Alert and Interrupt events about pigpio

[fivdi]

A section was added to the documentation to describe the difference between interrupts and alerts. See here.

[fivdi]

Whats the difference between the interrupt and alert?

There's actually quite a big difference but it may not be immediately obvious. Take a look at the documentation for the pigpio C library gpioSetAlertFunc and the pigpio C library gpioSetISRFunc.

gpioSetAlertFunc is used for alerts. It provides information about state changes once per millisecond so there's quite a bit of latency. However, it provides very accurate tick information and can detect a lot more state changes per second than gpioSetAlertFunc.

gpioSetISRFunc is used for interrupts. It provides information about state changes as quickly as possible so there's a lot less latency than with gpioSetAlertFunc. However, the tick information it provides is not as accurate as the tick information provided by gpioSetAlertFunc. In addition, gpioSetISRFunc can't detect as many state changes per second as gpioSetAlertFunc.

What's the reason to not pass this tick along?

The pigpio Node.js module doesn't provide tick information for interrupts because I decided that it's not accurate enough.

[depuits]

Thanks, this answers my question. The latency is indeed described in the C library documentation but its easy to read over. Maybe this could be added to the documentation here to make the difference more clear in this library, because I thought I needed the interrupt til I couldn't find the tick in the interrupt event.

[fivdi]

@depuits Thanks for the feedback. Adding a note to the documentation makes sense. I'll add one.