We have been using the cheap ESP8266 wifi unit for some time for the Spines we have shipped (for the customers accepting experimental stuff).
In particularly it has been the Nodemcu 1.0 or Wemos D1 Mini, but we have run into some issues about the wifi network that we cannot seem to solve ourselves. The bugs we encounter in particularily are problems in dense wifi areas, and we have tried to resolve it by changing wifi output power and also wifi channels etc without luck so far. Maybe it will be resolved with later SDK's and Arduino updates, but for now we will try to look into other hardware as well.
We never encountered any of these problems when using the Arduino Yun.
Features we would like to implement:
Check out our current ESP8266 implementation:
So things are progressing, the brain has been defined and now is almost done with the schematic design and also started designing the PCB, check out the current state below.
So finally got all the connections routed. It was really quite difficult as its the most complex pcb design I have ever made. I had to learn to use another tool in the process as 123d.circuits.com is not really up for the task. I was chosing between KiCad and DesignSpark PCB, and ended up with DesignSpark PCB as I thought it was a little easier to learn.
The board below is using 4 layers, and I used the autorouting feature in the tool extensively, im not sure this is how the professionals are doing it, but Im rather lazy:)
The board has a bunch of connectors for external stuff, as well as a few plug in boards such as, a NodeMCU 1.0, a Teensy 3.2, a NRF24L01 module, and an accelerometer/gyro.
We just placed an order at https://oshpark.com and now wer are waiting to test the first PCB's to see if we made any mistakes.