You got the wires crossed between "lcd dig1" and "lcd dig3" - the labels and pin numbers on either sides seems correct, but the wires do not trace to the right pin - I know..,. minor glitch, but still, it can (and did for me) cause some confusion. ;)
Edit: Should probably point out, that it's in the "858D_RevEng_Schematic.pdf" since you have multiple schematics in here :D

Evaluate if

a) multi-point (e.g. 10 or 20) calibration is feasible & accurate enough
b) non-linear fit on calibration data is OK (might need float variables - slow)

What about different models / clones. Same thermo-couple characteristics?

Hi!

It's not really a problem, because besides that everything works fine, but still:

Most of the time I switch on the station, it simply does the show firmware version and fan test part twice. So after the first fan test the display flickers briefly, shows the version still/again and the fan spins up again. After that the three dashes (or temperature) show and everything works as expected.
About 1/5th of the time the station does only one test.

Any ideas where to look?

I'm using the Youyue 858D+ 20140415 v6.0 board with the ATmega328p and the binary file which is kindly provided here. I also didn't change any settings yet - so everything is set to default.

This is how I flashed the chip (I renamed the file):

avrdude -c usbasp -p atmega328p -v -U lfuse:w:0xE2:m -U hfuse:w:0xDF:m -U efuse:w:0x05:m -U lock:w:0x0F:m

avrdude -c usbasp -p atmega328p -v -e -U flash:w:858d.hex:i

I never used avrdude before, so I post this too, just in case I did something wrong...

The links in README.md's Compiling/Development section don't point to their intended targets. I suspect you meant:

* Use the [Arduino IDE](https://www.arduino.cc/en/Main/Software), make sure you do ISP Upload and _don't_ use the arduino bootloader.
* Use [Atmel Studio 6](http://www.atmel.com/microsite/atmel_studio6/) together with the [VisualMicro Plugin](http://www.visualmicro.com/page/Arduino-for-Atmel-Studio.aspx) for Arduino support, make sure you do ISP Upload and _don't_ use the arduino bootloader.

Hi,

I had "H-E" and changed head gone some years before.
Now it comes back.

It turned out to be a bad ground connection between the two pushbuttons. I soldered a wire between the outer ground pins of the pushbuttons, and it's now working perfectly.

The reason you get the "H-E" is because the negative lead of the thermocouple lead is grounded via the pushbuttons. If there is a break in the ground, the thermocouple is pulled to a higher voltage ( via R31) and the opamp goes into saturation trying to amplify it.
The saturation voltage is about 4V, which the MCU interprets as ~892 deg. Then, after a couple of seconds it goes into error mode.

Anyway, check that the black thermocouple wire is properly grounded. In my case, the problem was intermittent, and showed up when the board flexed (due to pushing buttons).

maybe you can mentioned in your readme

Thanks for your alternative firmware.

Unfortunately I get "RST" roughly every second time I turn on the unit. Moreover, when I set the fan speed to maximum and start the unit I get "FANSPD". Is this expected without the current sens mod?

I'm using your binary and flashed it to a ATMEGA168-20PU with the following command:
avrdude -patmega168 -cstk500v1 -P/dev/ttyUSB0 -b19200 -e -Uefuse:w:0x05:m -Uhfuse:w:0xdd:m -Ulfuse:w:0xe2:m -Uflash:w:2015-02-16__commit-9e3db57f__ATmega168-8MHz-RC-osc__FUSES-0xE2-0xDD-0xFD__V1.37-WDT.hex

Sorry for opening an issue for this, because it's more of a simple question than a problem:

Is the trimmer labeled "CAL" on the front panel used in your firmware at all? It is not mentioned anywhere - so I guess temperature correction is (only) applied by the value in the software settings as described in the docs?