FTDI GPIOs via sysfs

About

It is possible to export some pins of FTDI chips as GPIOs in sysfs, so that they are accessible on the shell.

Warning

I do not support the policy of FTDI to brick counterfeiting ICs via their closed-source Windows driver. Please do not use Microsoft Windows, and use only open source drivers that anybody can modify and inspect. This patch was possible because the source code for the driver is freely available. Now you understand why freedom matters.

Help

If you want to help and have some FTDI adaptors, I am interested to know if you managed to get GPIOs over sysfs working. Please send me an email with the model of the board, the pins available as GPIOs, and the voltage output.

Kernel patch

The kernel patch is here: https://lkml.org/lkml/2014/6/9/406
Here in plain text: https://lkml.org/lkml/diff/2014/6/9/406/1

I patched my 3.16 kernel with it (patch -p1 < ftdi-gpio.patch).

JTAGkey Tiny

amontec-jtagkey-tiny-nogpio.jpg

The JTAGkey Tiny is a FT2232C, you can export 8 GPIOS:

root@sabayon /sys/class/gpio [70]# echo 248 > export 
root@sabayon /sys/class/gpio [71]# l
total 0
--w------- 1 root root 4096 Oct  7 22:57 export
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio248 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio248
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio249 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio249
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio250 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio250
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio251 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio251
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio252 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio252
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio253 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio253
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio254 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio254
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpio255 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpio255
lrwxrwxrwx 1 root root    0 Oct  7 22:57 gpiochip248 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.1/ttyUSB0/gpio/gpiochip248
--w------- 1 root root 4096 Oct  7 22:55 unexport

You have to change the direction to be able to change the value:

root@sabayon /sys/class/gpio [95]# echo out > gpio252/direction 
root@sabayon /sys/class/gpio [96]# cat gpio252/value 
0
root@sabayon /sys/class/gpio [97]# echo 1 > gpio252/value 
root@sabayon /sys/class/gpio [98]# cat gpio252/value 
1

The driver is actually ignoring the JTAG pins, and treating them as GPIOs:

[  121.121077] usb 6-1: new full-speed USB device number 2 using uhci_hcd
[  121.317060] usb 6-1: New USB device found, idVendor=0403, idProduct=cff8
[  121.317066] usb 6-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  121.317070] usb 6-1: Product: Amontec JTAGkey
[  121.317074] usb 6-1: Manufacturer: Amontec
[  121.317077] usb 6-1: SerialNumber: T1QSEW77
[  121.324121] usb 6-1: Ignoring serial port reserved for JTAG

I am currently unable to identify any of those GPIO pins!

Arduino Duemilanove

The Duemilanove has an FTDI FT232R, lsusb -v gives:

  idVendor           0x0403 Future Technology Devices International, Ltd
  idProduct          0x6001 FT232 USB-Serial (UART) IC
  bcdDevice            6.00
  iManufacturer           1 FTDI
  iProduct                2 FT232R USB UART

It is also possible to get 8 GPIOs, but I identified only 6 of those, 4 of the X3 connector (they are accessible if you solder a 4 pins header on X3, see this japanese webpage) and 2 on TX RX:

duemilanove-x3-connector.jpg

Those pins are in 5V, but you could get them in 3.3V if you build my special USB cable in order to run the Duemilanove in 3.3V.

Moderndevice BUB1

On the Moderndevice BUB1 (based on a FT232R) on I managed to identify 7 pins out of the 8 exported, those are: RX, TX, RTS, RI, DSR, DCD, CTS. You can actually choose the voltage you want out of those pins (3.3V or 5V) if you play with the jumper.

USB_BUB.jpg

Freaduino v1.0

freaduino.jpg

Freaduino is also based on a FT232RL. I was unable to detect any GPIOs. The board is unusable for that purpose, even with the main chip disabled (RST connected to GND).

MicroFTX

The MicroFTX is based on the FT230XQ. Jim Paris (the creator of the board) has tested the patch and it works fine, as expected. 8 GPIOs show up and 4 are usable. The first four GPIOs correspond to the TX, RX, RTS, and CTS pins, in that order.

microftx-quarter.jpg

And the four CB0/CB1/CB2/CB3 pins are currently not usable as GPIOs:

bottom-smaller.png

FTDI UMFT230XB

I bought this dongle based on the FT230XQ chip at Farnell.

Lsusb says:

Bus 006 Device 002: ID 0403:6015 Future Technology Devices International, Ltd Bridge(I2C/SPI/UART/FIFO)
FTDI-UMFT230XB-01.jpg

RX is gpio249, TX is gpio248, RTS is gpio250, CTS is gpio251. I have to investigate on how to use CB0/CB1 as GPIOs, probably by changing their values in the EEPROM.

Links