[TriEmbed] Raspberry Pi & Port Expanders

[Ken]

I think those have kernel drivers that would allow you to map them so the 
would look just like regular gpio, to the /sys interface. You would either 
have to add a device entry to map the i2c to gpio device driver in the board 
init file (and rebuild the kernel) or add it in device tree, not sure which 
method the pi supports or which would be easier.
The initial pi setup would be harder, but programming in user space it would 
look the same as the other gpio on the pi.

-----Original Message----- 
From: Grawburg via TriEmbed
Sent: Monday, November 09, 2015 9:22 AM
To: Triangle Embedded Devices
Subject: [TriEmbed] Raspberry Pi & Port Expanders

as many of you already know I'm a big fan of using an I/O port expander 
(MCP23017 or MCP23008) when I'm working with anything that uses voltage 
other than 3.3 VDC. I want to make sure the Pi is fully isolated from the 
devices.  I realize that the Python coding is a bit more involved when using 
an I2C device and that it doesn't currently run on Python 3. I just think 
the trade-off with protecting the Pi is worth it.  Now, here's my question: 
Is there a situation when I should not use an I2C chip, keeping in mind the 
projects I'm dealing with are, by most standards, relatively basic?

At tonight's meeting I'll have part of my pipeline valve and pump project 
that is using a single MCP23017 because I need more than 8 I/O pins. If 
there is an interesting alternative to the I2C I'd like to know about it.


Thanks,
Brian Grawburg





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