esp8266 micropython uasyncio experimental build

Esp8266 is the super cheap chip which can run Micropython. You can buy it on Amazon for as little as €8 or less, and as little as $5 or less on Bangood/AliExpress.

The ESP8266 (ESP-12E spec) has a 4MB Flash RAM and about 96KB of  RAM. 

One nice thing is you can use an async mode easily  and it works great. So I took this very good complete tutorial on asyncio, and hacked a bit the micropython source code to offer to you a super-breeze async version
First of all I taken the last version of Micropython (1.10) and started to push to its limit to offer at least 44Kb to the interpreter. 51Kb is the theoretical limit, but you must left some space for the interpreter to work correctly.
To increase Micropython available memory, you must download Micropython source code and hack it. It is a bit complex, so a Linux machine is recommended, anyway I managed to to it on a Windows10 with linux subsystem (WSL) which is a bit slow but it is a nice environemnt to work with.
On this forum [1]  I found some specific information, then I forked micropython code base (below you will find my proposed modifications, also a pre-made image is provided).

Overview

First of all edit heap size in main.c
This step needs a bit of caution, because the interpreter needs RAM to work correctly, but you can try to grab a few kilobytes

// From 36Kb....
STATIC char heap[36 * 1024];
// to whoppy 44Kb
STATIC char heap[44 * 1024];

Then we will liste all the C modules pre-compiled, using the help function:

>>> help('modules')
__main__          hashlib           socket            upip
_boot             inisetup          ssl               upip_utarfile
_onewire          io                struct            urandom
_webrepl          json              sys               ure
apa102            lwip              time              uselect
array             machine           uasyncio/__init__ usocket
binascii          math              uasyncio/core     ussl
btree             micropython       ubinascii         ustruct
builtins          neopixel          ucollections      utime
collections       network           ucryptolib        utimeq
dht               ntptime           uctypes           uzlib
ds18x20           onewire           uerrno            webrepl
errno             os                uhashlib          webrepl_setup
esp               port_diag         uheapq            websocket
flashbdev         random            uio               websocket_helper
framebuf          re                ujson             zlib
gc                select            uos

Now the best way is to “scaffold” your micropython for the final target use. For instance I do not plan to use neopixel or frameuffers, because my little esp8266 will act like a server for tuning stuff on and off.

Also webrepl and websocket could be ripped off. At the end of my work, I ended with the following module list

__main__          io                struct            uos
_boot             json              sys               upip
_onewire          lwip              time              upip_utarfile
apa102            machine           uasyncio/__init__ urandom
array             math              uasyncio/core     ure
binascii          micropython       uasyncio/queues   uselect
builtins          network           uasyncio/synchro  usocket
collections       ntptime           ubinascii         ussl
dht               onewire           ucollections      ustruct
ds18x20           os                ucryptolib        utime
errno             port_diag         uctypes           utimeq
esp               random            uerrno            uzlib
flashbdev         re                uhashlib          websocket
gc                select            uheapq            websocket_helper
hashlib           socket            uio               zlib
inisetup          ssl               ujson

I have prepared a forked git hub repository with my hacks [3]: look at the  daitan-hacks branch.

 

Download the ready made image!

  1. “Super Expander” version (Work in progress) 40Kb with basic uasyncio and no webrepl
  2. esp8266-experimental-v1.10.bin.zip Simpler version with asyncio and more RAM

Reference

[1] https://forum.micropython.org/viewtopic.php?t=4813 
[2] Micropython reference
[3] GitHub source