WiFi + SD + incoming SPI; MCU suggestions?

Projects
1

Hi all, just touching base to see if anyone had suggestions regarding a platform choice.

I wish to develop a small IoT-like package which

  1. acquires data via SPI (24bit depth samples at minimum 1ksps plus protocol overhead)
  2. records these to an SD card
  3. transmits these as JSON objects in small batches over wifi (802.11b/g/±n, WPA2) using https and a SSL certificate
  4. can do so for several hours on a lithium coin cell battery

Several additional desires (far more negotiable);

  • usb
  • small (implemented) footprint
  • evaluation / prototype board available
  • similar architecture to Arduino environment (ie program in C, easy boatloader, support and example implementation available)
  • maybe AVR over other MCU cores?

My first thought was of course Arduino, but unfortunately;

  • SD support is largely at the cost of SPI
  • ram is likely to limit the size of wifi batches (and no native 24bit handling, I believe)
  • second module required to run wifi stack
    So at best possibly doable, but not very feasible

Next I thought of the mass produced esp8266 modules, but again see limitations

  • wifi stack yielding interrupting data acquisition
  • ram may limit wifi packet size
  • Unsure of SPI support
  • no real https implementation

Which left me with mainstream SoCs and modules. One newish one seamed appropriate, the ATMEL SAMW25 and is available as an evaluation board. It would seem that the flash size is overkill, and it only has one free SPI, but it may fit - but the Eval boards don’t seem to be in stock anywhere.
Any thoughts or suggestions?

2

NodeMCU?

3

The esp8266 based nodemcu is quite promising.
While the wifi stack does need servicing, like you say, it is running at 80mhz dramatically faster than an arduino and a lot mor program storage and ram. So there may be the resources to run the spi aquasition, sd card and wifi.
Esp8266.com is the website with forum and resources to read up on it.

Also you have the option of the arduino ide and libraries to use with it.
Ive been using this and it works very well
Or the expressif sdk for best performance. This is on my to do list, havnt had a chance to play yet.