# Why serial1 only recv 127 bytes?

**URL:** <https://forum.amebaiot.com/t/why-serial1-only-recv-127-bytes/1988>\
**Category:** Peripherals\
**Created:** [June 16, 2023, 10:38am UTC](https://forum.amebaiot.com/t/why-serial1-only-recv-127-bytes/1988 "2023-06-16T10:38:19Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![oxygenben](https://avatars.discourse-cdn.com/v4/letter/o/4bbf92/32.png) [@oxygenben](https://forum.amebaiot.com/u/oxygenben)\
**Post date:** [June 16, 2023, 10:38am UTC](https://forum.amebaiot.com/t/why-serial1-only-recv-127-bytes/1988/1 "2023-06-16T10:38:19Z")

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![image](https://us1.discourse-cdn.com/flex016/uploads/ameba/original/2X/8/8e178bbedf57581a24bbcd13fe81c0383e59755a.png)  
 ![image](https://us1.discourse-cdn.com/flex016/uploads/ameba/original/2X/0/0b7ffbcda62d567376367bb451ffe7d6def6f2fb.png)

i send 128 bytes once，but the recv length is 127?

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**Author:** ![dakamaster](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.amebaiot.com/dakamaster/32/3588_2.png) [@dakamaster](https://forum.amebaiot.com/u/dakamaster)\
**Post date:** [June 18, 2023, 8:45am UTC](https://forum.amebaiot.com/t/why-serial1-only-recv-127-bytes/1988/2 "2023-06-18T08:45:13Z")

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Hi @oxygenben ,

Please provide the information below to help us evaluate your issue:

1. SDK version
2. Board name
3. Source code causing your issue
4. How to reproduce this issue

Thank you

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<div class="post-metadata">

**Author:** ![oxygenben](https://avatars.discourse-cdn.com/v4/letter/o/4bbf92/32.png) [@oxygenben](https://forum.amebaiot.com/u/oxygenben)\
**Post date:** [June 18, 2023, 9:36am UTC](https://forum.amebaiot.com/t/why-serial1-only-recv-127-bytes/1988/3 "2023-06-18T09:36:38Z")

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Thank you for response at weekends,i have found the solution。  
the SDK version is 3.1.6 & Board name is amb23。

solution is following。

cores\ambd\RingBuffer.h  
#define SERIAL\_BUFFER\_SIZE 128  
===\>  
#define SERIAL\_BUFFER\_SIZE 512