Marlin bugfix-2.0.x and REARM - MAX6675 Problem
March 16, 2020 05:26PM
Hello all ... I´m new in this forum.
I have problems to get MAX6675 to work on the following configuration:
latest Marlin bugfix-2.0.x FW on REARM board with Ramps 1.6 addon ... REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER is connected and enabled, SDSUPPORT is diabled.
After turning on the power, the bootscreen shows up, then it shows a broken "status" screen and it is beeping, followed by a constant tone and a message on the LCD "temp. on E1 to high ... Printer stopped".
Only one Hot-End is enabled.
I searched the whole code, but couldn't find the place where the SPI pins for the MAX6675 are defined. In my opinion I have tested all SPI pins that can be found in the REARM pinout. Error also happens when MAX6675 is not connected at all.
I also tried to enable SDSUPPORT but the problem remains. With LCD and SDSUPPORTdisabled no connection to the board is possible.

I hope someone can give me a hint :-)

BR Andy
Re: Marlin bugfix-2.0.x and REARM - MAX6675 Problem
March 16, 2020 06:56PM
Same problem with Marlin 2.0.5 with Max6675 connected to P0_15 and P0_17 for SCK and SO :-(
Re: Marlin bugfix-2.0.x and REARM - MAX6675 Problem
March 20, 2020 11:17AM
The MAX6675 chips are not the problem, i have tested them with an arduino nano. They work fine also on 3.3V.

Does no one have any idea how to fix this problem?
And does nobody have a MAX6647 running on a ReARM board?
Re: Marlin bugfix-2.0.x and REARM - MAX6675 Problem
March 20, 2020 11:55AM
There is a setting to ignore temp reading for a while till they settle after boot, and I suspect you need this.
But I cant remember the keyword (and it is most frustrating)
Re: Marlin bugfix-2.0.x and REARM - MAX6675 Problem
March 20, 2020 12:06PM
Found it

set #define BOGUS_TEMPERATURE_GRACE_PERIOD 2000 in your Configuration.h

Edited 1 time(s). Last edit at 03/20/2020 12:08PM by Dust.
Re: Marlin bugfix-2.0.x and REARM - MAX6675 Problem
March 20, 2020 12:47PM
@Dust Thanks for your tip, unfortunately the setting causes a delay of the problem by about two seconds (max. temp. error)
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