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ftdi_ft4222.md: updated docs with latest info

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Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
This commit is contained in:
Mihai Tudor Panu
2015-12-04 12:30:09 -08:00
committed by Brendan Le Foll
parent ff6b304fd2
commit 92cc9ea176
1 changed files with 30 additions and 7 deletions
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docs/ftdi_ft4222.md
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@@ -5,15 +5,32 @@ The FT4222H is a High/Full Speed USB2.0-to-Quad SPI/I2C device controller. Mraa
supports it as a USB subplatform using the libft4222 library from FTDI which
can be found
[here](http://www.ftdichip.com/Support/SoftwareExamples/libft4222-1.2.1.4.tgz).
You need the latest version for the GPIO to work
You need the latest version for the GPIO to work.
The FT 4222H has 4 configuration modes selected by {DCNF1, DCNF0}. The c hip
configuration mode will determine the number of USB interface s for data stream
s and for GPIOs control. Mraa supports only chip CNFMODE0.
The FT4222H has 4 configuration modes selected by {DCNF1, DCNF0}. The chip
configuration mode will determine the number of USB interfaces for data streams
and for GPIOs control. Mraa supports chip modes CNFMODE0 and CNFMODE3. In
CNFMODE0 the chip can provide either 4 GPIOs and SPI, or 2 GPIOs and I2C
since SCL/SDA are shared with GPIO0/GPIO1. It is possible to change this
selection dynamically by calling the corresponding mraa init functions.
CNFMODE3 on the other hand will only provide SPI or I2C.
Whilst mraa can support custom board in CNFMODE0 (support for other mode is
welcome!) there may be some work to be done. We test using FTDI's UNFT4222EV
reference board. More detail on this board can be found
By default, both modes start with I2C enabled and the driver will scan for
known GPIO expanders on the I2C bus when the FT4222H is initialized.
Supported GPIO expanders:
* PCA9672
* PCA9555
* PCF8575
When a GPIO expander is present, the pins on the expander will be initialized
first and the 4 GPIO pins on the FT4222H are appended after.
Please note that some mraa features might not be fully implemented yet and they
are still under development (e.g. SPI replacement functions).
We tested the module using FTDI's UMFT4222EV reference board. More details on
this board can be found
[here](http://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_UMFT4222EV.pdf).
Interface notes
@@ -22,3 +39,9 @@ Interface notes
You will need to unload all ftdi kernel modules for libft4222 to work
correctly. You will also have to compile mraa with FT4222 support which may not
be enabled by default.
The cmake options to build this driver are:
~~~~~~~~~~~~~
FTDI4222=ON
USBPLAT=ON
~~~~~~~~~~~~~