Fast forward a year. A long year. A year of almost no hacking - Arduino, Pi, nothing... On a whim, I broke out my Pi and started messing with the GPIO interface and soon had a BMP085 sensor connected to a Python script, writing temp data into a csv file. Pretty cool! Not included to quit while I'm ahead, and finding myself waiting on a couple of clients (and therefore with some 'flexible' time), I decided to break out the NodeMCU. Turns out, someone had gotten the BMP085 working on NodeMCU. After several hours across a couple of days, and running into a steep learning curve, I finally got my BMP085 working on NodeMCU as well!
NodeMCU - This Ain't a Piece of Pi (or Arduino)
OK so you want to jump aboard the IoT craze and get involved. You're familiar with Arduino but you want something lighter, faster, and network enabled. That fancy NodeMCU dev board has been calling you, right?
All in all, it's a nifty idea and it works well (once you get past the learning curve). But if you're coming in from Visual Studio, from Xcode or even from Arduino Studio, be warned: this is not a polished experience. In fact, it's pretty ugly and dirty. Lots of flashing, formatting, serial communications await you before you actually have a working application. It is definitely not for the faint of heart, but if you persist, you'll get there.
Not a Tutorial
This article isn't a tutorial, per say, but a collection of things I picked up over the past few days. Really, there are 3-4 'gotchas' that I'm going to document. There are plenty of tutorials out there, but many of them skip over the 'what the heck do I do now' scenarios. Hopefully I can fill in the gap for you a bit:
- Flashing can be tricky. Use Windows.
- Establish a serial connection as the Node device powers up, so you can see any error messages.
- Debugging is a pain - you need to check for messages as soon as the device boots.
Flashing
I did most of my work on my Raspberry Pi--not really sure why except that it's a throw-away environment where I'm always in screen or minicom, so I wasn't overly concerned about messing things up, and I had all the tools I needed. It might be faster to work elsewhere (I'm running a Pi 3 B+ so it's actually not heinous). There's even a fancy flashing tool (esptool) available for Linux. However... don't do it. I ran into a really weird issue where I saw symptoms like:
- Device showed up online, but worked 'wonky'
- I could program it in Arduino studio with the NodeMCU plug in
- I could not connect to it on Linux over serial comm, unless I tried 115200, but even then things were just weird.
I tried refreshing it with the esptool, which appeared to succeed, but which in the end actually failed.
The answer? Use the Windows flasher tool to flash the build. I spent a good 2 hours one evening digging around trying everything I could think of and finally powered up a Windows machine, flashed it and <poof> everything worked great.
Don't. Seriously, just don't flash it on Linux. Use Windows. It's worth the time you'll save.
Establish Serial Quickly
When the NodeMCU powers up, it very quickly spits some diagnostics to the serial port. It's important that you catch those diagnostics, to be sure you see any messages that might crop up, oh, if your code has a syntax error or such. There is NO INTELLISENSE and NO DEBUGGING on this platform. If you write a mistake, you're not going to catch it any other way besides 1) manual code review or 2) catching the Node as it boots. So be quick on the "screen /dev/ttyUSB0 9600" command, as soon as that device boots.
Debugging
I said it above, but... I created a web page to serve up my inside temp information. I had some syntax errors on the page (not surprising, since I was editing in Leafpad and had some rather convoluted HTML code). I tried three ways from Sunday to get the thing to run. I rebooted it 15 times, but each time I tried to connect, Safari or Android Chrome responded with a connection reset error. I could ping the device (and get responses), but it just wouldn't serve a page.
So then I remembered my point about establishing serial quickly. The next time I powered up, I opened up a serial console ASAP and sure enough - the device spat out some error message about malformed HTML. Fixed it and I was good to go, but I lost a couple hours on this.
Conclusion
I see a lot of great uses for the NodeMCU devices. Remote weather stations no longer need wires. You can put moisture sensors in the far corners of your damp basement. I'm even planning to use one for model rocket telemetry information. It's really a clever device, and the Lua language is rather fun to use. This is going to be a fun device in my arsenal. Keep an eye, by the way, at my other blog securitygeezer.blogspot.comsecuritygeezer.blogspot.com because I have a feeling the NodeMCU device is going to come in handy on penetration tests and such.
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