ads1115 startread callback function is not optional

[athompson673]

Setting an interrupt on the alert pin with an appropriate callback function, and calling startread() with no callback results in an error.

> adc:startread()
Lua error:  stdin:1: bad argument #1 to 'startread' (Must be function)

This is contrary to the docs.. Was this a regression, or was this simply never an option?

[vsky279]

Hi, does the example in https://nodemcu.readthedocs.io/en/dev/modules/ads1115/#ads1115devicestartread work for you?