Pi vs Arduino vs NodeMCU vs ???

It's official - the Internet of Things has a lot of, um... things. So many options! Consider this: my friend and I are working on a weather station. Of course, it can't just be a simple weather station, it eventually needs to be a cluster of stations that can be used to measure differences in micro-climates. More on that later, LOL.

The initial goal is to put a weather station on a roof, without wires. With so many little devices, the question is simple: which is the right device for the job?

• I started in on this the other day when I started messing around with the GPIO pins on the Pi. In about 10 min, I was reading in temp and barometric pressure data and thought "Dang, that's easy!". The Pi is awfully powerful and, now with the Pi 3, wifi-enabled.
• And then there's NodeMCU. Very cool little wifi-enabled device that can take signal on a variety of analog, digital and serial-dedicated pins. And then it can run Lua to actually form that data into "IoT" capable packages, like HTML pages or JSON packets. Finally, it can be a rudimentary http server, so data can be retrieved (conversely it could be written as a client, to push data directly into the cloud). Seemed to me to be the perfect solution.
• My friend Chuck is a strong advocate for using the Pi with an Arduino on a Pi alamode board. The arduino collects the data, the alamode board pushes that data into the Pi, and the Pi processes it.

My take? I see four viable solutions for getting the data off the Sparkfun weather shield and into "a consuming sink" such as the cloud, a data aggregator like a database, or published to the web.

1. Weathershield to Pi via GPIO interface
2. Weathershield to Pi via Arduino
3. Weathershield to NodeMCU
4. Weathershield to Arduino with WiFi chip

Each solution has advantages and disadvantages, and that's what we're doing to explore now.

Weather Shield to Pi via GPIO

This is an elegant solution - it requires the Weather Shield, some connecting wires, and a Raspberry Pi. It's elegant in that there are few moving parts - wire it up, good to go. Right? Wrong. Not all of the Weather Shield components seem to have Python libraries available, which means the coding would need to be done in C. Not impossible, but not necessarily straightforward.

Acquisition cost: 

• Weather Shield: $39.95 + shipping
• Raspberry Pi 3: $35.95 + shipping
• Misc parts: $5
• Total: $80

Development effort:

• Moderate to high

Weather Shield to Pi via Arduino

This is the easiest solution to build, frankly. The weather shield runs great on the Arduino, all sorts of libraries and sample code abound on the Internet. 

Acquisition cost:

• Weather Shield: $39.95 + shipping
• Raspberry Pi 3: $35.95 + shipping
• Raspberry Pi Alameda: $35.00 + shipping
• Misc parts: $5
• Total: $115 + shipping

Weather Shield to NodeMCU

By far the most elegant solution, holy cow... Suspend disbelief briefly and take a walk with me... You have a weather station on the roof, which feeds data into a Sparkfun weather shield. That shield, in turn, feeds data into a NodeMCU chip - tiny, quarter-size chip with wifi on it. The NodeMCU does three things: 1) it pushes the data to a cloud service, every N minutes; 2) it serves the data up via JSON string to anyone on the local network, and 3) it serves up data via formatted HTML on the local network. Awfully cool, and the cost? Nominal.

What's the issue? Simple - the libraries for the components of the weather shield only exist in part, and it's a process of porting them to Lua to make them work. The other problem: NodeMCU only has a single analog pin, whereas the weather board uses three or four.

--> Caveat: the NodeMCU *can* be programmed via Arduino, using Arduino libraries. I need to look into this more; not sure if there's enough memory to do it, though. And the Arduino environment has convoluted support for outputting HTML. I think I just need an afternoon to figure it out though. But still, the bottom line is it's not the right tool for this job.

Acquisition cost:

• Weather Shield: $39.95 + shipping
• NodeMCU: $15.00 + shipping
• Total: $55 + shipping

Weather Shield to Arduino with Wifi Chip

This solution is honestly just a variant on the above solution - the weather shield speaks to an Arduino (great library support) and the Arduino uses a Wifi chip on a shield to publish the data. 

Slightly more expensive than the standalone NodeMCU solution:

• Weather Shield: $39.95 + shipping
• Arduino Uno $24.95 + shipping
• Ada fruit Huzzah wireless shield: $39.95 plus shipping
• Total: $105 + shipping

Summary

The cheapest possible solution, using the Weather Shield with NodeMCU, is not possible because NodeMCU only has a single analog pin and the weather shield needs multiple. That doesn't mean NodeMCU isn't a useful tool - I have a couple of other projects it might be perfect for. It does mean, however, that it's the wrong tool for this job.

From a financial perspective, the lowest cost solution is the Weather Shield plus the Raspberry Pi. It presents some problems - probably not insurmountable, but there'll be some effort to integrate the Weather Shield natively into Pi via Python or C. The time spent may not be worth the money saved over the alternatives (which both make use of an Arduino to read and interpret results).

So a little research is needed, to see how well the Pi can work with the Weather Shield's components. That's how to solve this specific application, but making a global rule overall? Globally I think it's easy to say that the NodeMCU is a low-cost solution but will almost alway have a steep implementation curve, at least until the dev community matures and catches up with Arduino. Overall from a sheer convenience perspective, the best solution is either 1) Arduino with Pi or 2) Arduino with wireless.

Bottom line: my buddy Chuck is right. When I insisted I take some time to look into building this solution with something other than Arduino, he told me I was wasting my time. I *was* right in that it would be more elegant, but he is right from a practical perspective. Everything is just "there" and ready to use, if Arduino plays a role in the solution.

NodeMCU for the Absolute Beginner - Lessons Learned

About a year ago, a buddy of mine who knew I was really into Raspberry Pi and Arduino encouraged me to look into NodeMCU. It's an IoT hardware platform with an onboard Wifi chip as well as a linux-based OS which is programmable in Lua. I messed around with it long enough to see it connect to the web and download a test page from Adafruit, but honestly? I was starting my own business and absolutely swamped.

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.

Lost your Raspberry Pi Password?

I dug out my old Raspberry Pi "WarPi" gear today, as it was high time for a refresh. And of course, then it hit me... I forgot the password. What to do? I have hours into this device building Kismet (fixing a double conversion issue), hooking up the GPS, etc.

Well never fear - my buddy Chuck helped me through it. It's a snap:

1. Pull the SD card
2. Mount it somewhere else (I use a Mac, but you can mount it on Windows or Linux or what have you)
3. Open the "cmdline.txt" file
4. Add "init=/bin/sh" to the end of the FIRST line. 
5. Save "cmdline.txt" again, unmount/eject the SD card and reboot the Pi
6. When you get to the command prompt, type "mount -rw -o remount /"
7. Next, type passwd pi and reset your password
8. Next, type sync
9. Then exec /sbin/init
10. Finally, reboot (you can use sudo halt)

Now log in as usual.