Author Topic: LoRa data doesn't get recieved when over a certain length.  (Read 924 times)

dave_sausages

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LoRa data doesn't get recieved when over a certain length.
« on: September 13, 2016, 08:36:49 PM »
I'm thinking I've found the maximum data length that you can transmit with a LoRa, but I'm not sure, it's always listed in octets and that confuses me.

When I send this "0,0,-6,0,0,0,0,0,0" it is received fine at the other end.

But when my sending unit collects some more data and fills in the zeros and makes this: "0,0,-6,0,0,0,389,0,398" the receiving node stops receiving the data and printing it on the serial interface.

Have I reached the message length limit on my LoRa module?

**edit** I have now found that if I comment out this line that puts it in slow and long distance mode on both modules, it works fine.
Code: [Select]
rf95.setModemConfig(RH_RF95::Bw31_25Cr48Sf512);

But I'm not using the reliable datagram library, so there should be no timeout's happening, and the data is sending once every 5 seconds, and takes 1.2 seconds to send according to rf95.mode(), so why's it not working with large data at slow rates? the units are 1m apart too.

« Last Edit: September 13, 2016, 08:46:00 PM by dave_sausages »

Tostaki

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Re: LoRa data doesn't get recieved when over a certain length.
« Reply #1 on: September 14, 2016, 03:51:27 AM »
According to the LoRa Calculator, you should have a 1381ms Air time.
So far I did not test which more than 15 Bytes payload. I had no issue to get data transfered. The library works, according to the code, with a maximum 251 bytes payload

By using the HeaderXXX() functions I prevented the payload to be transmitted and / or received. Did you used that ones ?

« Last Edit: September 14, 2016, 04:11:11 AM by Tostaki »

dave_sausages

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Re: LoRa data doesn't get recieved when over a certain length.
« Reply #2 on: September 16, 2016, 12:46:32 AM »
According to the LoRa Calculator, you should have a 1381ms Air time.
So far I did not test which more than 15 Bytes payload. I had no issue to get data transfered. The library works, according to the code, with a maximum 251 bytes payload

By using the HeaderXXX() functions I prevented the payload to be transmitted and / or received. Did you used that ones ?
Can you explain what you mean? I don't understand. I am just using this to send the data:
Code: [Select]
 sendLen = strlen(buffer);  //get the length of buffer

  rf95.send((uint8_t*)buffer, sendLen + 1 );

Tostaki

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Re: LoRa data doesn't get recieved when over a certain length.
« Reply #3 on: September 19, 2016, 03:39:33 AM »

Ok if you did not used the header function, that does not come from there. The +1 is a bit weird. According to the lib examples, there is no +1.
By the way, how is the RSSI value when transmitting ?

For the send code, just try

Code: [Select]
rf95.send((uint8_t*)buffer, sendLen);