I'm using the modules as a cable replacement. I send a 21 byte packet from the usb stick, and should receive a 21byte packet back from the converter module almost immediately. The problem occurring is I'm getting a severe response delay. I cannot change my program to adjust for those timings. On the hand somebody asks, I use a Zigbee unit set from Sena Industrial and it works amazingly well. I was hoping the Digi unit would work as well so I have two sources for these types of modules.