ADC (DMA) overrun error at the fastest sampling speed (STM32F030RC)

[Jim Seymour]

Using ADC with DMA to read a bunch of analog inputs on a STM32F030RC, I am getting an error callback due to an overrun error if I select 1.5 cycles for the sampling time.

Any slower sampling time seems to work OK.

I'm confused about how this error could occur. As I understand it, the ADC runs at 14 MHz. Meanwhile, I'm running the MCU at only 8 MHz. But even so, I'm using the ADC in 12-bit mode, so it's going to take many cycles to read one channel. It seems like the MCU should be able to keep up - even at 8MHz.

Is an overrun in this situation expected?

Thanks.