# Hello, why I need re-transmit lot of time in API=1 mode from End device to Coordinator? **URL:** \ **Category:** XBee & XBee Gateway\ **Tags:** xbee-api-mode\ **Created:** [May 7, 2014, 8:15am UTC](https://forums.digi.com/t/hello-why-i-need-re-transmit-lot-of-time-in-api-1-mode-from-end-device-to-coordinator/12914 "2014-05-07T08:15:30Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![vasama](https://avatars.discourse-cdn.com/v4/letter/v/ce7236/32.png) [@vasama](https://forums.digi.com/u/vasama)\ **Post date:** [May 7, 2014, 8:15am UTC](https://forums.digi.com/t/hello-why-i-need-re-transmit-lot-of-time-in-api-1-mode-from-end-device-to-coordinator/12914/1 "2014-05-07T08:15:30Z")
I’m testing two XBee Pro S3B 900HP, configured one of them as Coordinator and another one as End device. The end device is driven by a microcontroller; the Coordinator is connected to a PC by XCTU soft. The both modules are configured API=1. All is OK, except I need to send the API frame from the End device a lot of times (I did a loop in the microcontroller program) before the Coordinator could receive the packet. The delay is around 10 or more seconds. After the first transmission is received, there isn’t a delay for the next. Can you tell me what parameter, etc. I forgot in the configuration.? Thanks in advance. ---
**Author:** ![mvut](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.digi.com/mvut/32/31_2.png) [@mvut](https://forums.digi.com/u/mvut)\ **Post date:** [May 7, 2014, 10:27am UTC](https://forums.digi.com/t/hello-why-i-need-re-transmit-lot-of-time-in-api-1-mode-from-end-device-to-coordinator/12914/2 "2014-05-07T10:27:35Z")
Are you using CTS flow control? Have you verified the path using a Node Discover? Is the end device sleeping? If so, what sleep settings are you using?