# MangOH Yellow - UART1 / Cypress WiFi

**URL:** <https://mangoh.discourse.group/t/mangoh-yellow-uart1-cypress-wifi/3164>\
**Category:** mangOH Yellow\
**Created:** [December 12, 2019, 4:30pm UTC](https://mangoh.discourse.group/t/mangoh-yellow-uart1-cypress-wifi/3164 "2019-12-12T16:30:05Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![nrcrast](https://avatars.discourse-cdn.com/v4/letter/n/ea666f/32.png) [@nrcrast](https://mangoh.discourse.group/u/nrcrast)\
**Post date:** [December 12, 2019, 4:30pm UTC](https://mangoh.discourse.group/t/mangoh-yellow-uart1-cypress-wifi/3164/1 "2019-12-12T16:30:05Z")

</div>

Hi guys,

So I’m trying to talk to the IOT expander UART1, which seems to be /dev/ttyHS0. However, when I connect to pins 12 and 13 (TX and RX) on the IoT connector, I am unable to get the WiFi to start…

I receive a cryptic message:  
Cypress chip MMC recognition may have been overwritten

And then it fails to start. Looking at the schematic, I don’t see that this UART is related to the WiFi in any way, or am I missing something?

-Nick

---

<div class="post-metadata">

**Author:** ![Habib](https://avatars.discourse-cdn.com/v4/letter/h/71e660/32.png) [@Habib](https://mangoh.discourse.group/u/Habib)\
**Post date:** [December 20, 2019, 2:11am UTC](https://mangoh.discourse.group/t/mangoh-yellow-uart1-cypress-wifi/3164/2 "2019-12-20T02:11:09Z")

</div>

If you are doing RX and TX loop back test, you can connect them through a series resistor (e.g. 100 Ohm) to get rid of the issue. It should not happen if you connect any IOT card though.