Can't send more than 256 bytes via the LoRa link.

[giuliocorradini]

An assert on SPI recv_buffer lenght prevents sending any message of size greater than 256 bytes.
A consumer mechanism must be implemented to send the whole packet down the link.

Incriminated line in nuttx/drivers/rf/rfm95.c:344

DEBUGASSERT(buflen <= sizeof(recv_buffer));

a solution could be to remove entirely this assert check, and implement a for-loop that read the incoming buffer in chunks of 256 bytes; this lets us leave unmodified the rest of the code.

[giuliocorradini]

It also seems that for buffer values greater than 51, the transmission doesn't work.

When sending less than 52 bytes the TX_DONE flags is instantly activated, while sending more than 52 bytes doesn't set the TX_FLAG ever.

[giuliocorradini]

https://lora-developers.semtech.com/documentation/tech-papers-and-guides/the-book/packet-size-considerations/