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How does the MCU turn off the GPIO?
When the MCU is ready it can drive the GPIO low which will then turn off the circuit. This is a soft power switch that wakes up the device that is in sleep mode. So instead of the switch disrupting the current path it the MCU is in a low powered state till told to wake up.
How does the MCU work when power off?
The MCU can also be placed into a safe state before power off as well to preserve data. When a user presses the switch the MCU can see the state change on the switch through the GPIO pin and initiate shutdown. When the MCU is ready it can drive the GPIO low which will then turn off the circuit.
Can a RTC wake up a MCU from deep sleep?
Currently I have an RTC (DS1337) that wakes up my MCU (ATMEGA328P) from deep sleep via hardware interrupt. While the sleep current is fairly low ( avg 76 uA), it is still a fairly large amount if I aim for a device to run in the wild for couple of years.
How are panel mount switches used for power control?
Panel mount switches need wires to go from the switch to the PCB. These are switches that control the flow of electrons indirectly using relays, mosfets, or SSR (solid state relays). This works by using a smaller low power switch to turn on the relay, mosfet, or SSR which then turns on the more high power circuit.
Where can I find soft power control circuit?
This style of soft power control is typically found in Automotive and Industrial applications for high current and power requirements. This circuit has a switch that allows power to go to a relays coil, a mosfets gate, or a solid state relays input.
How are GPIO pins used in a microcontroller?
You can connect a bunch of them to one microcontroller interrupt then use the I2C (or another bus) to see which one is active. When a GPIO has high drive capability, it is just a push-pull pin that can source or sink more current than usual.
What happens to the input pin on a microcontroller?
If any of the open-drains are pulling the line to zero, the input will be zero. Since none are ever pushing, you won’t have any digital infighting (which is worse than floating pins).