I have bought a few 900 MHz S3B modules for evaluation. I'm using them in transparent UART mode using point-to-point addressing.
I'm trying to send a stream of 5-byte packets every 33 milliseconds.
Unfortunately, it seems that sometimes, these packets get joined and transmitted later.
Sniffing the 900 MHz band with a spectrum analyzer shows no other traffic nearby, so I don't think this is because of detecting the channel as taken.
I also sometimes (a few times a second) want to send between 2 and 16 bytes the other way.
I thought that I would be able to send this status packet back in response to receiving an incoming 5-byte packet, and there would be enuogh time to turn around the channel, send data back, and then turn around the channel again for the next 33ms interval.
However, it seems that sending the data back, directly in response to an incoming packet, takes the air for about 50 milliseconds. Running at 20 kbps air rate, this seems surprisingly high.
I'm using a packetization timeout setting of 1 character, and a packet-size threshold of 5 bytes.
I'm measuring round-trip times using a logic analyzer on the USART TX/RX for both the transmitting and receiving modules.
Is there some configuration change I can make to get more real-time performance out of this system?