It looks like D28 and D29 are already used for SPI for the onboard sensors: http://www.espruino.com/modules/Ruuvitag.js
So setting them to I2C is likely to mess things up. Are there any other pins you think you could get to?
@Gordon started
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.
It looks like D28 and D29 are already used for SPI for the onboard sensors: http://www.espruino.com/modules/Ruuvitag.js
So setting them to I2C is likely to mess things up. Are there any other pins you think you could get to?