Monday, February 1, 2016

ESP8266 ESP-01 and LUA (NodeMCU)

Sometimes the faiths are just too kind. For example I have learned a few days ago about the ESP8266 chip. It has a complete 802.1b/g/n Wifi stack, a few general purpose I/O pins, loads of RAM, an 80 MHz 32 bit CPU and loads of stuff already in the ROM like RTOS to just name one big one.

As it usually is the case with all new hardware nice is pretty much always accompanied by some ugliness creeping around the corner. 8266 is no exception. By default it comes in 2 flavors: as a module that you talk to using AT commands (just like modems) and as NodeMCU module with LUA interpreter inside.

So let's say you bought the ESP-01 module, because it was the cheepest and you have played around with the AT commands for a while. It is really fun for the first hour or so but then with its unexpected reboots and what not programming something that communicates with it (like an Arduino) and making it resilient to all the quirks becomes just distasteful. Another reason for making the switch might be that doing all the communication directly in the chip (as opposed to waiting for user input via serial interface) is just a lot faster (20+ requests per second vs about 1!!!). Luckily enough you actually can load the LUA firmware to the ESP-01.

From this moment on if you're not a Linux user you need to start looking somewhere else because those instructions won't work for you.

First you need the NodeMCU firmware. You can do that locally but you also can (and I would strongly recommend you do that) use the cloud-based service that has been specifically designed for building it. You just enter your email, select the LUA modules you'd like to have available and presto! In a few minutes you'll be sent a link to the binaries.

Once you have it, it is time to upload the firmware to your ESP-01. To do that you'll need the utility (just the one file!). Hooking up the board isn't all that difficult:

The diagram is a taken from

Important note: The D0 when not in firmware upload mode should be connected to VCC (or otherwise used) and the CH_PD pin should be connected directly to VCC (and not for example through a resistor).

Once you've double-checked and triple-checked all the wires, made sure the voltage supplied is 3.3V and NOT 5V (I have BURNED 2 modules just because of that!) and when your module responds to commands in the terminal it is time to finally burn the LUA firmware:

./ --port /dev/ttyUSB0 write_flash 0x0000 nodemcu-*-float.bin

That will do the trick :) Now you get to learning LUA (I like the video tutorial by Derek Banas) and start hacking. Because LUA and NodeMCU are so popular there is a ton of examples on the Internet to learn from. For uploading I strongly recommend you get yourself a copy of ESPlorer which makes the whole experience a lot more approachable for mere mortals.

Happy hacking!

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