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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.
@DrAzzy
The MCU internal pullups are not nearly as strong as is specified by the I2C spec. (The same is true on Arduino - it's not as far off, but it's still out of spec).
You might be able to get the desired behavior by setting the appropriate registers with poke - but as I said above, I don't expect it would work.
I always use external pullups when working with I2C.