Early test code for a mecrisp forth connected to ESP-Link
Dont't expect those examples to do anyting of value.
But maybe they will blow your house or shoot your mother in law - who knows?


Goal in the end:
simple double setpoint control
https://en.wikipedia.org/wiki/Double-setpoint_control
https://de.wikipedia.org/wiki/Dreipunktregler

Which supposed to control the pressure in my heating system
(as some next-to-hello-word example for more complicated IoT tasks)
- read pressure analog in
- agitate relief valve if pressure is too high
- agitate fill pump if pressure is too low
- send notice on any action by MQTT (mosquitto) to home automation (FHEM - planned)
- query pressure and status by MQTT / home automation
- set switch levels and maybe other constants by MQTT


My setup
- Blue pill STM32F103-whatever Controller (cheap China clone)
- Mecrisp-Stellaris RA 2.4.8 for STM32F103 by Matthias Koch
- Wemos D1 mini ESP8266 ESP-12 based china clone
- esp-link v2.2.3 - 2016-06-21 21:58:48 - 1bcdc62
- wlan and (not really simple) home network, of course
- jeelabs embello folie v1 terminal program

Basic steps:

- flash ESP-Link to ESP  (esptool.py)
- folie -p /dev/ttyUSB0 ... watch WiFI setup, connect to AP, set your SSID and switch to station mode
- flash mecrisp to the bluepill
- optional: play with FORTH over a serial line first
- connect bluepill to ESP (same breadboard), with a cheap 5-V-mobile charger for power
- attach a chinese-2-channel-relais-card and apotentiometer to simulate pressure input
- implement a double-setpoint control which is a quite straightforward FORTH-exercise
- digital-I/O, ADC, tasks.....
- try to get MQTT running

this is where I'm currently stuck:
jeelabs/esp-link#430
SLIP MQTT protocol definition for FORTH client implementation

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cutting edge per Tue Jan 29 22:19:11 CET 2019
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some useful links I remeber to have looked up more than once:

Our "wireless USB-cable:"
https://github.com/jeelabs/esp-link/tree/fe4f565fe83f05e402cc8d8ca3ceefbc39692a1f/serial
https://github.com/jeelabs/esp-link/blob/fe4f565fe83f05e402cc8d8ca3ceefbc39692a1f/serial/crc16.c

the workhorse hardware:
http://wiki.stm32duino.com/index.php?title=Blue_Pill
http://wiki.stm32duino.com/images/c/c1/Vcc-gnd.com-STM32F103C8-schematic.pdf
https://embello.jeelabs.org/hardware/bluepill.html

wiring 
https://github.com/jeelabs/esp-link/blob/master/FLASHING.md#hardware-configuration-for-normal-operation
Hardware detail: diode in reset line:
https://jeelabs.org/article/1619a/

really helpful FORTH-I/O libraries, tutorials, .... 
https://embello.jeelabs.org/flib/
https://github.com/jeelabs/embello/tree/master/explore/1608-forth
https://github.com/jeelabs/embello/tree/master/explore/1608-forth/rnw

you will learn to hate telnet, minicom, .... and use:
https://github.com/jeelabs/embello/tree/master/tools/folie

The FORTH to flash onto the BluePill:
http://mecrisp.sourceforge.net/
http://mecrisp.sourceforge.net/glossary.htm

"Mecrisp-Stellaris Unofficial UserDoc 1.0 documentation"
http://hightechdoc.net/mecrisp-stellaris/_build/html/glossary.html
http://hightechdoc.net/mecrisp-stellaris/_build/html/words.html

Some other FORTH reference I consider helpful
https://www.complang.tuwien.ac.at/forth/gforth/Docs-html/index.html#Top
https://www.complang.tuwien.ac.at/forth/gforth/Docs-html/Word-Index.html#Word-Index
http://lars.nocrew.org/forth2012/core.html

A running example for ESP-Link with forth where I picked up much of MQTT low level info:
https://hackaday.com/2017/02/13/hacking-on-the-weirdest-esp-module/
https://github.com/hexagon5un/hackaday_esp-14_power_meter/blob/master/forth_system/mqtt.fs
https://github.com/hexagon5un/hackaday_esp-14_power_meter/blob/master/forth_system/crc.fs
https://github.com/hexagon5un/hackaday_esp-14_power_meter/blob/master/forth_system/messages.fs

RTFS if you can't RTFM due to nonexitence
This is a C-client that is delivered to implement MQTT over ESP-Lib
So I have to implement a subset of its functionality
https://github.com/jeelabs/el-client/tree/master/ELClient/examples/mqtt
https://github.com/jeelabs/el-client/blob/master/ELClient/ELClient.h
https://github.com/jeelabs/el-client/blob/master/ELClient/ELClient.cpp
https://github.com/jeelabs/el-client/blob/master/ELClient/ELClientMqtt.h
https://github.com/jeelabs/el-client/blob/master/ELClient/ELClientMqtt.cpp
https://github.com/jeelabs/el-client/blob/master/ELClient/ELClientCmd.cpp


https://en.wikipedia.org/wiki/Serial_Line_Internet_Protocol

http://mqtt.org/2014/11/mqtt-v3-1-1-now-an-oasis-standard