| .. | ||
| delays.c | ||
| delays.h | ||
| gpio.h | ||
| kernel8.img | ||
| link.ld | ||
| main.c | ||
| Makefile | ||
| mbox.c | ||
| mbox.h | ||
| OLVASSEL.md | ||
| power.c | ||
| power.h | ||
| README.md | ||
| start.S | ||
| uart.c | ||
| uart.h | ||
Tutorial 08 - Power management
For embedded systems, power consumption is critical. The Raspberry Pi 3 has a very sophisticated PM interface. You can turn each device on and off idependently. There's a catch though, the GPIO VCC pins are hardwired, there's no way to turn them off programatically. This means if you connect some devices to them, you'll have to implement a way to turn those devices off (with a transistor connected to a data GPIO pin for example).
Power.h, power.c
The power management controller is one of the peripherals that are not emulated properly by qemu. Works on real hardware though.
power_off() shutdowns the board to a almost zero power consumption state.
reset() reboots the machine. Also handled by the PMC, and since the Raspberry Pi does not have
a hardware reset button, it's very useful.
Main
We display a simple menu, and wait for user input. Depending on the input, we reboot the system or power it off.