# RC7620-1 AT no response

**URL:** <https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928>\
**Category:** RC76\
**Tags:** faq\
**Created:** [May 3, 2022, 8:21am UTC](https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928 "2022-05-03T08:21:32Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![jerry1](https://avatars.discourse-cdn.com/v4/letter/j/8c91f0/32.png) [@jerry1](https://forum.sierrawireless.com/u/jerry1)\
**Post date:** [May 3, 2022, 8:21am UTC](https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928/1 "2022-05-03T08:21:32Z")

</div>

Hi,  
Use the RC7620-1 module to send AT commands. The first few times the module will respond, but after that, the command will not respond.  
 ![image](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/4/4cee398c324181454aeb90a23f25a8df6ded4f0c.png)  
Please help with this issue or what should I do.

---

<div class="post-metadata">

**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\
**Post date:** [May 3, 2022, 8:40am UTC](https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928/2 "2022-05-03T08:40:06Z")

</div>

is problem only happening after +CMUX?  
have you checked +KSLEEP and see if the module has slept?

Are you seeing problem on UART or USB?

BTW, why do you need to touch AT!MAPUART?

---

<div class="post-metadata">

**Author:** ![jerry1](https://avatars.discourse-cdn.com/v4/letter/j/8c91f0/32.png) [@jerry1](https://forum.sierrawireless.com/u/jerry1)\
**Post date:** [May 3, 2022, 9:04am UTC](https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928/3 "2022-05-03T09:04:01Z")

</div>

Hi @jyijyi

Thank you for your reply.  
Make sure there is no sleep. + KSLEEP: 2  
Seeing problems on UART.  
Set UART 1 to transmit AT command

---

<div class="post-metadata">

**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\
**Post date:** [May 3, 2022, 9:24am UTC](https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928/4 "2022-05-03T09:24:22Z")

</div>

do you see problem with USB?  
do you see problem without using +CMUX?

You don’t need to use AT!MAPUART as the default setting already make the UART accept AT command

---

<div class="post-metadata">

**Author:** ![jerry1](https://avatars.discourse-cdn.com/v4/letter/j/8c91f0/32.png) [@jerry1](https://forum.sierrawireless.com/u/jerry1)\
**Post date:** [May 3, 2022, 9:55am UTC](https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928/5 "2022-05-03T09:55:12Z")

</div>

@jyijyi  
Module to be soldered to the designed PCB.We use UART only.  
There will be problems without +CMUX.

---

<div class="post-metadata">

**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\
**Post date:** [May 3, 2022, 9:59am UTC](https://forum.sierrawireless.com/t/rc7620-1-at-no-response/26928/6 "2022-05-03T09:59:56Z")

</div>

how many modules are having this issue?  
I don’t see problem with development kit, so wonder if this is a hardware issue on your board.