I think the heltec module is just a bit wonky.
I've now tried it with a Spark Core and it works there just like with the Arduino out of the box.
Someone on the Spark forums only got theirs only to work by adding the pull-up resistors.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I think the heltec module is just a bit wonky.
I've now tried it with a Spark Core and it works there just like with the Arduino out of the box.
Someone on the Spark forums only got theirs only to work by adding the pull-up resistors.