mraa  1.8.0
Low Level Skeleton Library for Communication on GNU/Linux platforms
FTDI FT4222H

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. You need the latest version for the GPIO to work.

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.

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:

Output from 'mraa-gpio list' would be as follows:

1 512 IGPIO0/SCL0: GPIO I2C
2 513 IGPIO1/SDA0: GPIO I2C
3 514 INT-GPIO2: GPIO
4 515 INT-GPIO3: GPIO

When an I2C GPIO expander is present, the pins on the expander will appear after the 4 FT4222H GPIO pins (i.e. starting at physical pin #4, logical pin #516).

1 512 IGPIO0/SCL0: GPIO I2C
2 513 IGPIO1/SDA0: GPIO I2C
3 514 INT-GPIO2: GPIO
4 515 INT-GPIO3: GPIO
5 516 EXP-GPIO0: GPIO
6 517 EXP-GPIO1: GPIO
7 518 EXP-GPIO2: GPIO
8 519 EXP-GPIO3: GPIO
9 520 EXP-GPIO4: GPIO
10 521 EXP-GPIO5: GPIO
11 522 EXP-GPIO6: GPIO
12 523 EXP-GPIO7: GPIO

If a PCA9545 I2C switch is detected an extra four I2C busses will appear, representing the four downstream busses. Output from 'mraa-i2c list' would be as follows:

1 Bus 512: id=00 type=ft4222 default
2 Bus 513: id=01 type=ft4222
3 Bus 514: id=02 type=ft4222
4 Bus 515: id=03 type=ft4222
5 Bus 516: id=04 type=ft4222

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.

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:

1 FTDI4222=ON
2 USBPLAT=ON