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SlashDevin / NeoSWSerial

Efficient alternative to SoftwareSerial with attachInterrupt for RX chars, simultaneous RX & TX
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Restructure interrupts to allow an external interrupt routine to call by pin #16

Closed SRGDamia1 closed 6 years ago

SRGDamia1 commented 6 years ago

To allow multiple types interrupts on the same vector

SlashDevin commented 6 years ago

This pull request added this capability. I see that the Readme does not describe the capability, so I need to update it. There's a good summary on the Arduino forum, here.

SRGDamia1 commented 6 years ago

Thank you! I guess I'm a little confused by how this would work. If I call the interrupt with Grey Gnome's Enable Interrupt, will NeoSWSerial take over the whole interrupt "vector" (ie, all 8 pins) or will it only grab the one Rx pin?

SlashDevin commented 6 years ago

EnableInterrupt is in charge of the ISRs (i.e., vector for the whole port) and dispatching to the registered functions.

NeoSWSerial::rxISR is simply one of the registered functions. NeoSWSerial will not define any ISRs when that define is uncommented. It's up to you (or one of your libraries) to call NeoSWSerial::rxISR when you know the pin has changed. You could simply poll the pin state, but that makes it susceptible to processing delays. However, this could cause NeoSWSerial to generate incorrect bits because the timings are off.

AltSoftSerial is better because it uses the Input Capture capabilites of the MCU. The MCU will save a timestamp of when the bit changed. This allows a little more flexibility in servicing the ISR. Even if the ISR is not called immediately, the timestamp will let AltSoftSerial know when the bit changed, not just that it changed sometime in the past.

SRGDamia1 commented 6 years ago

Ok, got it.

I know about AltSoftSerial and agree that it's more stable/accurate (and also doesn't have any ISR conflicts). But I also like that this gives the option of (almost) any pin, and it still seems a bit better than the standard SoftwareSerial.