It may be obvious to the rest of the world, but in order to get the ADC to operate in Discontinuous Mode, you must also select Scan Mode. This was Not obvious to me from either the comments in the HAL or the reference manual.
The SCAN bit in CR1 apparently makes the ADC scan through the channel list/ranks.
The DISCEN bin in CR1 apparently indicates that the scanning will be interrupted part way through the list and require another trigger to continue.
Without the SCAN bit set, the first channel in the list is sampled repeatedly. The list is not "scanned".
I'm using an STM32F429 on a Nucleo development board.
