# Which pins on the STM microcontroller are connected to the RS485 interface on the dev board?

**URL:** <https://bristlemouth.discourse.group/t/which-pins-on-the-stm-microcontroller-are-connected-to-the-rs485-interface-on-the-dev-board/481>\
**Category:** Application Dev\
**Created:** [February 27, 2025, 3:19pm UTC](https://bristlemouth.discourse.group/t/which-pins-on-the-stm-microcontroller-are-connected-to-the-rs485-interface-on-the-dev-board/481 "2025-02-27T15:19:47Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jaszylu](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@jaszylu](https://bristlemouth.discourse.group/u/jaszylu)\
**Post date:** [February 27, 2025, 3:19pm UTC](https://bristlemouth.discourse.group/t/which-pins-on-the-stm-microcontroller-are-connected-to-the-rs485-interface-on-the-dev-board/481/1 "2025-02-27T15:19:47Z")

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I’m setting up a Seeed RS485 pressure sensor on the dev board and monitoring the output through PuTTY with my laptop connected via the USB-C port on the Mote. However, PuTTY is reporting a serial communication error for reasons currently unknown. I’d like to verify what signal is reaching the STM microcontroller when the error occurs.

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**Author:** ![matt001k](https://yyz1.discourse-cdn.com/flex029/user_avatar/bristlemouth.discourse.group/matt001k/32/497_2.png) [@matt001k](https://bristlemouth.discourse.group/u/matt001k)\
**Post date:** [March 6, 2025, 6:24pm UTC](https://bristlemouth.discourse.group/t/which-pins-on-the-stm-microcontroller-are-connected-to-the-rs485-interface-on-the-dev-board/481/3 "2025-03-06T18:24:17Z")

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@jaszylu, you can find the schematics for the mote and bristlefin (orange board) [here](https://bristlemouth.notion.site/Technical-Documentation-053f9b96f3f143d1a7e12ebb43814ae9).

The following screen capture shows the pins on the MCU:

![image](https://canada1.discourse-cdn.com/flex029/uploads/bristlemouth/optimized/1X/611eb3eb5d7817abbdad77464876c081b3c877cb_2_689x58.png)  
PA2(pin 12) and PA3(pin 13) are the TX/RC lines

I would recommend reading [this guide](https://bristlemouth.notion.site/Bristlemouth-Dev-Kit-Guide-Integrating-an-RS485-Serial-Sensor-10e7e7b1d46e804fad00e5edacdc2975). Specifically the section, `Physically integrate the sensor` which explains some of the jumpers that must be set for RS485 integration.:

 ![image](https://canada1.discourse-cdn.com/flex029/uploads/bristlemouth/original/1X/6b157a878c4bd5072a4ed6b1647e7a3543dbecc0.jpeg)

Let me know how else I can help!