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[fullmoon6661]

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[dmendesf]

Use 2 SPIs, one as master and other as a slave. Connect clock and CS together. Use master SPI to drive adc and get one datastream. Slave SPI gets the other datastream automagically.

[pcprogrammer]

The 2 spi setup dmendesf gave is the way to go, but have you thought about what you are going to do with 2 times 16bit 1Msps of data coming into the STM32F103?

You need DMA to get the samples into the memory to not burden the CPU, but there is not a lot of memory to store the samples.

And even though it is a quick MCU then do processing on the samples and spit them out to some other system is also a bit of a load. Sure it can be done but not with sustained data.

With USB I managed to get a single channel of sustained 16bit 100Ksps to stream to a PC. Needed to write my own USB driver under linux to make it work.