On Tue, Sep 17, 2019 at 10:49 AM bRitch022 <[email protected]> wrote:
>
> Using two MCP23S17 I/O expanders via SPI1 with CS0 P9.28 and CS1 P9.42.
> I am initializing each chip separately and doing a read immediately after, 
> which produces the expected data. However, if I go back to read the first 
> chip after initializing the second chip, the data is skewed and doesn't read 
> the first chip correctly. This happens even if I swap the order that the 
> chips are initialized -- whichever one was initialized first ends up with 
> skewed data.
>
> Software or kernel issue?

Try again using the MCP23S17 bindings and the pinctrl-mcp23s08 driver:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt

Regards,

-- 
Robert Nelson
https://rcn-ee.com/

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