acassis commented on code in PR #18951:
URL: https://github.com/apache/nuttx/pull/18951#discussion_r3295253768
##########
Documentation/platforms/sim/sim_ft2232h_gpio.rst:
##########
@@ -0,0 +1,218 @@
+=======================================
+Sim FT2232 GPIO Driver (Using libftdi1)
+=======================================
+
+Overview
+========
+
+The NuttX simulation (sim) already has a GPIO Chip driver that provides a
mechanism use GPIO to control external devices. However that solution depends
on having a driver to Linux side and that adds more overhead.
+
+This FT2232H driver allows a direct use of libftdi1 to control up to 8 GPIOs.
+
+This driver is particularly useful for:
+
+- Testing GPIO-based applications in a simulated environment with real hardware
+- Interfacing with USB-to-GPIO adapters from NuttX simulation
+- Developing and debugging GPIO drivers without dedicated embedded hardware
+
+Host Prepare
+============
+
+Preparation required on the host side:
+
+- Hardware module required: FT2232H module like the CJMCU-2232HL module
+- A udev rule on Linux side to avoid using the FT2232H as USB/Serial:
+
+.. code-block:: console
+
+ $ cat /etc/udev/rules.d/99-ft2232h-d2xx.rules
+ ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6010", ATTRS{product}=="FTDI
Device", MODE="0666"
+
+- The libftdi1-dev installed on your system.
+
+Architecture
+============
+
+The driver consists of two layers:
+
+1. **NuttX Layer** (``sim_ft2232h_ioexpander.c``): Implements the NuttX
``ioexpander_dev_s``
+ interface, providing standard GPIO operations to upper-layer NuttX drivers.
+
+2. **Host Layer** (``sim_ft2232h.c``): Interfaces directly with libftdio1 to
initialize and to provide the functions to control the GPIOs.
+
+::
+
+ +---------------------+
+ | NuttX Application |
+ +---------------------+
+ |
+ v
+ +---------------------+
+ | GPIO Lower Half |
+ | (gpio_lower_half) |
+ +---------------------+
+ |
+ v
+ +---------------------+
+ | sim_ft2232h_ioex...c| <-- NuttX ioexpander interface
+ | (ioexpander_dev_s) |
+ +---------------------+
+ |
+ v
+ +---------------------+
+ | sim_ft2232h.c | <-- Linux host GPIO interface
+ | (host interface) |
+ +---------------------+
+ |
+ v
+ +---------------------+
+ | libftdi1 | <-- Linux library to control FT2232H
+ +---------------------+
Review Comment:
Good suggestion! Done!
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