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Posts: 3,074 | Thanked: 12,960 times | Joined on Mar 2010 @ Sofia,Bulgaria
#22
Originally Posted by wpwrak View Post
We have a new white paper ! This one discusses IO expanders:

http://neo900.org/stuff/papers/iox.pdf

An IO expander is a chip that connects to the CPU (in our case via I2C) and provides a number of IO ports. Neo900 will need IO expanders because the CPU doesn't have quite enough pins for all the signals. As an added bonus, IO expanders can also lower the number of signals that have to pass between UPPER and LOWER.

This specific version is at
http://neo900.org/stuff/papers/iox-20160622.pdf

The source can be found at
https://neo900.org/git/?p=misc;a=tree;f=iox

- Werner
Please consider evaluating if gpios on the io extender should have wake-up capability, as that will affect power usage etc.

"The two system-wide I2C busses in Neo900 operate at 400 kHz (I2C#2) and 100 kHz (I2C#3)." - I doubt this is correct, i2c1 should operate on 2.2MHz, at it is used to control twl4030 regulators (SmartReflex that is).

Also, IR diode on N900 is not driven by a simple gpio, but through PWM output. If TX diode on Neo900 is going to use the same, then it cannot be attached to iox.

In addition, twl4030 have 18 GPIOs, are all of them used?
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720p video support on N900,SmartReflex on N900,Keyboard and mouse support on N900
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