# How to time-align Rx1 and Rx2?

**URL:** <https://discourse.myriadrf.org/t/how-to-time-align-rx1-and-rx2/6120>\
**Category:** LimeSDR\
**Created:** [20 May 2020 06:38 UTC](https://discourse.myriadrf.org/t/how-to-time-align-rx1-and-rx2/6120 "2020-05-20T06:38:25Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![alephdivbyzero](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@alephdivbyzero](https://discourse.myriadrf.org/u/alephdivbyzero)\
**Post date:** [20 May 2020 06:38 UTC](https://discourse.myriadrf.org/t/how-to-time-align-rx1-and-rx2/6120/1 "2020-05-20T06:38:25Z")

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Rx1 and Rx2 signals on LimeSDR USB using LMS API do not appear to be in time alignment. The timestamps reported by LMS\_RecvStream differ between the two channels and the captured waveforms are shifted from each other. Is it standard procedure to write code to re-construct a FIFO based on the timestamps to re-align them?

Is there are way to just read the two channels interleaved in a single stream, so that if there are any drops, the channels are still synchronized- similar to audio, where left and right are generally interleaved and not separate streams, or GPU textures, where RGBA are interleaved and not separate bitmaps?

-but even if there was perfect code to keep the FIFO from over/underflowing, what is to prevent the streams being started at slightly different times from creating a race condition where the FIFOs start filling at slightly different times?

The LimeSuite GUI software has a “MIMO Mode” - exactly what is that as compared to reading two streams separately? I don’t see anything about it in the LMS API docs - it seems to treat each Rx like a separate FIFO.

Alternatively using ‘MIMO Mode’ in GRC doesn’t seem to do anything to sync the two channels up.

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**Author:** ![Zack](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/zack/32/89_2.png) [@Zack](https://discourse.myriadrf.org/u/Zack)\
**Post date:** [20 May 2020 11:45 UTC](https://discourse.myriadrf.org/t/how-to-time-align-rx1-and-rx2/6120/2 "2020-05-20T11:45:56Z")

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Hi @alephdivbyzero,

Check this document for more information:

> **[LimeSDR-USB\_channel\_alignment\_v01r00.pdf](https://github.com/myriadrf/LMS7002M-docs/blob/master/LimeSDR-USB_channel_alignment_v01r00.pdf)**

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**Author:** ![alephdivbyzero](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@alephdivbyzero](https://discourse.myriadrf.org/u/alephdivbyzero)\
**Post date:** [20 May 2020 15:19 UTC](https://discourse.myriadrf.org/t/how-to-time-align-rx1-and-rx2/6120/3 "2020-05-20T15:19:49Z")

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Great thanks