RAK3172 AT+PSEND command problem

LPWAN Modules / EVBs
1

Hi everyone.
My device uses the RAk3172 module to send data to the Gateway, both devices are configured to work in P2P mode. Device configurations are as follows:

“AT+NWM=0\r\n”
“AT+SYNCWORD=3444\r\n”
“AT+P2P=903900000:10:125:0:8:\r\n”
“AT+PRECV=0\r\n”
delay_ms(20);
“AT+PSEND=…”

The response to these commands by the RAk 3172 is always OK, as can be seen in the following image:

image

When the information sent in the “AT+PSEN=” command is short or test like “1122334455” the packet is received in the GW. The problem is generated when larger packets such as “3C313732363E6E6F5F646174612A6F6E5F322E3076322E30302D323330353135” or “3C39393E76675941414770367832426B4152646A4168674C4130633342414E694252645A48457741” are sent. Apparently, as the size grows, the package is no longer sent.
What could be happening? Why can’t I see long packets? Isn’t the limit really 500 characters?

image

I have also tried the following configuration without any change in behavior:

“AT+NWM=0\r\n”
“AT+SYNCWORD=3444\r\n”
“AT+RFFREQUENCY=903900000\r\n”
“AT+TXOUTPUTPOWER=22\r\n”
“AT+BANDWIDTH=0\r\n”
“AT+SPREADINGFACTOR=10\r\n”
“AT+CODINGRATE=0\r\n”
“AT+PREAMBLELENGTH=8\r\n”
“AT+PRECV=0\r\n”
delay_ms(20);
“AT+PSEND=…”

image

Attached response to the version command:

image

Thanks for your time.

Regards Daniel L.

2

Welcome to the forum @ldloaizae

I tried to send your payload over P2P from a RAK3172 to a RAK4631 and it works just fine in both directions. RAK3172 to RAK4631:

image
image1718×204 12.9 KB

Sending the other way around:.

image
image1747×339 35.3 KB

What is your “gateway” build with? Is it a RAK3172 as well?

3

Hi @beegee, thanks you for the answer.

My gateway is LG02 from Dragino, based on SX1276/SX1278 LoRa modules, the gateway is not based on RAK3172.

I have some questions:

Is there any reason why the RAK3172 will not send the packet?
Why in the response of the AT+PSEND command is only an OK, where is the rest of the command response? +EVT:TXP2P DONE
What should be the time it takes for the RAK3172 to send a command of that length?

Regards

4

The +EVT:TXP2P DONE response for packet transmits was added in the latest firmware version V4.0.5 which is online now.

There is no reason why the RAK3172 would not send the packet without throwing an error.

Do you have an SDR so you can check whether the packet is really sent?

For the air time of a packet, you can use the SX1261 Calculator Tool from Semtech (sorry, I don’t have the downlink URL, you can find it on Semtech’s website)

With your CR, BW, SF, Preamble length and a payload size of 40 bytes the air time would be ~534ms.

image
image987×538 23.2 KB

Are you in USA? If yes, I would change the frequency from 903900000 to something that is not used by the LoRaWAN packets, like 904000000. On your current frequency, you might have collisions with LoRaWAN packets from other devices. My proposed frequency is unused by LoRaWAN.