Ethernut

Why do I use Ethernut ?

Ethernut is a nice little controller with a lot of IO-pins. I use it to control heating in my house.
In contrast to the old (version 1) C-control 1 ethernut provides an ethernet-port, ten times increased clockrate, 100 times more RAM, serious programming in C, a GPL development environment and an OS with POSIX support, and no programming restrictions compared to the latest ccontrol.
Ethernut consists of HW and SW. Both are for free under GPL, but HW is easiest bought at egnite. The SW consists of a bundle of application examples and an impressive operating system called Nut-OS.

My application

In writing my heating control SW, I profited much of the helpfull ethernut community. As a give back you find here my source code which you may use as programming example, especially for your own HW control application in your house.

Download: this tarfile contains my enhanced eboot and the application code "Solaranlage", all based on NutOS 3.9.5.

NEW: I totally reworked the code, made it cleaner. I'd not time yet to post it here ...

Features:
  • eboot: the original eboot unconditionally downloads the image on every reset. This wasts write cycles. My eboot first looks for an update indication on the DHCP-server before starting any downloads. for details see the commentary in eboot.c.
  • app/1wire: I introduced two changes into this device driver: first I moved the cpp-definitions for port-accesses from 1wire.c to my application header "Solaranlage.h" in order to rise the level of abstraction. Then I changed some few timings and port accesses in the bit functions; in my view these changes fits better to dallas datasheets. (my HW works: 9 DS1820 on 20m wiring).
  • Solaranlage: this application consists of an header and cfile. It was designed to control my solarthermal facility
  • Solaranlage.h: bit-port access is abstracted by locating the HW-mapping information into a structure, and by using a cpp-function for changing IO-bit-values, eg. ioporset(valve,s,s) sets a "valve" bit to 1. This functions does the job to look for the bit-number and port-id associated to valve. More exaples in Solaranlage.c. The structures support Dallas sensors, analog inputs and output-bits called "Relais".
  • Solaranlage.c:For detailed explanations glimpse into the sourcecode. Some highlights:
  • instead of constraining my input analog ports to 4 (the upper nibble is blocked by JTAG) I preselect 8 inputs by means on the chip LTC1390. Selection is done with "ADSel()".
  • all strings are located in flash in order to relieve RAM. Done with "PSTR()"
  • Dallas devices are read with full precision and crc-check.
  • everybody not requiring sub-kelvin precision for temperature measurement may use a simple NTC instead of Dallas devices. Advantage is a broader temp range and saving money. NTCADC() and NTC2T() read the NTCs and return the absolute temp.
  • I store my sensor data each hour into the eeprom of Ethernut. EepromNew() initializes this job, the Thread Eeprom stores the data and EepromDump() retrieves it into the open stream (V24 or ethernet).
  • A simple user interface is provided which may be contacted with a telnet under linux. EthNew() initializes the channel. I have to admit that DHCP isnt used: it always crashes if the ethernet port is unpluged (but DHCP works in eboot, I cant explain this). The thread Ethernet listens to any incoming telnet request and provides a set of commands like status, help, set output ports to fix values...
  • msg_P() handles all print-messages. It forks them to V24 and ethernet, and it stores important messages into a fifo which will be displayed on the next telnet-session.
  • a watchdog thread reboots if the main thread hangs
  • hint: I still dont understand how to assign memory to the threads. too few heap results of course in a crash, but to mush also. No indication was available, and I failed to get NutTrace operating. The current values works, for now!
  • HausMain.c: in future I'll provide the code for my house-Ethernut, that controls all heating devices and an LCD-terminal.
  • Example

    A plot of the measured temperatures in my solarthermal facility is here.
    My Ethernut is connected to a lot of dallas devices. This is a graph of all dallas temperate-sensors in my house:


    This shows the used heating power for my house:

    I started calculating this power in May 2006.
    These graphs are of course generated on my linux-PC, based on Ethernut-data.

    HW extentions

    I extended the IOpins: