SARA-R4/N4 series - AT Commands Manual
UBX-17003787 - R09
C Appendix: UDP Direct Link workflow
Page 297 of 307
C Appendix: UDP Direct Link workflow
C.1 Data from the IP network to the external port
When a UDP data packet is received from the network, its payload is forwarded through the external port as
soon as possible (according to the HW flow control, if any).
Data from IP network
Forward it to external port
(according with HW flow control, if any)
Figure 10: Workflow of data from the IP network to the external port
C.2 Data from the external port to the IP network
When some data comes from the external port, there are 2 parameters involved:
1.
The UDP DL packet size (factory-programmed: 1024 bytes; valid range 100-1472)
2.
The UDP DL sending timer delay (factory-programmed: 1000 ms; valid range 100-120000)
Both parameters are specific for each socket and could be modified by the user. These values are not saved
into the NVM and if not specified, the factory-programmed values are used.
There are 3 different cases that may occur while receiving data from the external port in UDP DL mode:
1.
The received data from the external port is equal to the UDP DL packet size: the received data is
immediately sent to the network
2.
The received data from the external port is more than the UDP DL packet size: the amount of data till
UDP DL packet size is immediately sent to the network, the remaining data is saved into an intermediate
buffer.
3.
The received data from the external port is less than UDP DL packet size: the received data is saved into
an intermediate buffer and sent to the network when the UDP DL sending timer expires. The timer is
reset (it restarts the countdown) every time new data is received from the external port, this means that
the data will be sent to the network after N ms (default 1000 ms) since the last received byte.
The data sent from the serial port is not echoed to the sender.
The configuration of UDP DL packet size and UDP DL sending timer are NOT saved in NVM.
The following diagram shows how the events of external data input and sending timer expire are handled.
