# Q2686 UART Buffer size **URL:** \ **Category:** Legacy AirPrime modules\ **Created:** [April 26, 2011, 6:15am UTC](https://forum.sierrawireless.com/t/q2686-uart-buffer-size/5031 "2011-04-26T06:15:54Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![awneil](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@awneil](https://forum.sierrawireless.com/u/awneil)\ **Post date:** [April 26, 2011, 6:59am UTC](https://forum.sierrawireless.com/t/q2686-uart-buffer-size/5031/2 "2011-04-26T06:59:21Z")
> [@aezakmi](#): > > In ADL user guide[v6.30] , they mentioned , UART receive buffer can receive maximum 120bytes. Where, exactly, in the ADL USer Guide did you read that? I think you are confusing the UART (hardware) with the Flow Control Manager (FCM) - an ADL service? This has nothing to do with the UART hardware - it is in the nature of how FCM gathers received bytes to be delivered to the Data Handler. It would be very inefficient if FCM were to make a Data Handler call on every single received byte…! > [@](#): > > while receiving, where we need to change the maximum level to 120 from 56. No, you do not need to - and you can’t, anyhow! You must write your code to receive the data in whatever arbitrarily-sized “chunks” FCM decides to deliver it in! > [@](#): > > I gone through the previous posts related to almost same question, like viewtopic.php?f=109&t=4843&p=19774&hilit=fcm#p19774 When referencing a post, you need to post the full URL - it is the forum that abbreviates it when it automatically converts it to a clickable link. (in MS IE, right-click the link, and choose ‘Copy Shortcut’). I take it you mean this: [FCM and WIP - #10 by awneil](https://forum.sierrawireless.com/t/fcm-and-wip/4407/10) > [@](#): > > can not get where to mention the maximum bytes Isn’t it clear in that post: > [@I](#): > > The FCM data handler tells you precisely how many characters it is passing to you - you have to design your handler to accept one or more bytes at a time. Again, You must write your code to receive the data in whatever arbitrarily-sized “chunks” FCM decides to deliver it to you! See also: [Send data fromQ2686 to microncontroller through uart2 - #6 by awneil](https://forum.sierrawireless.com/t/send-data-fromq2686-to-microncontroller-through-uart2/4728/6) > [@](#): > > Your code must cope with the data being delivered in arbitrarily-sized “fragments” And: [FCM Newby - #5 by awneil](https://forum.sierrawireless.com/t/fcm-newby/4115/5) > [@](#): > > It’s possible [likely] that a response will be delivered in more than one Data event; so you will need some sort of state machine to collect response bytes until you get a complete response - but that’s no different to what you’d do on a “normal” microcontroller. --- _[View the full topic](https://forum.sierrawireless.com/t/q2686-uart-buffer-size/5031)._