my radio module driver (work in progress) transmits Acknowledgement-Frames without forcing it to do anything. There must be a wrong condition (e.g. event or flags) in the interface between netdev2 and the hardware dependent part of the driver which forces the driver to fill the transmit buffer and send it.
Can anyone give me a hint where to search for the place where netdev2 is triggered to fill the tx-buffer and send the frame ( I guess an Ack-Frame)?
This are the first bytes inside my transmit buffer which were forced to be send:
my radio module driver (work in progress) transmits
Acknowledgement-Frames without forcing it to do anything.
Can you rephrase please? 802.15.4 ACK frames are generated by the hardware and not triggered by the network stack (they where sent by the radio after a valid 802.15.4 frame was received in which the ACK request bit is set). You can enable/disable this behaviour in the RXMCR register of the mrf24j40. The netdev2 provides an interface to set options (netopts). The NETOPT_AUTOACK option should be implemented by your driver to set this option on the device (didn't check your driver until now).
a wrong condition (e.g. event or flags) in the interface between netdev2
and the hardware dependent part of the driver which forces the driver to
fill the transmit buffer and send it.
Which application code did you use? Some time ago you wondered about additional packets sent by layer 3. When exactly do you observe this packet? Do you have a possibility for sniffing the wireless traffic? E.g. A RasPi plus the mrf24j40 should do it.
Can anyone give me a hint where to search for the place where netdev2 is
triggered to fill the tx-buffer and send the frame ( I guess an Ack-Frame)?
As said, there is not ACK frame transmission triggered by netdev. In a usual configuration, there is the gnrc_netdev2 thread which calls the gnrc_netdev2_ieee802154 _send function.
This function is implemented by the device driver and usually results in writing the dara to the radio tx buffer as well as triggering the actual transmission.