Where do I must send/receive 802.11 MAC frames to/from?

[oscargarciaabad]

Hi all,

Currently I'm developing an MQX Wifi driver. This device is sending/receiving 802.11 MAC frames to/from SPI bus. My questions are:

     - When I receive a frame from SPI, How do I send it to RTCS?

     - How do I receive frames from RTCS?

I know there is a structure called PCB (Packet Control Block), but I can't find any documentation regarding this topic. May somebody point out some hints on that topic?

Regards,

Oscar.

[oscargarciaabad]

Hi,

When I receive a PCB from an upper layer, which is the FRAGMENT  endianess?

Regards,

Oscar.

[RadekS]

I am not sure whether I understood your question.

“The PCB structure consists of two pointers (FREE and PRIVATE) followed by a variable-length array of PCB_FRAGMENT structures.  The array is terminated by an entry with LENGTH=0 and FRAGMENT=NULL.”

ENET driver allow spreading packet into more fragments, however RTCS do not support it. It always work with situation where 1 packet = 1 fragment.

Over network we always transfer big endians.

PCB block already contains functions for automatically rotation between big and little endians and in fact it depends on MCU core settings (PSP_ENDIAN) if something will be changed or not.

So, If you will work with PCB, it should be handled automatically.

[oscargarciaabad]

Hi RadekS,

If I got you well the FRAGMENT data ( the Ethernet frame ) will be in the same endianness of the processor I’m running on (ARM Cortex-M4 in my case). Isn’t it?

Regards,

Oscar.

De: RadekS

Enviado el: viernes, 20 de marzo de 2015 14:59

Para: Oscar Garcia Abat

Asunto: Re: - Where do I must send/receive 802.11 MAC frames to/from?

<https://community.freescale.com/>

Where do I must send/receive 802.11 MAC frames to/from?

reply from RadekS<https://community.freescale.com/people/RadekS?et=watches.email.thread> in MQX Software Solutions - View the full discussion<https://community.freescale.com/message/496053?et=watches.email.thread#496053>

[RadekS]

In fact, PSP_ENDIAN depends on compiler option.

In default settings, Little-endian format is used for Kinetis M4 core.

The network headers are typically in Big-endian format.

So, there will be applied translation for network headers.

Anyway, mqx.h contains definitions for convert functions (Host to network / network to host) like mqx_htonl or mqx_ntohl…

I hope it helps you.

Have a great day,
RadekS

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[oscargarciaabad]

Hi RadekS,

Thanks a lot for the help!

Regards,

Oscar.

De: RadekS

Enviado el: lunes, 23 de marzo de 2015 15:52

Para: Oscar Garcia Abat

Asunto: Re: - Where do I must send/receive 802.11 MAC frames to/from?

<https://community.freescale.com/>

Where do I must send/receive 802.11 MAC frames to/from?

reply from RadekS<https://community.freescale.com/people/RadekS?et=watches.email.thread> in MQX Software Solutions - View the full discussion<https://community.freescale.com/message/497029?et=watches.email.thread#497029>

[RadekS]

Yes, you are right. There missing documentation for lowest layer of RTCS stack. We plan to release such documentation during this year (for KSDK1.3).

I would like to recommend take one of already available Wifi patches as inspiration. For some of wifi modules MQX patches was created by third party designers.

Qualcomm/Atheros TWR-WIFI-AR4100 for MQX 4.0.2

GainSpan TWR-WIFI-GS1011M1 and TWR-WIFI-GS1500M for MQX 3.7

Redpine Signals TWR-WIFI-RS2101 for MQX 3.7

These patches you can download from Freescale MQX download pages:

https://freescale.flexnetoperations.com/control/frse/product?child_plneID=683961&ver=ARC

As next inspiration could be taken ENET RTCS adapter in KSDK (fsl_enet_rtcs_adapter.c)

I hope it helps you.

Have a great day,
RadekS

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[oscargarciaabad]

Hi RadekS,

A far as I've seen the implementations does the following (simplified):

You need to create a ENET_MAC_IF_STRUCT for the Mac interface. Here the SEND memeber is the function that will receive the PCB from upper protocol layers.

For receiving packets you need to create a PCB pool. When a a new frame is received, a PCB is allocated from this pooll (using QGET). After this a buffer for the frame is reseved and linked to the PCB. Then calling ENET_find_receiver figures aout the receiver ( upper layer protocol, i.e IP) for the frame. Finally the PCB sent to the receiver calling the SERVICE member of the ENET_ECB_STRUCT_PTR returned by ENET_find_receiver with the PCB as argument.

Am I right?

Regards,

Oscar.

[RadekS]

Hi Oscar,

Yes, is sounds correct.

Best Regards

RadekS