Accelerometer gyrometer for radxa board - i2c configurable addresses vs spi
To answer my own question, as someone might do the same mistakes:
 1. i2cdetect -y -r 0, only 0 is for "public" devices. -r outprints the results you want to have
 2. Radxa needs 3V connected to Vin and Vdd 
 3. I2c is maybe fast enough,if you use the kernel (see https://stackoverflow.com/questions/27451233/i2c-set-clock-freq-radxa-rock-pro)