Raspberry Pi Console Adapter

This project is a little less about a cool device and more about thinking through spare hardware.

I ordered a few little NodeMCU breakout boards from AliExpress.   They're very useful little boards and generally replacing Arduinos in my toolbox.   They are easy to code for and I think fairly simple to use.

Then I found the Raspberry Pi Zero Wi-Fi project on Hackaday and built one myself.   But, to get the ESP8266, I didn't buy a new one, I heated up the NodeMCU board and removed the 8266.

That left me with something with very little usability because it has no controller.   But, I didn't throw it away since it might be useful someday.    Little did I know...

As I was configuring the Wi-Fi on the Zero it became apparent that a console cable for the Raspberry Pi would be helpful.    I looked at Adafruit and Amazon and could order one for about $10.    Then I remembered that the NodeMCU has to have a Serial breakout on it of some kind.   Sure enough, it's has a CP2102 onboard.

I know from using the ESP8266 that it's a 3.3v chip and prefers all the signals to be 3.3v.    I suspected then that the CP2102 on the NodeMCU board would also likely be 3.3v.    Looking at the bottom right, there's RX and TX as well as GND.  

Normally, you'd wire up RX to TX and TX to RX.   However, in this case I suspected that the pin labels would be representative of what the ESP8266 would present which should be opposite what the CP2102 presents, because it's wired to talk to the ESP8266.. 

I hooked it up to the Oscilloscope just to be sure and found that indeed I had 3.3v signals coming out of the CP2102 and that RX was really CP2102 TX and TX was really CP2102 RX.   

That means that I hook up this board to the Raspberry Pi GPIO like so:

Node    Raspberry

GND --  GND

TX   --   TX

RX   --   RX

(It has 3.3v output and you could probably power the Zero from it.   Remember you shouldn't dual power the Raspberry.   I chose to not put a 4th cable on for power so I'd be forced to power the Zero from somewhere else.) 

Now to wire it up and test...

And away it goes...

One 3.3v Raspberry Pi Console Cable using spare parts.