# Log data from UART0 and UART3

**URL:** <https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411>\
**Category:** HL78\
**Created:** [July 29, 2021, 11:00am UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411 "2021-07-29T11:00:20Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![andrey.gulyants](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@andrey.gulyants](https://forum.sierrawireless.com/u/andrey.gulyants)\
**Post date:** [July 29, 2021, 11:00am UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/1 "2021-07-29T11:00:20Z")

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Hi there,

We would like to collect logs from HL78 in the deployed devices to be able to analyze them in case any connection troubles.

We use UART1 as the main port to communicate with HL78.

The datasheet shows that UART0 (Diagnostic Interface) can be used for this purpose.  
But there aren’t any details related to UART3 (Modem Logs Interface).

The questions are:

1. Is UART3 mandatory to get logs when UART0 is already used?
2. Are the log information getting from UART0 includes the same log data getting from UART3?
3. Is it possible to use 2 wire (RX, TX) connection for UART3?
4. Are there any documents describing the log data structure and content getting from UART0 and UART3?

Thanks.

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**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:** [July 29, 2021, 11:04am UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/2 "2021-07-29T11:04:57Z")

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You need to use uart0 to get log

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<div class="post-metadata">

**Author:** ![andrey.gulyants](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@andrey.gulyants](https://forum.sierrawireless.com/u/andrey.gulyants)\
**Post date:** [July 29, 2021, 1:06pm UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/3 "2021-07-29T13:06:08Z")

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Thank you for your reply.  
Could you please clarify what is data can be obtained from UART3 and would it be useful to analyze it in case of connection issues?

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<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:** [July 29, 2021, 1:29pm UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/4 "2021-07-29T13:29:20Z")

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I don’t even see the physical pin in product technical specification…

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<div class="post-metadata">

**Author:** ![andrey.gulyants](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@andrey.gulyants](https://forum.sierrawireless.com/u/andrey.gulyants)\
**Post date:** [July 29, 2021, 2:15pm UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/5 "2021-07-29T14:15:20Z")

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This is from HL780x product technical specification:

 ![Screenshot 2021-07-29 150912](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/9/95a8a4fe8a07e7008e0f17fa89e5c1929532cdb1.png)

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<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:** [July 29, 2021, 2:32pm UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/6 "2021-07-29T14:32:34Z")

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i did not try this port before…  
Did you see any output there?

BTW, you might need to see if AT+KHWIOCFG can configure these GPIO in your FW.

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<div class="post-metadata">

**Author:** ![andrey.gulyants](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@andrey.gulyants](https://forum.sierrawireless.com/u/andrey.gulyants)\
**Post date:** [July 29, 2021, 7:33pm UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/7 "2021-07-29T19:33:37Z")

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I don’t see any activity at UART3 pins

AT+KHWIOCFG? shows the following response:

+KHWIOCFG: 0,0  
+KHWIOCFG: 1,0  
+KHWIOCFG: 2,0  
+KHWIOCFG: 3,0,6  
+KHWIOCFG: 4,0,8  
+KHWIOCFG: 5,0  
+KHWIOCFG: 6,0

OK

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<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:** [July 29, 2021, 11:09pm UTC](https://forum.sierrawireless.com/t/log-data-from-uart0-and-uart3/24411/8 "2021-07-29T23:09:54Z")

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Did you see any data output there?

Btw, why don’t you use uart0 to take log?