# IoT Expansion Re-purpose GPIO

**URL:** https://mangoh.discourse.group/t/iot-expansion-re-purpose-gpio/3065
**Category:** IoT Cards
**Created:** [November 15, 2019, 11:26pm UTC](https://mangoh.discourse.group/t/iot-expansion-re-purpose-gpio/3065 "2019-11-15T23:26:00Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![caioporto](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/caioporto/32/1099_2.png) [@caioporto](https://mangoh.discourse.group/u/caioporto)
#### Post date: [November 15, 2019, 11:26pm UTC](https://mangoh.discourse.group/t/iot-expansion-re-purpose-gpio/3065/1 "2019-11-15T23:26:00Z")

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Hi @dfrey and @asyal,

I’m working with Talon to design and develop a new CAN bus IoT Expansion Card with 2 channels. For that it will require 2 SPI slaves to be in the IoT board. However, we only have 1 CS pin. Is it possible to re-purpose one of the GPIOs to assume the CS functionality? Could you point me to where to look at the source code where the SPI pins are defined and how they are added to the device tree?

Thank you very much,  
Caio Porto

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### Author: ![asyal](https://sea2.discourse-cdn.com/flex016/user_avatar/mangoh.discourse.group/asyal/32/78_2.png) [@asyal](https://mangoh.discourse.group/u/asyal)
#### Post date: [November 16, 2019, 9:28pm UTC](https://mangoh.discourse.group/t/iot-expansion-re-purpose-gpio/3065/2 "2019-11-16T21:28:10Z")

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Hi Caio,

I would recommend using a SPI multiplexer on the IoT card.

regards,  
Ashish