My current understanding of the problems around the Multislope Precision ADC DIY design and its feasibility is as follows:
1. the real know-how and expertise is in the analog part and in the processes of handling the analog part such you will get the best results
2. the digital part - inguard and outguard - is the simple part. Any modern cheapo 32bitter can do, any cheapo CPLD/FPGA can do, it does not matter. I would be happy to have an MCU with good built in ADC (ie with an external Vref).
The other stuff like display, buttons, power source, usb/232/wifi/ethernet is just a business as usual.
I worked with 8080 asm, Z80 asm, 8051 asm, 68k asm, atmel's asm, pic's asm, but the acceptance of an asm based firmware is pretty low today. Not talking manageability of such a source. People do not work with asm today.
With FPGA/Verilog you do not care on how what asm instruction work, and how many clocks it is long, and how many nops you have to insert to compensate a loop, or how to shift a 24bit word 7bits left, or how to set the portB pin3 and 6.
DIY hw community is C/C++ positive, with more and more emphasis towards programmable logic (because most the tools are free, easy to handle and the small chips are cheap). Verilog/VHDL - ok, that is something people discuss from time to time. Thus the languages are pretty clear.
I would be happy to have a chance to buy a 10x10cm large ADC inguard board, for say XXEuro, with 6.5+digits capability +/-20V input ADC on it, with >1G input impedance, with the 399 on it, with a 10pin connector for +/-25V +/-15V and +5V external floating power sources, a 4pin connector which communicates via opto-isolated UART with "something".
I can flash the board through a 3pin SWD connector (both MCU and FPGA) with a $2 dongle, where the FPGA and MCU there are "standard" C/C++/Verilog supported things. In addition a small I2C flash for calibration params wired to the MCU would be handy on the board.
The FPGA/CPLD bitstream bianary could be put into a C const array easily, and flashed together with the FW into the MCU. Upon reset the MCU loads the FPGA and that's it.
You may have several bitstreams stored in the MCU's memory and you may reconfigure the entire FPGA on the fly within a few milliseconds.
With that $4 combo you may measure every even ADC sample with Jaromir's algorithm, and every odd ADC sample with Kleinstein's algorithm, 25 samples per second (provided the analog part supports such an switch
).
You may put a simple CLI in the MCU, and talk to the board via set of "commands".
That all is easy today. People play with it every day. People run FreeRtos with CLI on the $2 BluePill.
What is not easy is the analog part and the processes around it, imho..