# HL7802 does not respond to AT command

**URL:** <https://forum.sierrawireless.com/t/hl7802-does-not-respond-to-at-command/27312>\
**Category:** HL78\
**Created:** [June 23, 2022, 1:23pm UTC](https://forum.sierrawireless.com/t/hl7802-does-not-respond-to-at-command/27312 "2022-06-23T13:23:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Ismaiyl](https://avatars.discourse-cdn.com/v4/letter/i/c0e974/32.png) [@Ismaiyl](https://forum.sierrawireless.com/u/Ismaiyl)\
**Post date:** [June 23, 2022, 1:23pm UTC](https://forum.sierrawireless.com/t/hl7802-does-not-respond-to-at-command/27312/1 "2022-06-23T13:23:47Z")

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Hi guys,

I want to use the HL7802 to send data via GSM, VGPIO is equal to 1.8V so the model is on but when I send the AT command via UART1 there is no response.

When I check the voltage in UIM1\_VCC = 0.6V normally it should be 1.8V.

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**Author:** ![jerdung](https://avatars.discourse-cdn.com/v4/letter/j/82dd89/32.png) [@jerdung](https://forum.sierrawireless.com/u/jerdung)\
**Post date:** [June 24, 2022, 11:11am UTC](https://forum.sierrawireless.com/t/hl7802-does-not-respond-to-at-command/27312/2 "2022-06-24T11:11:43Z")

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Hi @Ismaiyl  
Welcome you to our community!  
Could you please share with me some information as below:

1. Are you using Windows or Linux operating system ? If Windows operating system, please share with me screenshot of Device Manager

2. COM port default baud rate is 112500, What baud rate are you using ?

3. Have you installed the driver for the HL7802 module ? If no, please refer to  
[CDM20828\_Setup\_UART\_Driver.zip](https://forum.sierrawireless.com/uploads/short-url/h4m7Yg1QSem8NKIi337T9zQ8zmp.zip) (3.6 MB)

4. What firmware version is your HL7802 running? if it’s not the latest and you already checked the step 2 and step 3, please try again with the latest firmware version. Refer to link: [https://source.sierrawireless.com/resources/airprime/software/hl7800-firmware/hl78xx-firmware-4,-d-,6,-d-,9,-d-,4/#sthash.Qr5QMdjf.dpbs](https://source.sierrawireless.com/resources/airprime/software/hl7800-firmware/hl78xx-firmware-4,-d-,6,-d-,9,-d-,4/#sthash.Qr5QMdjf.dpbs)

Thanks,

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<div class="post-metadata">

**Author:** ![Ismaiyl](https://avatars.discourse-cdn.com/v4/letter/i/c0e974/32.png) [@Ismaiyl](https://forum.sierrawireless.com/u/Ismaiyl)\
**Post date:** [June 24, 2022, 11:48am UTC](https://forum.sierrawireless.com/t/hl7802-does-not-respond-to-at-command/27312/3 "2022-06-24T11:48:53Z")

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Hi @jerdung  
Thank you for repaly.

1. I am using Windows as operating system, I did not communicate with the HL7802 via USB as this is disabled by default, so I used UART1 and sent the command via STM32.

2. I am using a baud rate of 112500

3. Is it necessary to install the driver for the HL7802 although I am using the card with STM32 and HL8702?

Thanks.

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**Author:** ![jerdung](https://avatars.discourse-cdn.com/v4/letter/j/82dd89/32.png) [@jerdung](https://forum.sierrawireless.com/u/jerdung)\
**Post date:** [August 11, 2022, 3:36am UTC](https://forum.sierrawireless.com/t/hl7802-does-not-respond-to-at-command/27312/4 "2022-08-11T03:36:09Z")

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Hi @Ismaiyl ,  
Please refer to how to create communication between HL7802 and STM32 by below link: [Connecting STM32 Nucleo-based application to AirVantage - avc - Sierra Wireless](https://source.sierrawireless.com/airvantage/avc/howto/hardware/samples/nucleo-hl-mqtt/)

Thanks,