined time [1]. This solution can be expanded to accommodate as many events as desired since the onboard RTC (Real Time Clock) chip has a central feed point for additional hardware trigger signals. This article expands on this model in the form of a radio module which initiates the boot process upon receiving a pre-defined wireless signal.

In order for the extension to work, the device that you want to start should only react to a radio frequency identification (RFID) that has been individually assigned. In this way, it is possible to control several distributed systems separately. Acknowledgment of system status by sending a corresponding return signal datagram should also occur when a Pi has already been started.

The low priced FSK-wireless modem module RFM69 [2] can be used for this project. It contains a transceiver chip SX1231 [3] and all of the other necessary components. The only thing that needs to be added before the elements can be integrated into the Raspberry Pi circuitry is an antenna. I built one of these himself from standard components found in a building supply store (Figure 1). It is made of insulated cable,1.5 mm2 in diameter. The thickness makes for greater stability and bandwidth. The length of the cable does not need to be milimetrically precise. The SPI Bus on the Pi controls the transceiver component and switches it between receiving and sending mode.


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