A processor like the ESP8266 driving the \gls{WEMOS} D1 mini loses the content of its \gls{RAM} in deep sleep mode.
As a result, after waking up, the program itself is preserved, since it is stored in flash memory, but the program state is lost.
When there is a program state to be preserved, we must either store it elsewhere, limit us to light sleep, or use a microcontroller that keeps the \gls{RAM} intact during deep sleep.
-\todo[inline]{Na de voorgaande hoofdstukken kun je dit makkelijk expliciet maken voor mtask.
-For mTasks this implies that the mTask OS is preserved during deep sleep, but all shipped tasks and their states will be lost.}
+For mTasks this implies that the \gls{MTASK} \gls{RTS} is preserved during deep sleep, but all shipped tasks and their states are lost.
For edge devices executing a single task, explicit sleeping to save energy can be achieved without too much hassle.
This becomes much more challenging as soon as multiple independent tasks run on the same device.
On systems that lose the content of their \gls{RAM} it is not possible to go to deep sleep mode.
\section{Interrupts}\label{lst:interrupts}
-\todo[inline]{
-Ik zou hier een klein algemeen verhaal over interrupts schrijven om te zorgen dat de lezer weet waarom dit de moeite van het lezen waard is. B.v.
-An interrupt is a request for the processor to interrupt the currently exected code or its sleep, to handle the event. It is typically much more energy efficient and accurate when a sensor interrupts the processor to notify that something interresting is happening than when the processor repeatedly checks that sensor's state.
-}
Most microcontrollers have built-in support for processor interrupts.
-These interrupts are hard-wired signals that interrupts the normal flow of the program in order to execute a small piece of code, the \gls{ISR}.
+These interrupts are hard-wired signals that interrupts the normal flow of the program or sleep state in order to execute a small piece of code, the \gls{ISR}.
While the \glspl{ISR} look like regular functions, they do come with some limitations.
For example, they must be very short, in order not to miss future interrupts; can only do very limited \gls{IO}; cannot reliably check the clock; and they operate in their own stack, and thus communication must happen via global variables.
After the execution of the \gls{ISR}, the normal program flow is resumed.
repositories / phd-thesis.git / blobdiff