Peter's electronic projects

USB digital GPIO I/O extender

description

Add general purpose input/output lines to your computer based projects. This circuit is a 12 pin digital GPIO interface using the Microchip PIC18f14k50 microcontroller which connects to an USB host port. The microcontroller is available in through-hole DIP20 and SMD packages, too.
NOTE for beginners: PIC18F14k50 is a general purpose microcontroller which has to be programmed before you can use it in the actual circuit! Please check out this link to learn more.
USB GPIO interfaceUSB GPIO interfaceUSB GPIO interface

Circuit diagram

The device is powered by the USB bus. 12 port bits can be set on a bit-by-bit basis to input or output direction. All LEDs on the schematic are optional, and are only shown for testing the device. You can find the USB connector pinouts at http://pinouts.ws/usb-pinout.html

I can send you pre-programmed microcontrollers or fully assembled, tested boards. If you are interested, contact me


USB digital I/O extender schematic

Controlling the GPIO interface

A computer, any OpenWrt router, Raspberry Pi or other Linux development board with an USB host port can be used to control the GPIO extender. The "controlio" utility runs on all platforms.

Usage: controlio [options] <command> [value]
Control an USB I/O port

-d, --device <vendorid>[:productid]
Select only device(s) with USB vendorid[:productid], default=0x04d8:0xf7c0
-s, --serial <serial number>
Select only the device with the given serial number, default=any
-o, --output <base>
Set output format. Base x=hexadecimal (16), b=binary (2), d=decimal (10), default=x
-v, --verbose
Verbose mode
-V, --version
Show program version
-h, --help
Show usage and help

The commands are:

command line
description
controlio getport
read the digital I/O port states
controlio setdir <n>
set the digital I/O port directions. Use bit 1 to set direction to input, bit 0 to set direction to output
<n> is a 16-bit number
controlio setport <n>
set the digital I/O port output states. Sets all output I/O pins. Use bit value of 1 to set output to HIGH, 0 to set output to LOW
<n> is a 16-bit number
controlio setbit <n>
set the selected digital I/O port output pins to HIGH. Use bit value of 1 to select I/O pins to set
<n> is a 16-bit number
controlio clearbit <n>
set the selected digital I/O port output pins to LOW. Use bit value of 1 to select I/O pins to clear
<n> is a 16-bit number


Numbers for <vendorid>, <productid> and <n> can be given in decimal, hexadecimal or binary format. Hexadecimal numbers are prefixed with '0x', binary numbers are prefixed with '0b'. Command output base can be also set to hexadecimal with switch -ox, decimalwith switch -od or binary with switch -ob.

Mapping of I/O port pins, directions to parameter <n> and buffer output:

controlio getport output
buffer[0]
buffer[1]
I/O pin
RC7
RC6
RC5
RC4
RC3
RC2
RC1
RC0
RB7
RB6
RB5
RB4
-
-
-
-
controlio setport <n>
controlio setdir <n>
controlio setbit <n>
controlio clearbit <n>
bit#7
bit#6
bit#5
bit#4
bit#3
bit#2
bit#1
bit#0
bit#15
bit#14
bit#13
bit#12
bit#11
bit#10
bit#9
bit#8


Examples:

command line example
explanation
controlio setdir 0xffff
set all I/O pins as input
controlio getport
Read the digital I/O port states. The output is 16 bits long, and is shown in the selected base (use the -o command line switch). Output ports usually read back the state they are set to. Input ports read their externally set state.
Command output is:
0xf0ff
controlio -od getport
Read the digital I/O port states. Same as the previous command, but the output is printed in decimal:
61695
controlio -ob getport
Read the digital I/O port states. Same as the previous command, but the output is printed in binary:
0b1111000011111111
controlio setdir 0
set all I/O pins as output
controlio setport 0
set all output I/O pins LOW
controlio setport 12 or
controlio setport 0xc or
controlio setport 0b1100
set the RC2 and RC3 I/O pins HIGH,  other output pins LOW (works only on output pins)
controlio setbit 32768 or
controlio setbit 0x8000 or
controlio setbit  0b1000000000000000
set the RB7 output pin HIGH, don't change other output pins (works only if RB7 is an output pin)
controlio clearbit 4097 or
controlio clearbit 0x1001 or
controlio clearbit 0b1000000000001
set the RB4 and the RC0 output pins LOW, don't change other output pins (works only if RB4 and RC0 are output pins)

Download

Download drivers and utilities for the GPIO board for Windows, for others. The package contains:

bin/device_firmware
the firmware HEX file for the PIC18F14K50 device
bin/host/linux.x86
the Linux controlio utility executable
bin/host/openwrt
the OpenWrt packages for the controlio utility
bin/host/raspberry
Raspberry Pi binaries for the controlio utility
bin/host/win.x86/driver
the drivers for using the GPIO device under Windows
bin/host/win.x86
the Windows controlio.exe utility
src/device_firmware
the C18 source code for the PIC18F14K50 firmware
src/host/openwrt
the source code for building the OpenWrt package
src/host/posix
the source code for building the controlio utility for Linux and other POSIX compatible systems
src/host/python
example code for accessing the GPIO device from python


Previous, obsoleted version with assembly firmware

Installing on the PIC18F14K50 device

Program the bin/device_firmware/usbio.hex file with a Microchip Pickit 2 or Pickit 3 programmer into the chip.

Installing on the host

Linux

  1. install libusb-0.1 with "apt-get install libusb-0.1" or "yum install libusb"
  2. copy bin/host/linux.x86/99-usbio.rules to /etc/udev/rules.d/ - this lets everyone use the device
  3. copy bin/host/linux.x86/controlio to the host
  4. connect the GPIO extender to the USB port

Raspberry Pi

  1. install libusb-0.1 with "apt-get install libusb" on Raspbian or "yum install libusb" on Pidora
  2. copy bin/host/linux.x86/99-usbio.rules to /etc/udev/rules.d/ - this lets everyone use the device
  3. copy bin/host/raspberry/controlio to the host
  4. connect the GPIO extender to the USB port

OpenWrt

  1. install the package for your platform from bin/host/openwrt with "opkg install usbio_2.2-3_<platform>.ipk". This will also install the libusb package if not present
  2. connect the GPIO extender to the USB port

Windows

  1. Extract the contents of the directory usbio-v3.5/bin/host/win.x86
  2. Connect the GPIO extender to the USB port
  3. If your OS is Windows XP or Windows 7:
    the computer will ask for a driver – choose the driver.winxp-7 directory
    Go to step 8.
  4. If your OS is Windows 8 or Windows 10:
    start the Zadig installer found in the driver.win8-10 directory
    The installer is signed by “Akeo Consulting”.
  5. The bottom of the installer window should read "1 device found".
    If it reads "0 devices found" instead, please check the USB connection of the board and repeat from step 4.
  6. Press the “Install driver” button
  7. Wait for the message “The driver was installed successfully” to appear
  8. Start the command line and enter this command:
    controlio -v getport
  9. If the message “Matching device found.” is shown, the driver is operational

Testing

Check operation with "controlio getport". If everything is OK, a 16-bit number read from the I/O port pins is printed. In case of a "No matching device found..." error the GPIO extender is not found. The device is identified by the USB vendorid and productid. Check for the device with lsusb on Linux, cat /proc/bus/usb/devices on OpenWrt or in the device manager on Windows. Use the "controlio -v getport" command for troubleshooting.

Compiling the host side code under Linux

- install a C compiler and the libusb development headers

yum install gcc libusb-devel # for redhat/fedora/pidora
apt-get install gcc libusb-dev # for debian/ubuntu/raspbian

- compile the code

cd src/host/posix/controlio
cc -o controlio controlio.c -lusb

- check operation with the command

./controlio getport

Compiling the host side code for OpenWrt

- install the OpenWrt SDK on a computer
- copy src/host/openwrt/usbio into the package directory
- select the usbio package to be built (Utilities->usbio) from

make menuconfig

- build the usbio package

make package/usbio/compile V=s

Compiling the host side code under windows

- download and install mingw and msys from mingw.org
- copy the file from src/host/posix/controlio/controlio.c to the c:\mingw\msys\1.0\home\<user> directory where <user> is your user name
- download and install libusb-win32 from sourceforge
- copy include/lusb0_usb.h from the libusb package to c:\mingw\msys\1.0\include\usb.h
(if your libusb-win32 version is 1.2.4 or older, then copy include/usb.h to c:\mingw\msys\1.0\include\usb.h)
- copy lib/gcc/libusb.a from the libusb package to c:\mingw\msys\1.0\lib
- start the mingw shell from programs->mingw->mingw shell
- compile the code with

gcc -o controlio controlio.c /lib/libusb.a -I/include

- connect the USB device to the computer
- start bin/inf-wizard from the libusb package
- select the connected device from the list, then create and install a driver for it
- find the executable controlio.exe under c:\mingw\msys\1.0\home\<user> where user is your user name
- check operation with the command

 controlio getport

Programming the GPIO device from python

  1. install pyusb package or download and install pyusb from http://walac.github.io/pyusb/
    yum install pyusb

    # or

    wget -O pyusb.zip https://github.com/walac/pyusb/zipball/master
    unzip pyusb.zip
    cd walac-pyusb-*
    sudo python setup.py install
  2. install the libusb library/driver as described under "Installing on the host"
  3. copy src/host/python/usbio_example.py to the host
  4. play with the example code

USB requests

The circuit is a full speed (12Mbit) vendor-specific USB device. It uses only the control endpoint 0, and is controlled by vendor-specific control requests. If you want to make your own host interface, the implemented control requests are:

command name
setup bmRequestType
setup bRequest
setup wValue
setup wLength
response
GETPORT
USB_TYPE_VENDOR, USB_ENDPOINT_IN, USB_RECIP_DEVICE
0x53
unused
8
2 bytes, I/O port states
SETPORT
USB_TYPE_VENDOR, USB_ENDPOINT_OUT, USB_RECIP_DEVICE
0x54
I/O port states <n>
0
0 bytes ACK
SETDIR
USB_TYPE_VENDOR, USB_ENDPOINT_OUT, USB_RECIP_DEVICE 0x55
I/O port directions <n>
0
0 bytes ACK
SETBIT
USB_TYPE_VENDOR, USB_ENDPOINT_OUT, USB_RECIP_DEVICE 0x56
I/O port pin selection <n>
0
0 bytes ACK
CLEARBIT
USB_TYPE_VENDOR, USB_ENDPOINT_OUT, USB_RECIP_DEVICE 0x57
I/O port pin selection <n>
0
0 bytes ACK


You can find the explanation of these USB requests (bRequest) and wValue <n> under "controlling the GPIO extender"

Planned improvements

Please contact me if you need a feature, or have an idea.

related projects

References

feedback

Please contact the author if you found an error, incomplete or missing documentation, or you have trouble making this circuit work.

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