Thanks for your response.
- End Device: (driven by microcontroller); NO CTS flow control.
- Coordinator: (running on Digi development board, connected by USB to PC); I don't know.
- The parameters for sleep in both devices (Coordinator and End device): "NORMAL" (i.e., no sleeping). (all sleep parameters are in default value).
I discovered that, if I set a delay > 3 seconds (in the microcontroller software of the End device), the transmission is received on the Coordinator, without problems. The following transmission doesn't need the 3 sec delay.
I was able to repeat this issue, if I use a Terminal soft, such as Tera Term, etc. In other words, if I drive the Digi module from Tera term I need to do a delay like as the microcontroller program.