[riot-devel] Netdev2 - Events/Flags wich cause netdev2 to transmit

Peter Kietzmann peter.kietzmann at haw-hamburg.de
Thu Sep 1 09:06:27 CEST 2016

Hi Neo,

Am 01.09.2016 um 01:28 schrieb Neo:
> Hello RIOT radio chip driver developers,
> 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 


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.

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.


In there, the 802.15.4 header is prepared and the net device (netdev2) 
_send function is called


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 


So far, for the moment.

> This are the first bytes inside my transmit buffer which were forced to
> be send:
> transmitbuf[0]= 0x1f
> transmitbuf[1]= 0x41
> transmitbuf[2]= 0x98
> transmitbuf[3]= 0x0
> transmitbuf[4]= 0x23
> transmitbuf[5]= 0x0
> transmitbuf[6]= 0xff
> transmitbuf[7]= 0xff
> transmitbuf[8]= 0x2
> transmitbuf[9]= 0x30
> transmitbuf[a]= 0x7b
> transmitbuf[b]= 0x3b
> transmitbuf[c]= 0x3a
> transmitbuf[d]= 0x2
> transmitbuf[e]= 0x85
> transmitbuf[f]= 0x0
> e.g.
> Thanks a lot,
> Regards,
> Neo
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Peter Kietzmann

Hamburg University of Applied Sciences
Dept. Informatik, Internet Technologies Group
Berliner Tor 7, 20099 Hamburg, Germany
Fon: +49-40-42875-8426
Web: http://www.haw-hamburg.de/inet

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