Uploading file when no SDCard is present returns ERROR:20 Unsupported or invalid g-code command about fluidnc HOT 2 CLOSED

To clarify a little further, this only occurs when no SD Card/SPI is defined in the config file. Having an actual SD Card module connected will indicate whether a card is inserted into the module or not - which is what I expected to see when no SD Card was defined. I still received the same weird errors, however, when I had the module connected to 3.3v - turns out it needed 5v instead, which cleared the errors up, but thought this would be helpful information.

from fluidnc.

Direct detection of card insertion only works if the Card Detect pin is connected to a GPIO. On many controllers that support FluidNC and Grbl_Esp32, that pin is unconnected. In that case, the only way to determine card presence is to try and read the card, which is a fairly expensive operation because of the need to allocate substantial amounts of memory for the data structures that the filesystem uses, and to read numerous data blocks into those data structures. It can be particularly expensive for large capacity SD cards where the data structures are large. It is prone to failure if there are card or filesystem problems.

from fluidnc.