How to use the static length field when receiving

Question

Hi! 
 My idea of sending a packet would be: 
 -regulary send a packet with fixed length (stated in static length field) to a base: i.e send the temperature =>4byte
-if something went wrong while transmitt (and this becomes recognized) in the next attempt the new temp value (4byte) + the last one (4byte): (=> 8byte) get sent (now plus 1byte payload length information) 
 So i thought i set the static length in transmitter and receiver to 4byte, in case of a neccesary retransmitt the transmitter sends now 8byte data + 1byte addtional payload length information which the receiver takes care about. 
 Is this the way you would use this static length field or do i misunderstand something (i still cant see the benefit using/having the static length field)? 
 The reason i am asking:
According the Reference manual i thought its like having static length = 0 and if mor bytes need to be sent the transmitter does so by adding static length.... problem with this would be though that the receiver configuration would not fit the transmiter any more. 
 RGDS Dominik

Ole Morten · Accepted Answer

The static length field can be used if all packets you want to transmit are the same length. If so, you can omit sending a length field on air, saving a few bits there. If you want to dynamically change the payload length, as you say, you can not use a static length, and instead you must include the length of each packet in the on-air representation (you could in theory omit the length field here as well, and just always send the max length, but that would be very inefficient). 
 However, in general we normally recommend users to instead build on the Gazell library for proprietary use cases, as that is normally a more flexible and worked-through solution. By doing that, you avoid having to manipulate the radio peripheral directly.