I guess i still continue this monologue
Problem solved. There is a line in src/bsp/platform/connectme/bsp.c which should setup the register with "current values", if I understood it correctly:
store->porta = narm_read_reg(NARM_PORTX_REG, NARM_PORTA_ADDR, data);
Anyway, even all of the GPIO pins were tied to pull-up, this didn't work
Commented it out and replaced with my own register initialization which drives all GPIO pins to "1" and changes modes to output and now it works as expected.