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Documentation/rtl8730e: document the I2C master buses

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Add a Features bullet and an "i2c" configuration section to the
RTL8730E EVB board page describing I2C0-2 as /dev/i2c0-2, the pads the
board table registers and the i2ctool scan command, following the
pke8721daf board format.

Note the two pad constraints that are specific to this chip: a pad
reaches exactly one I2C controller (unlike the GPIO and UART
crossbars), and the pads inside the analogue audio ranges are driven by
the codec and cannot carry I2C.

Signed-off-by: dechao_gong <dechao_gong@realsil.com.cn>
Assisted-by: Claude <noreply@anthropic.com>
This commit is contained in:
dechao_gong 2026-10-08 18:52:07 +08:00 • committed by Alan C. Assis
parent 4e6ad4fb56
commit b7069dc376
1 changed files with 19 additions and 0 deletions
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19
Documentation/platforms/arm/rtl8730e/boards/rtl8730e_evb/index.rst
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@ -38,6 +38,8 @@ Supported in this NuttX port:
* General-purpose UARTs exposed as ``/dev/ttySN`` serial devices, driven
through the SDK fwlib ROM layer (the LOG-UART owns the console and
``/dev/ttyS0``)
* I2C master buses exposed as ``/dev/i2cN`` character devices, driven in
polling mode through the SDK fwlib register layer
* littlefs persistent storage mounted at ``/data`` (a dedicated SPI NOR flash
partition), backing the Wi-Fi key-value store
* Wi-Fi station and SoftAP through the ``wapi`` tool
@ -98,6 +100,23 @@ The line format can be changed at runtime through ``tcsetattr()`` (the config
enables ``CONFIG_SERIAL_TERMIOS``). UART3 is reserved for Bluetooth and is not
exposed by the driver.
i2c
---
Minimal NSH with the I2C master driver and the ``i2ctool`` (``system/i2c``)
enabled (no Wi-Fi). The board registers its I2C controllers from a table (see
``boards/arm/rtl8730e/rtl8730e_evb/src/rtl8730e_i2c.c``): I2C0 at
``/dev/i2c0`` on PA10/PA9, I2C1 at ``/dev/i2c1`` on PA4/PA3 and I2C2 at
``/dev/i2c2`` on PB11/PB10 (SCL/SDA). Edit that table -- controller and
SCL/SDA pads -- to match a board's wiring; the pads use the same
``AMEBA_PA()`` / ``AMEBA_PB()`` encoding as the GPIO table and are muxed to
the I2C function through the SDK ROM. Unlike the GPIO and UART crossbars, a
pad reaches exactly one I2C controller, and pads the audio codec drives
cannot be used. The I2C bus is open-drain, so fit external pull-ups on
SCL/SDA. Probe a bus with the tool::
nsh> i2c dev -b 0 0x03 0x77 # scan /dev/i2c0 for devices
Wi-Fi
=====