May 8, 2018

Adafruit feather boards

There is a whole family of these in what looks like an identical form factor. They all seem to have a LiPo battery connector. They can have ESP8266 modules, ESP32 processors, ARM processors (x), and even AVR processors (typically a 32u4). Prices seem to range from $20 to $35.

Command Line Arduino

I have said many times that I hate and despise the Arduino GUI. Apparently someone out there heard what I had to say and responded. Maybe not in the way I might have chosen, but we now have a command line arduino: Searches on either "command line" or "headless" arduino yield information.

Feather Huzzah32 ESP32

I have most of my experience with the ESP8266, but moving up to the ESP32 (for $20) sounds appealing. Some of what you get with the ESP32 are: If this gets your interest, for the same price consider the "ESP32 thing" from Sparkfun ($20). This has LiPo support, and FT231 usb to serial chip, and 4M bytes of outboard flash. Note that the Huzzah also offers 4M bytes of flash (in the shielded WROOM module, the "thing" does not use the shielded module). Also Adafruit uses the SIL 2104 USB to serial chip, which allows crazy high baud rates. Adafruit mentions the ESP32 IDF (where IDF is "IoT Development Framework"). This is exactly what I want -- a framework for coding in C, using my favorite editor (vim) and Makefiles. Perfect! No lame and crippled arduino system for me. Note that the Hackaday article recommends using git to clone the IDF so you can easily stay up to date.

Feather ESP8266 Huzzah

I am playing with the Huzzah ESP8266 variant, which is a $17 board. The main things differentiating it from the much cheapter NodeMCU boards I have is the LiPo support circuitry and a much faster USB to serial chip (Adafruit uses a CP2104 USB-Serial chip that supports 921600 baud).

It comes pre-programmed with NodeMCU Lua (which I dislike), talking at 9600 baud. This does mean that you can just use it out of the box as long as you have a USB cable. The other suggested option is to use the Arduino GUI, loading the ESP8266 board package into arduino via the "board manager". Downloading from the Arduino GUI overwrites Lua, which is fine by me. If you want Lua again, you can reflash it. Personally, I like to work in C using the ESP8266 SDK.

Oddly enough it has a Schottky diode in series with the battery, which would seem to provide reverse polarity protection (sacrificing 0.2 volts in the process), yet the documentation says that connecting the battery in reverse destroys the board. The regulator is an AP2112-3.3, which has a 0.25 volt dropout. Between the diode and the regulator you are giving away 0.45 volts. I would ditch the diode and take care with battery polarity myself.

This article points out that the board draws 6.5 mA, which is pretty bad for battery life. The CP2104 is a big culprit. The ESP8266 itself will pull only about 10 microamps in deep sleep. The forum discussion proposes using a TPL5110 to control power to the Huzzah to help fix this.
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