I would like to boot a Rasperry Pi in headless mode and then use a notebook-sized monochrome LCD display attached to the HDMI port as a DIRECT output device, bypassing the OS. In particular, I would like text labels and numeric data to appear in fixed locations on the screen with the ability to regularly update the numeric data by writing to that location from a Python program (this will be a text-based instrument panel for an experimental homebuilt airplane). It seems like a simple and obvious thing to do, but I have been unable to find any clues how to do it. Most references I have found to directly writable LCDs are for 40x2 (or smaller) character displays, whereas I need considerably more real estate for displaying multiple variables simultaneously (possibly some simple graphics too, but I can live without it if necessary).
I would consider an arrangement in which the OS does share the monitor, but only if it can be made to completely disappear after the program is started, ensuring direct and exclusive access to the screen for the aforementioned real-time display.
In the old days working with an IBM/DOS computer, I could control the non-windowed screen display very simply by poking characters or bit data into specific physical memory addresses. I'm basically trying to find a way to achieve equivalent functionality with today's hardware, presumably through a layer of software that knows how to talk to the hardware. Sample pseudocode:
1 open screen device on HDMI port and set any relevant modes
2 specify a starting screen address (row and character no.) and write a N-character string to that location