M5Stack modules and Espruino

Thanks for the quick reply Gordon!
And yes, setup is done:

I2C1.setup({scl: D22, sda: D21, bitrate: 400000});
I2C1.writeTo(0x56, [0, 100, 0]);    // the 2 is not needed as it's the length of the data

Tried with [] and without, with 100 and 400 kbit/s

I cannot change the pins. I can see/detect the slave Mega328. I2C1 works for everything I throw at. I think I'm missing something to make the Lego+ module "start" somehow.
My hope is someone uses a M5Stack module and loves using Espruino on it too.