The openlabs 802.15.4 radio will not initialize with my nucleo-f401 and f411 boards.
Because the F411 board only was recently added to RIOT, a wasn't able to test this board with an older release of RIOT, so I switched to the F401.

The program does not get farther than the while statement in the _set_state function of st86rf2xx_getset.c:

if (state != AT86RF2XX_STATE_RX_AACK_ON) {
    while (at86rf2xx_get_status(dev) != state);
}

So I connected a scope to the SPI bus to check the signal levels and there comes the second problem:
In the current master branch, there is no signal on the SCK line.
For the next step, I switched back to the 2016.10 release of RIOT, because I heard, that there were some big changes in the SPI library recently. With this RIOT version, there is a clock signal, but still no proper initialization of the radio. The code was still stuck at the line mentioned above.

If it helps, I attached a photo of the SPI signal with working clock (2016.10 branch):

This gets send over and over again.