Didn't you argue you for having a HAL above the module layer earlier..? Wouldn't that mean that *any* chassis would be useless to you?
It's you who suggested that card creator can create HAL himself over SPI bus, suggesting that DIB is nothing more than just physical and electrical definition of backplane.
Bus is more than that. W/o higher level API and good software indeed it is more or less useless.
I did not say anything about HAL, I said - you have to abstract hardware. Control software shall not directly write into ADC or DAC registers. No matter - such function lives in the HAL layer of controller or not. It shall control voltage of power supply, not DAC counts. Module itself shall apply all the compensation and calibration. Those who write control software shall be freed from reading ADC or DAC chip datasheets and those who are good doing electronics, shall be freed from coding anything else than MCU they know.
What would a chassis have to bring to the table to be useful for you?
Chassis appealing to me could be cost-optimized
Keysight U2781A. Definitely with low-speed USB-less card support we are talking here for a while. It shall have quick & easy learning curve for those creating new/own cards. Like Arduino of instrumentation
Chassis alone will not work, it shall be whole ecosystem of affordable, easy DIY instrumentation.
Reference hw/sw design of few typical cards shall be available, as well as "card SDK". Would be supercool if AVR or even Arduino-based cards are shown as examples. I would like stm32-series, but do not insist on that. No need to create very complex
instrumentation API. It's enough to create
communication API for instruments. Host communications could be very simplified like sendvariable(char *name, double value); senddataarray(char *name, double *pdata, int size). Receive functions - just typical function callbacks, registered by variable name. Obviously card can have other (optional) modes of communication such as SCPI.
Anything else I need (~30 trigger signals, analog routing, fast LVDS connections) is probably outside the scope of this project
What about extension bus for hi-end features? Cards are wide enough. You can put Two connectors on advanced cards, one on standard version cards.