PL2303 HXD GPIOs

About

I was hunting for many days for a USB dongle that would provide GPIO entries in the form of entries in /sys/class/gpio.

I found the Oneping.com.tw PL2303 breakout board with the chip PL2303 HXD (or HX revD), which has nice 2.54mm pins for 4 GPIOs (GP0, GP1, GP2, GP3). According to the datasheet, there seems to be 4 auxiliary GPIOs (so 8 GPIOs in total), but there is no documentation on how to use them.

Oneping produces 3 different versions of the board for different GPIO output voltages: 1.6V, 3.3V, 5V. I own the 3.3V version.

pl2303-gpio-oneping.jpg

Kernel patch

Wang YanQing wrote a patch (local copy pl2303-gpio-sysfs.patch) to recent kernels (this is one is tested against 3.16, 4.1) in order to expose those GPIOs in /sys/class/gpio.

First, you have to install or to download the kernel sources of your kernel, if you install them via your distribution, they will be put on /usr/src/:

root@sabayonx86-64 /usr/src [21]# equo install "sys-kernel/sabayon-sources-4.1.12"
╠  @@ Calculating dependencies...
╠  ## [N] [sabayon-weekly] sys-kernel/sabayon-sources-4.1.12|0
╠  @@ Packages needing to be installed/updated/downgraded: 1
╠  @@ Packages needing to be removed: 0
╠  @@ Download size: 0b
╠  @@ Used disk space: 558.3MB
╠  @@ You need at least: 770.3MB of free space
╠  ::: >>>  (1/1) 1 package
╠    ## Downloading: 1 package
╠    ## ( mirror #1 ) [sys-kernel:sabayon-sources-4.1.12.749d89a47c204e21eba4525de38e3042e896f6d4~0.tbz2] @ http://na.mirror.garr.it
╠   ## Aggregated download: 1 item
╠    # [1] na.mirror.garr.it => sys-kernel:sabayon-sources-4.1.12.749d89a47c204e21eba4525de38e3042e896f6d4~0.tbz2
╠    ## Checking package checksum...
╠    ## ( mirror #1 ) [sys-kernel:sabayon-sources-4.1.12.749d89a47c204e21eba4525de38e3042e896f6d4~0.tbz2] success @ http://na.mirror.garr.it
╠  +++ >>>  (1/1) sys-kernel/sabayon-sources-4.1.12
╠    ## Unpacking: sys-kernel:sabayon-sources-4.1.12.749d89a47c204e21eba4525de38e3042e896f6d4~0.tbz2
root@sabayonx86-64 /usr/src [27]# ls -lha
total 36K
drwxr-xr-x  6 root root 4.0K Feb 25 18:46 .
drwxr-xr-x 21 root root 4.0K Feb 25 18:42 ..
-rw-r--r--  1 root root    0 Nov 19  2005 .keep
lrwxrwxrwx  1 root root   19 Feb 25 18:45 linux -> linux-4.1.0-sabayon
drwxr-xr-x 25 root root 4.0K Feb 25 18:44 linux-4.1.0-sabayon
-rw-r--r--  1 root root 9.3K Sep  4  2014 pl2303-gpio-sysfs.patch
drwxr-xr-x  7 root root 4.0K Oct  8  2014 rpm
drwxr-xr-x  4 root root 4.0K Feb  1 15:02 spl-0.6.5.3
drwxr-xr-x  4 root root 4.0K Feb  1 15:02 zfs-0.6.5.3

I can download the patch here:

root@sabayonx86-64 /usr/src [29]# wget http://zoobab.wdfiles.com/local--files/pl2303hxd-gpio/pl2303-gpio-sysfs.patch
--2016-02-25 18:48:38--  http://zoobab.wdfiles.com/local--files/pl2303hxd-gpio/pl2303-gpio-sysfs.patch
Resolving zoobab.wdfiles.com... 54.165.29.53
Connecting to zoobab.wdfiles.com|54.165.29.53|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 9517 (9.3K) [text/x-diff]
Saving to: ‘pl2303-gpio-sysfs.patch’

pl2303-gpio-sysfs.patch         100%[========================================================>]   9.29K  --.-KB/s   in 0.002s 

2016-02-25 18:48:39 (5.64 MB/s) - ‘pl2303-gpio-sysfs.patch’ saved [9517/9517]

root@sabayonx86-64 /usr/src [30]# ls -lha
total 36K
drwxr-xr-x  6 root root 4.0K Feb 25 18:48 .
drwxr-xr-x 21 root root 4.0K Feb 25 18:42 ..
-rw-r--r--  1 root root    0 Nov 19  2005 .keep
lrwxrwxrwx  1 root root   19 Feb 25 18:45 linux -> linux-4.1.0-sabayon
drwxr-xr-x 25 root root 4.0K Feb 25 18:44 linux-4.1.0-sabayon
-rw-r--r--  1 root root 9.3K Sep  4  2014 pl2303-gpio-sysfs.patch
drwxr-xr-x  7 root root 4.0K Oct  8  2014 rpm
drwxr-xr-x  4 root root 4.0K Feb  1 15:02 spl-0.6.5.3
drwxr-xr-x  4 root root 4.0K Feb  1 15:02 zfs-0.6.5.3
root@sabayonx86-64 /usr/src [31]#

I had to add a symlink from "a" to "linux":

root@sabayonx86-64 /usr/src [31]# ln -s linux a
root@sabayonx86-64 /usr/src [32]# l
total 28
lrwxrwxrwx  1 root root    5 Feb 25 18:49 a -> linux
lrwxrwxrwx  1 root root   19 Feb 25 18:45 linux -> linux-4.1.0-sabayon
drwxr-xr-x 25 root root 4096 Feb 25 18:44 linux-4.1.0-sabayon
-rw-r--r--  1 root root 9517 Sep  4  2014 pl2303-gpio-sysfs.patch
drwxr-xr-x  7 root root 4096 Oct  8  2014 rpm
drwxr-xr-x  4 root root 4096 Feb  1 15:02 spl-0.6.5.3
drwxr-xr-x  4 root root 4096 Feb  1 15:02 zfs-0.6.5.3

Now apply the patch:

root@sabayonx86-64 /usr/src [33]# patch -p0 < pl2303-gpio-sysfs.patch 
(Stripping trailing CRs from patch; use --binary to disable.)
patching file a/drivers/usb/serial/Kconfig
Hunk #1 succeeded at 519 (offset 3 lines).
(Stripping trailing CRs from patch; use --binary to disable.)
patching file a/drivers/usb/serial/pl2303.c
Hunk #2 succeeded at 32 with fuzz 2 (offset -102 lines).
Hunk #5 succeeded at 246 (offset 3 lines).
Hunk #6 succeeded at 478 (offset 3 lines).
Hunk #7 succeeded at 507 (offset 3 lines).
Hunk #8 succeeded at 521 (offset 3 lines).

Then go to the linux directory, and run "make menuconfig":

The go to "-> Device Drivers -> USB support -> USB Serial Converter support -> USB Prolific 2303 Single Port Serial Driver -> USB Prolific 2303 Single Port GPIOs support".

pl2303-gpio-sysfs-make-menuconfig.png

When you will save, it will have this block in the .config file:

+config USB_SERIAL_PL2303_GPIO
+       bool "USB Prolific 2303 Single Port GPIOs support"
+       depends on USB_SERIAL_PL2303 && GPIOLIB
+       ---help---
+         Say Y here if you want to use GPIOs on PL2303 USB Serial single port
+         adapter from Prolific.
+
+         It supports 2 dedicated GPIOs on PL2303HXA, 4 dedicated GPIOs on
+         PL2303HXD and PL2303RA currently.
+         If unsure, say N.

Now, you can compile all the serial modules:

root@sabayonx86-64 /usr/src/linux [15]# make SUBDIRS=drivers/usb/serial modules -j5
  CC [M]  drivers/usb/serial/usb-serial.o
  CC [M]  drivers/usb/serial/generic.o
  CC [M]  drivers/usb/serial/bus.o
  CC [M]  drivers/usb/serial/aircable.o
  CC [M]  drivers/usb/serial/ark3116.o
  CC [M]  drivers/usb/serial/belkin_sa.o
  CC [M]  drivers/usb/serial/ch341.o
  CC [M]  drivers/usb/serial/cp210x.o
  CC [M]  drivers/usb/serial/cyberjack.o
  CC [M]  drivers/usb/serial/cypress_m8.o
  CC [M]  drivers/usb/serial/digi_acceleport.o
[...]

You will then have a pl2303.ko compiled:

root@sabayonx86-64 /usr/src/linux/drivers/usb/serial [20]# ls -1 pl*.ko
pl2303.ko

Try to unload/load it:

root@sabayonx86-64 /usr/src/linux/drivers/usb/serial [26]# rmmod pl2303; insmod ./pl2303.ko ; lsmod | grep pl2303
pl2303                 11963  0
usbserial              25891  1 pl2303

You will then see in /sys/class/gpio that there is now a gpiochip available:

root@sabayon /sys/class/gpio [2]# l
total 0
--w------- 1 root root 4096 Sep  4 10:25 export
--w------- 1 root root 4096 Sep  4 10:25 unexport
root@sabayon /sys/class/gpio [3]# l
total 0
--w------- 1 root root 4096 Sep  4 10:25 export
lrwxrwxrwx 1 root root    0 Sep  4 10:26 gpiochip252 -> ../../devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1:1.0/gpio/gpiochip252
--w------- 1 root root 4096 Sep  4 10:25 unexport

You can export the 4 GPIOs with echo:

root@sabayon /sys/class/gpio [22]# echo 252 > export
root@sabayon /sys/class/gpio [23]# echo 253 > export
root@sabayon /sys/class/gpio [24]# echo 254 > export
root@sabayon /sys/class/gpio [25]# echo 255 > export
root@sabayon /sys/class/gpio [26]# l
total 0
--w------- 1 root root 4096 Sep  4 16:02 export
lrwxrwxrwx 1 root root    0 Sep  4 16:01 gpio252 -> ../../devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1:1.0/gpio/gpio252
lrwxrwxrwx 1 root root    0 Sep  4 16:02 gpio253 -> ../../devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1:1.0/gpio/gpio253
lrwxrwxrwx 1 root root    0 Sep  4 16:02 gpio254 -> ../../devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1:1.0/gpio/gpio254
lrwxrwxrwx 1 root root    0 Sep  4 16:02 gpio255 -> ../../devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1:1.0/gpio/gpio255
lrwxrwxrwx 1 root root    0 Sep  4 15:59 gpiochip252 -> ../../devices/pci0000:00/0000:00:1a.0/usb3/3-1/3-1:1.0/gpio/gpiochip252
--w------- 1 root root 4096 Sep  4 15:59 unexport

Toggling the pins on the shell works, but I have to test the toggling speed with a C program.

I am noting a change in voltage from 0V to 3.3V with this:

root@sabayon /sys/class/gpio [32]# while true; do sleep 1; echo 0 > gpio252/value; sleep 1; echo 1 > gpio252/value; done

Which confirms that it is working as expected.

Test with an HXA

I had an RS232 (using 12V) adaptor laying around, tried it as well, GP1 and GP0 were exposed:

root@sabayon /sys/class/gpio [26]# l
total 0
--w------- 1 root root 4096 Sep  4 18:35 export
lrwxrwxrwx 1 root root    0 Sep  4 18:35 gpio254 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-2/6-2:1.0/gpio/gpio254
lrwxrwxrwx 1 root root    0 Sep  4 18:35 gpio255 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-2/6-2:1.0/gpio/gpio255
lrwxrwxrwx 1 root root    0 Sep  4 18:34 gpiochip254 -> ../../devices/pci0000:00/0000:00:1d.0/usb6/6-2/6-2:1.0/gpio/gpiochip254
--w------- 1 root root 4096 Sep  4 18:34 unexport

But I could not change the status of the pin:

root@sabayon /sys/class/gpio [22]# echo 1 > gpio255/value 
root@sabayon /sys/class/gpio [23]# cat gpio255/value 
0

I don't know why…

I also tried with a chinese clone (small chip covered with some black paste), got the same error, could export the 2 GPIOs, but could not write to them.

Android app and USB sniffing

The android app PL2303GPIOActivity.apk provides an GUI to toggle the 4 GPIO pins and the 4 auxiliary pins (this is a feature NOT documented anywhere). The app only works on some tablet versions of Android. After fighting with different tablets which supports OTG, I decided to give Android-x86-4.4-r1 a shot on my Lenovo X200 laptop, and it works like a charm. The only problem is that the kernel does not have support for usbmon, so I will need to recompile the whole thing to be able the sniff the USB packets. Stay tuned!

Todo

  • Find a decent and simple speed tester for sysfs gpio pins
  • Test avrdude and urjtag with GPIO cable support
  • Blink a LED
  • Speed comparison with RaspberryPi GPIO bitbanging
  • Order some chips PL2303TB with 12 GPIOs
  • Find out how to disable the RI/DCD/DSR/CTS pins in order to use them as GPIOs (look at the source code of the android app)

Other chips

Cypress

Cypress has also pushed a patch to support 12 GPIOs over USB with the CYUSBS234. A devboard CYUSBS232 is available at Mouser, including the standalone chip CY7C65213-28PVXI in SOP28 format.

Sparkfun sells now a nice breakout board with this Cypress chip.

FTDI

Just discovered this patch posted in June on the LKML: https://lkml.org/lkml/2014/6/9/406 . It is not merged in mainline because kernel guys are nagging about it, so I am trying it now on the ftdi-gpios-sysfs page.

Links

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