CC1352P7: what is the largest payload I can send in Wi-Sun and/or CoAp node example

Omid Kandelusy

Part Number: CC1352P7
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi there,

I am trying to see what is the maximum payload size that I can send from a router node to the border router node.
I am also trying to understand if there is any message fragmentation and re-assembly options too and if so how if works in practice.

As of now, I have manipulated the ns_coap_node example to send custom messages using the button press callback:

static void btn_interrupt_handler(uint8_t index) {
    // if (index == CONFIG_GPIO_BTN1) {
    //     if (bcast_send == true) {
    //         bcast_send = false;
    //     } else {
    //         bcast_send = true;
    //     }
    // } else if (index == CONFIG_GPIO_BTN2) {
    //     if (unicast_send == true) {
    //         unicast_send = false;
    //     } else {
    //         unicast_send = true;
    //     }
    // }


    tr_debug("calling: service_request_send");

    coap_service_request_send(service_id, 0, root_unicast_addr, COAP_PORT,
                              COAP_MSG_TYPE_NON_CONFIRMABLE,
                              COAP_MSG_CODE_REQUEST_GET, COAP_DATA_MESSAGE_URI,
                              COAP_CT_TEXT_PLAIN, &data_to_send,
                              sizeof(data_to_send), 0);
}

However, the max payload that I cans send is less than 1490 bytes, actually I was able to send a payload of 1450 bytes, so the actual max size should be something in between the two.

I have realized there is a sysconfig option in the link layer for the max payload size which is set to "2047" bytes by default (which seems to be the max possible)

I am wondering why I cannot send payloads as large as 1500 bytes and that is there a way to increase this limit?
Also, is there any message fragmentation and assembly option?

Thanks.

4 months ago

0 Arthur R☑️ 4 months ago

TI__Mastermind 25315 points

Hi Omid,

At MAC level, we have a 2kB limit.

Fragmentation is handled at the 6LowPAN level.

Regards,

Arthur

0 Omid Kandelusy 4 months ago in reply to Arthur R☑️

Prodigy 170 points

Thanks for your response,
so, is there any stack size or something that prevents the application to run properly? If so, from where I can increase it?
when I increase the payload size to 1500-ish bytes, the app does not receive/send(?) anything.

It would be great if you could tell me what is the blocker for sending segmented messages.
It is critical in our application to convey a large data chunk like 2000 bytes or 3000 bytes, etc.

0 Arthur R☑️ 4 months ago in reply to Omid Kandelusy

TI__Mastermind 25315 points

Hi Omid,

Is the app crashing, or are the packets merely discarded? For instance, once you try sending a 2 kB packet, and it fails, can you still send < 1500 packets afterwards?

Regards,

Arthur

0 Omid Kandelusy 4 months ago in reply to Arthur R☑️

Prodigy 170 points

Before answering you question, there are four things to consider.

1) I am using a static dummy data defined in the global scope as uint8_t data_to_send[1500] = {0}; which means I do not have the luxury of sending variable-length packet as of know. (I can update the basic test app to do that)

2) I tracked the error code, the coap_service_request_send() function returns 0.

3) I increased the WISUNTHREADSTACKSIZE to 8000 and still no change.

4) I am using logic analyzer to track packets being sent and received from the RFcore signals routed to the GPIOs.

The application does not seem to crash as it logs out the log statement "tr_debug("calling: service_request_send");" every time I push the button, so
my guess is that somewhere some logic routine get's truncated by some checkers. Also, I can see the Rf core signals being regularly toggling the GPIO pins excluding the one that corresponds to the large packet transmission.

Thanks.

0 Arthur R☑️ 4 months ago in reply to Omid Kandelusy

TI__Mastermind 25315 points

Hi Omid,

If you set data_to_send to 2048 instead, does the issue persists? The reason is that I think there might be a memory alignement issue.

Regards,

Arthur

0 Omid Kandelusy 4 months ago in reply to Arthur R☑️

Prodigy 170 points

I tried 2048, this one also did not work; yes, the issue still persists.

0 Omid Kandelusy 3 months ago in reply to Arthur R☑️

Prodigy 170 points

Hi there, I would be thankful if you guys could get back to me as soon as you can.
Thanks.

0 Arthur R☑️ 3 months ago in reply to Omid Kandelusy

TI__Mastermind 25315 points

Hi Omid,

I meant to come back asap, while I was trying to reproduce the issue, but here I am.

Can you also increase the buffer-size in the ncp, as well as the baudrate?

Something I should have asked before as well, what PHY are you using? It will of course be easier to send bigger packets, the higher the bitrate goes.

Regards,

Arthur

0 Omid Kandelusy 3 months ago in reply to Arthur R☑️

Prodigy 170 points

Thanks for the reply,

There are two things:

1) I do not see the packet transmission on the router node side, I can verify that by looking at the RF core signals, the router node does not send the packet. Does the router node application which is in fully embedded mode, have dependency on the UART as well?

2) the phy setting I tested was 50Kbps.

0 Arthur R☑️ 3 months ago in reply to Omid Kandelusy

TI__Mastermind 25315 points

Hi Omid,

Thanks for the heads up, the NCP should indeed not have anything do to with it if the packet is not even being sent..

Regards,

Arthur

0 Omid Kandelusy 3 months ago in reply to Arthur R☑️

Prodigy 170 points

Yes, I am wondering what is going wrong with the sending part, I am sure it does not send any packet as I do not see the rfcore gpio toggle on the logic analyzer; however, if I lower the payload size to say 1000 bytes, it sends it and I can see the toggles on the logic analyzer.

0 Omid Kandelusy 3 months ago in reply to Arthur R☑️

Prodigy 170 points

Hi there, I was wondering if there is any update on this issue? thanks.

0 Omid Kandelusy 3 months ago in reply to Arthur R☑️

Prodigy 170 points

HI there, this is just a reminder that I am still waiting for your response.

0 Arthur R☑️ 3 months ago in reply to Omid Kandelusy

TI__Mastermind 25315 points

Hi Omid,

I did not forget, but I still have to observe the problem, and instrument it. In the meantime, I will take any more data/thoughts that you can provide. I still do not believe that it is a good idea to send such a large packet at 50 kbits, as the risk of a bit error occuring is quite high.

Regards,

Arthur

0 Omid Kandelusy 3 months ago in reply to Arthur R☑️

Prodigy 170 points

Here is the results for 300Kbps which is highest data rates for Wi-SUN at two payload size of 1KB and 1.5KB.

RFcore signals of the router node and border router when sending 1KB (routed to GPIOs)

RFcore signals of the router node and border router when sending 1.5 KB (routed to GPIOs)

As can be seen, the router node does not send the message; here is also the router node serial logs:

As you can see, the program is not crashed as I can call the send functions couple of times in row, but it does not send anything which can
be confirmed by just looking at the rfcore signals.

The reason I am interested to send large packet is to see how the segmentation/re-assembly works in TI wisun stack.