RAK811 LoRaP2P sending crashes on specific configurations

[AidenMorton]

I have a RAK811 WisDuo in LoRaP2P mode and i’m trying to send a 72 character payload with the following configuration:
64 Symbol Preamble
12 Spreading Factor
125,000 Bandwidth
4/8 Coding Rate
869,525,000 Frequency

Config command being: at+set_config=lorap2p:869525000:12:0:4:64:20

I’ve found that the RAK will crash and hang, failing to send a packet acknowledgement “[LoRa] P2PTxDone.” when sending a packet larger than 10 characters at 64 preamble.

Note that when I set the preamble to 40, i can send 40 characters.

I think i’ve tracked it down to the base RUI API that’s causing this. The “rui_lorap2p_send” function call at line 327 here (https://github.com/RAKWireless/Products_practice_based_on_RUI/blob/master/based%20on%20RAK811/app_RAK811/at_cmd.c)

It seems to be some sort of overall packet length thing, as when i shorten the preamble, I can send a larger message.

Could someone inform me whether there’s a fundamental reason why this isn’t possible with LoRa or is this just a bug with RAK firmware?

[Nicholas]

Can you tell me your current version number? As well as the error in the operation, more clearly show me, thank you!!

[AidenMorton]

Hi Nicholas,

RAK811 Version:3.0.0.12.H
So the top terminal in the picture is a “sender” RAK, and the bottom terminal is a “receiver” RAK. but both are set to the same config as can be seen in the picture.

Sending 10 characters (the first at+send=lorap2p:c0ffeefeed) works fine and is received fine.
But sending more than 10 characters (on this preamble length) causes a P2PRxError on the receiver and the sender crashes and does not get a P2PTxDone message. After this i cannot send any commands to the RAK811, I have to reset it.

Note that in previous tests, altering preamble to 40 symbols allowed me to send up to 40 characters before exhibiting the same crashing behaviour.

[leopold (wang)]

Hi @AidenMorton
RSSI:-123,Why is the signal so weak?Is it not connected to the antenna, or is it too far away?

[AidenMorton]

Antenna wasn’t connected!
Connected the antenna and tried again, just for completeness and found the same issue

[leopold (wang)]

How many nodes do you use to test send? How long is the delivery time?

[AidenMorton]

I have tried several different RAK811s, this is just between 2 of them. The packet is never fully delivered because the RAK crashes. but it is about 5 seconds before the P2PRxError appears on the receiver node. and the sender node does not recover and has to be reset.

[leopold (wang)]

1.When multiple nodes send data at the same time in p2p mode, they will interfere with each other and are prone to RxError.
2.

@AidenMorton

The packet is never fully delivered because the RAK crashes

The sending time is closely related to the parameters of P2P, especially SF and Symbol Preamble.

We have a new version coming out next month that will send a maximum of 236 characters with the AT directive.Limit condition test:Data lenghth=236, SF=12,Symbol Preamble=65535,send time is about 40 minutes.

[AidenMorton]

@leopold

1.When multiple nodes send data at the same time in p2p mode, they will interfere with each other and are prone to RxError.

I was only testing one transmitter to one receiver. One transmitting at one time.

I understand SF and Symbol preamble, I chose 64 preamble so the preamble would be 2.1 seconds long. but the current version does not allow a 64 symbol preamble with a payload greater than 10 characters.

So this new version has a maximum of 236 characters with AT, what is the current maximum?

[leopold (wang)]

@AidenMorton
The current maximum valid data length is 236 characters with AT.
“at+send=lorap2p:X” the X is valid data,its maximum lenghth is 236 characters now.