![]() It will communicate with the main loop by updating shared data to indicate It ready for the next interrupt to occur. Typically an ISR will deal with the hardware device which caused the interrupt, making Has to be done immediately after the event which caused it: operations which can be deferred should be delegated Simplicity ¶įor a variety of reasons it is important to keep ISR code as short and simple as possible. Replace the original one - even if the second exception is cleanly handled. Thrown during the handling of an exception while the heap is locked, that second exception’s stack trace will The emergency exception buffer can only hold one exception stack trace. Debugging is simplified if the following code is included in any program using interrupts. If an error occurs in an ISR, MicroPython is unable to produce an error report unless a special buffer is createdįor the purpose. MicroPython issues ¶ The emergency exception buffer ¶ The data in the main program and re-enabling them immediately afterwards (see Critical Sections).Īllocate an emergency exception buffer (see below). Where data is shared between the main program and an ISR, consider disabling interrupts prior to accessing Shared between an ISR and the main program consider an array ( array.array). Where an ISR returns multiple bytes use a pre-allocated bytearray. Keep the code as short and simple as possible.Īvoid memory allocation: no appending to lists or insertion into dictionaries, no floating point.Ĭonsider using micropython.schedule to work around the above constraint. This summarises the points detailed below and lists the principal recommendations for interrupt handler code. The nature of the main program, and the presence of other concurrent events. Acceptable durations for an ISR are dependent on the rate at which interrupts occur, This is deliberate, as speeds areĪpplication dependent. This introduction uses vague terms like “slow” or “as fast as possible”. ![]() The language specific issues first, followed by a brief introduction to real time programming for those new to it. Others are common to all systems capable of responding to real time events. ![]() This carries significant consequences, some specific to the MicroPython In response to an event such as a timer trigger or a voltage change on a pin. also known as interrupt service routines (ISR’s) - are defined as callback functions. ![]() On suitable hardware MicroPython offers the ability to write interrupt handlers in Python. ![]()
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