Commit c785d359 authored by g3gg0's avatar g3gg0
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QEMU readme: GPIO section update

--HG--
branch : qemu
parent 7800ecfdd984
......@@ -222,13 +222,13 @@ GPIO ports
''''''''''
These work much like the I/O ports on a Raspberry Pi or Arduino —
switches that you can turn on and off from software (outputs)
or whose state (on or off) can be read by the processor (inputs).
signal lines that you can switch high or low from software (outputs)
or whose input state (high or low) can be read by the processor (inputs).
__ `WriteProtect switch`_
Example: the SD card LED is driven by a GPIO output (by writing to a GPIO register).
The `write-protect switch`__ state is read from a GPIO input (by reading another register).
Example: the SD card LED is driven by a GPIO output (by setting specific bits within the GPIO's register).
The `write-protect switch`__ state is read from a GPIO input (by reading back other bits).
Events from `hot-pluggable devices`__ (USB, external monitors, microphone etc) are usually detected
by reading some GPIO registers in a loop (but they may as well expect interrupts, e.g. ``MICDetectISR``).
......@@ -236,7 +236,7 @@ __ `HotPlug events`_
GPIO ports are also used as `chip select <https://en.wikipedia.org/wiki/Chip_select>`_ signals
for various hardware devices that use the SPI protocol (examples below),
or hardwired to `secondary processors`_ for communication purposes.
or as signalling lines to `secondary processors`_ for communication purposes.
Usual register values for driving GPIO ports: ``0x46/0x44``, ``0x138800/0x838C00``, ``0xD0002/0xC0003``.
More details `on the wiki <http://magiclantern.wikia.com/wiki/Register_Map#GPIO_Ports>`_.
......
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