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STM32F4 19 bit SPI Data Read

Question asked by roofie01 on Feb 3, 2016
Latest reply on Feb 4, 2016 by John F.
Hi,

I am using an LTC2433 current sense device that has 3-wire SPI that can operate in several modes. It has a maximum throughput of about 6 reads/second, but since I will be reading it less than 1/second, speed is not an issue.
Because it uses so little power, I could run it in Mode 4, which is continuous conversion. LT describes it as "Internal SCK, 2-Wire I/O, Continuous Conversion". For reference, I've attached a screen cap of the timing diagram from the data sheet. The length of the data packet is 19 bits (in all modes). In this mode CS is tied low to enable continuous conversion.
To transfer, the SDO line from the LT2433 goes from 1 to 0 to indicate the start of the 19 bit data. Also, SCK is toggling as an output in this mode at the internal rate.
Question:
I'm a bit lost on what the most effective way to capture this would be in this mode.

Or...not: just stick to regular SPI. However, with 19 bit data, how does one set up and read with the SPI interface? Would it be set up as 8 or 16 bit?

Thanks for your help!

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