Controlling the USB Relay: #
Download: #
To control the relay board, you can download relevant files here: CLICK TO DOWNLOAD.
Command Test Application: #
Filename: CommandApp_USBRelay.exe
The CommandApp_USBRelay.exe is used to control the functionality of the USB relay via the command line. To use this application, it needs to be called inside the command prompt (cmd).
The GUI application needs to be closed when using CommandApp_USBRelay.exe. Otherwise, it will not work.
To control through Command Prompt, the line is: USBRelay(serial,oc,chan)
- Serial: The serial number of the board.
- Oc: This the operation of the relay, the options are: Open or Close. Open activates the relay, Close disconnects the relay.
- Chan: This is the relay module on the board you wish to control.
Example: USBRelay(tk421,open,2)
Success Codes: #
- If the command sent to the board is successful, a code of 0 will be returned.
- If the command sent to the board is unsuccessful, a code of 1 will be returned.
Serial Number: #
To retrieve the serial number of the board, open the application: GuiApp_English.exe
The file can be found in the TestApp directory.
Directions: #
- Connect the USB Relay board to the computer
- Open GuiApp_English.exe application.
- Click the button “Find device”.
- The connected devices will be displayed In the drop-down field, and this is where you will find the serial number.
Test Application with Graphical User Interface: #
Filename: GuiApp_English.exe
The GuiApp_English.exe application is used to control the functionality of the USB relay via a graphical user interface. The GUI allows for easy use of the relay by allowing for simple button clicks to control the relay.
To control the relay via the GUI: #
- Connect the USB Relay board to the computer.
- Open the GuiApp_English.exe application.
- Click the “Find device” button.
- Connected boards will be displayed in the drop downfield.
- Select the board you wish to control, and click the “open device” button.
- The board is now selected, and can be used via the program to control it.
Using with C++: #
The download file contains a folder called “usb_relay_dll” these files are used to integrate the functionality of the USB relay in your own custom application.
The folder contains the following files:
- usb_relay_device.dll
- usb_relay_device.h
- usb_relay_device.lib
Note: the below information is from another document, and we can’t provide support in troubleshooting integration issues with your custom application.
How to use in Visual Studio: #
- Create a new C++ project.
- In the stdfax.h file add the following lines:
- #include “usb_relay_device.h”
- #pragma comment(lib, “usb_relay_device.lib”)
- Copy the usb_relay_device.dll file to the directory used for your application, such as the “Release” or “Debug” directory.
Calling the board: #
- Call usb_relay_init() to init the lib.
- Call usb_relay_device_enumerate() to retrieve the devices connected to the computer.
- Call usb_relay_device_open() to open the desired board/device.
Controlling the board: #
- Call usb_relay_device_open_one_relay_channel() to open one relay
- Call usb_relay_device_open_all_relay_channel() to open all relays
- Call usb_relay_device_close_relay_channe() to close one relay
- Call usb_relay_device_close_all_relay_channel() to close all relays
Linux: #
Find attached a link to a GitHub project for USB Relay Driver For Linux.
This is a relatively updated project and could prove to be useful for users wanting to use these modules with Linux.
https://github.com/darrylb123/usbrelay/blob/master/README.md
For historical purposes, a backup of the files and readme can be downloaded below, check the link above first for updated versions. This backup was taken on 06/12/2022.
HID API for Linux, Mac OS X, and Windows ReadMe File
THE CONTENT BELOW IS FOR HISTORICAL PURPOSES AS THE ORIGINAL WEBSITE IS NOW OFFLINE
This information origially appeared on the website: http://www.signal11.us/oss/hidapi/ which is no longer operational.
HID API for Linux, Mac OS X, and Windows #
About #
HIDAPI is a multi-platform library which allows an application to interface with USB and Bluetooth HID-Class devices on Windows, Linux, and Mac OS X. While it can be used to communicate with standard HID devices like keyboards, mice, and Joysticks, it is most useful when used with custom (Vendor-Defined) HID devices. Many devices do this in order to not require a custom driver to be written for each platform. HIDAPI is easy to integrate with the client application, just requiring a single source file to be dropped into the application. On Windows, HIDAPI can optionally be built into a DLL.
Programs which use HIDAPI are driverless, meaning they do not require the use of a custom driver for each device on each platform.
HIDAPI provides a clean and consistent interface for each platform, making it easier to develop applications which communicate with USB HID devices without having to know the details of the HID libraries and interfaces on each platform.
The HIDAPI source also provides a GUI test application which can enumerate and communicate with any HID device attached to the system. The test GUI compiles and runs on all platforms supported by HIDAPI.
What Does the API Look Like? #
The API provides an easy method to enumerate HID devices attached to the system, and easy access to the functionality of the most commonly used HID functions including transfer of Input, Output, and Feature Reports. The sample program, which communicates with a modified version of the USB Generic HID sample which is part of the Microchip Application Library (in folder “Microchip Solutions\USB Device – HID – Custom Demos\Generic HID – Firmware” when the Microchip Application Framework is installed), looks like this (with error checking removed for simplicity)
#include <stdio.h>
#include <stdlib.h>
#include "hidapi.h"
int main(int argc, char* argv[])
{
int res;
unsigned char buf[65];
#define MAX_STR 255
wchar_t wstr[MAX_STR];
hid_device *handle;
int i;
// Enumerate and print the HID devices on the system
struct hid_device_info *devs, *cur_dev;
devs = hid_enumerate(0x0, 0x0);
cur_dev = devs;
while (cur_dev) {
printf("Device Found\n type: %04hx %04hx\n path: %s\n serial_number: %ls",
cur_dev->vendor_id, cur_dev->product_id, cur_dev->path, cur_dev->serial_number);
printf("\n");
printf(" Manufacturer: %ls\n", cur_dev->manufacturer_string);
printf(" Product: %ls\n", cur_dev->product_string);
printf("\n");
cur_dev = cur_dev->next;
}
hid_free_enumeration(devs);
// Open the device using the VID, PID,
// and optionally the Serial number.
handle = hid_open(0x4d8, 0x3f, NULL);
// Read the Manufacturer String
res = hid_get_manufacturer_string(handle, wstr, MAX_STR);
printf("Manufacturer String: %ls\n", wstr);
// Read the Product String
res = hid_get_product_string(handle, wstr, MAX_STR);
printf("Product String: %ls\n", wstr);
// Read the Serial Number String
res = hid_get_serial_number_string(handle, wstr, MAX_STR);
printf("Serial Number String: %ls", wstr);
printf("\n");
// Send a Feature Report to the device
buf[0] = 0x2; // First byte is report number
buf[1] = 0xa0;
buf[2] = 0x0a;
res = hid_send_feature_report(handle, buf, 17);
// Read a Feature Report from the device
buf[0] = 0x2;
res = hid_get_feature_report(handle, buf, sizeof(buf));
// Print out the returned buffer.
printf("Feature Report\n ");
for (i = 0; i < res; i++)
printf("%02hhx ", buf[i]);
printf("\n");
// Set the hid_read() function to be non-blocking.
hid_set_nonblocking(handle, 1);
// Send an Output report to toggle the LED (cmd 0x80)
buf[0] = 1; // First byte is report number
buf[1] = 0x80;
res = hid_write(handle, buf, 65);
// Send an Output report to request the state (cmd 0x81)
buf[1] = 0x81;
hid_write(handle, buf, 65);
// Read requested state
res = hid_read(handle, buf, 65);
if (res < 0)
printf("Unable to read()\n");
// Print out the returned buffer.
for (i = 0; i < res; i++)
printf("buf[%d]: %d\n", i, buf[i]);
return 0;
}License #
HIDAPI may be used by one of three licenses as outlined in LICENSE.txt. These licenses are:
- GPL v3 (see LICENSE-gpl3.txt),
- BSD (see LICENSE-bsd.txt),
- The more liberal original HIDAPI license (see LICENSE-orig.txt).
The user of HIDAPI (the developer who uses HIDAPI in their code) can choose to use HIDAPI under any of
the three licenses at their discretion. For example:
- An author of GPL software would likely use HIDAPI under the terms of the GPL.
- An author of commercial, closed-source software would likely use HIDAPI under the terms of either the BSD-style license or the original HIDAPI license.
The idea is to make HIDAPI accessable to as many users as possible for both open- and closed-source applications, and to give users the flexibility to link with the code in any way they see fit.
Download #
HIDAPI can be downloaded from GitHub. A zip file is available from the Download Page. To get the latest trunk revision (if you have git installed, run the following:
git clone git://github.com/signal11/hidapi.git
Build Instructions #
Windows: #
Build the .sln file in the windows/ directory using Visual Studio.
Linux: #
Change to the linux/ directory and run make.
Mac OS X: #
Change to the mac/ directory and run make.
To build the Test GUI: #
- On Windows, build the .sln file in the hidtest/ directory. Make sure to first set up the externals (Fox Toolkit) as described in README.txt.
- On Linux and Mac, run make from the hidtest/ directory. Make sure to first install fox-toolkit as described in README.txt
Hidapi API Functions #
| int HID_API_EXPORT HID_API_CALL | hid_init (void) Initialize the HIDAPI library. |
| int HID_API_EXPORT HID_API_CALL | hid_exit (void) Finalize the HIDAPI library. |
| struct hid_device_info HID_API_EXPORT *HID_API_CALL | hid_enumerate (unsigned short vendor_id, unsigned short product_id) Enumerate the HID Devices. |
| void HID_API_EXPORT HID_API_CALL | hid_free_enumeration (struct hid_device_info *devs) Free an enumeration Linked List. |
| HID_API_EXPORT hid_device *HID_API_CALL | hid_open (unsigned short vendor_id, unsigned short product_id, const wchar_t *serial_number) Open a HID device using a Vendor ID (VID), Product ID (PID) and optionally a serial number. |
| HID_API_EXPORT hid_device *HID_API_CALL | hid_open_path (const char *path) Open a HID device by its path name. |
| int HID_API_EXPORT HID_API_CALL | hid_write (hid_device *device, const unsigned char *data, size_t length) Write an Output report to a HID device. |
| int HID_API_EXPORT HID_API_CALL | hid_read_timeout (hid_device *dev, unsigned char *data, size_t length, int milliseconds) Read an Input report from a HID device with timeout. |
| int HID_API_EXPORT HID_API_CALL | hid_read (hid_device *device, unsigned char *data, size_t length) Read an Input report from a HID device. |
| int HID_API_EXPORT HID_API_CALL | hid_set_nonblocking (hid_device *device, int nonblock) Set the device handle to be non-blocking. |
| int HID_API_EXPORT HID_API_CALL | hid_send_feature_report (hid_device *device, const unsigned char *data, size_t length) Send a Feature report to the device. |
| int HID_API_EXPORT HID_API_CALL | hid_get_feature_report (hid_device *device, unsigned char *data, size_t length) Get a feature report from a HID device. |
| void HID_API_EXPORT HID_API_CALL | hid_close (hid_device *device) Close a HID device. |
| int HID_API_EXPORT_CALL | hid_get_manufacturer_string (hid_device *device, wchar_t *string, size_t maxlen) Get The Manufacturer String from a HID device. |
| int HID_API_EXPORT_CALL | hid_get_product_string (hid_device *device, wchar_t *string, size_t maxlen) Get The Product String from a HID device. |
| int HID_API_EXPORT_CALL | hid_get_serial_number_string (hid_device *device, wchar_t *string, size_t maxlen) Get The Serial Number String from a HID device. |
| int HID_API_EXPORT_CALL | hid_get_indexed_string (hid_device *device, int string_index, wchar_t *string, size_t maxlen) Get a string from a HID device, based on its string index. |
| HID_API_EXPORT const wchar_t *HID_API_CALL | hid_error (hid_device *device) Get a string describing the last error which occurred. |
Function Documentation #
void HID_API_EXPORT HID_API_CALL hid_close ( hid_device * device )
Close a HID device.
Parameters:
device A device handle returned from hid_open().
struct hid_device_info HID_API_EXPORT* HID_API_CALL hid_enumerate ( unsigned short vendor_id,
unsigned short product_id ) [read]
Enumerate the HID Devices.
This function returns a linked list of all the HID devices attached to the system which match vendor_id and product_id. If vendor_id is set to 0 then any vendor matches. If product_id is set to 0 then any product matches. If vendor_id and product_id are both set to 0, then all HID devices will be returned.
Parameters:
vendor_id The Vendor ID (VID) of the types of device to open.
product_id The Product ID (PID) of the types of device to open.
Returns:
This function returns a pointer to a linked list of type struct hid_device, containing information about the HID devices attached to the system, or NULL in the case of failure. Free this linked list by calling hid_free_enumeration().
HID_API_EXPORT const wchar_t* HID_API_CALL hid_error ( hid_device * device )
Get a string describing the last error which occurred.
Parameters:
device A device handle returned from hid_open().
Returns:
This function returns a string containing the last error which occurred or NULL if none has occurred.
int HID_API_EXPORT HID_API_CALL hid_exit ( void )
Finalize the HIDAPI library.
This function frees all of the static data associated with HIDAPI. It should be called at the end of execution to avoid memory leaks.
Returns:
This function returns 0 on success and -1 on error.
void HID_API_EXPORT HID_API_CALL hid_free_enumeration ( struct hid_device_info * devs )
Free an enumeration Linked List.
This function frees a linked list created by hid_enumerate().
Parameters:
devs Pointer to a list of struct_device returned from hid_enumerate().
int HID_API_EXPORT HID_API_CALL hid_get_feature_report ( hid_device * device,unsigned char * data,
size_t length )
Get a feature report from a HID device.
Set the first byte of data[] to the Report ID of the report to be read. Make sure to allow space for this extra byte in data[]. Upon return, the first byte will still contain the Report ID, and the report data will start in data[1].
Parameters:
device A device handle returned from hid_open().
data A buffer to put the read data into, including the Report ID. Set the first byte of data[] to the Report ID of the report to be read, or set it to zero if your device does not use numbered reports.
length The number of bytes to read, including an extra byte for the report ID. The buffer can be longer than the actual report.
Returns:
This function returns the number of bytes read plus one for the report ID (which is still in the first byte), or -1 on error.
int HID_API_EXPORT_CALL hid_get_indexed_string ( hid_device * device, int string_index, wchar_t * string, size_t maxlen )
Get a string from a HID device, based on its string index.
Parameters:
device A device handle returned from hid_open().
string_index The index of the string to get.
string A wide string buffer to put the data into.
maxlen The length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT_CALL hid_get_manufacturer_string ( hid_device * device, wchar_t * string, size_t maxlen )
Get The Manufacturer String from a HID device.
Parameters:
device A device handle returned from hid_open().
string A wide string buffer to put the data into.
maxlen The length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT_CALL hid_get_product_string ( hid_device * device, wchar_t * string, size_t maxlen )
Get The Product String from a HID device.
Parameters:
device A device handle returned from hid_open().
string A wide string buffer to put the data into.
maxlen The length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT_CALL hid_get_serial_number_string ( hid_device * device, wchar_t * string, size_t maxlen )
Get The Serial Number String from a HID device.
Parameters:
device A device handle returned from hid_open().
string A wide string buffer to put the data into.
maxlen The length of the buffer in multiples of wchar_t.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT HID_API_CALL hid_init ( void )
Initialize the HIDAPI library.
This function initializes the HIDAPI library. Calling it is not strictly necessary, as it will be called automatically by hid_enumerate() and any of the hid_open_*() functions if it is needed. This function should be called at the beginning of execution however, if there is a chance of HIDAPI handles being opened by different threads simultaneously.
Returns:
This function returns 0 on success and -1 on error.
HID_API_EXPORT hid_device* HID_API_CALL hid_open ( unsigned short vendor_id, unsigned short product_id, const wchar_t * serial_number )
Open a HID device using a Vendor ID (VID), Product ID (PID) and optionally a serial number.
If serial_number is NULL, the first device with the specified VID and PID is opened.
Parameters:
vendor_id The Vendor ID (VID) of the device to open.
product_id The Product ID (PID) of the device to open.
serial_number The Serial Number of the device to open (Optionally NULL).
Returns:
This function returns a pointer to a hid_device object on success or NULL on failure.
HID_API_EXPORT hid_device* HID_API_CALL hid_open_path ( const char * path )
Open a HID device by its path name.
The path name be determined by calling hid_enumerate(), or a platform-specific path name can be used (eg: /dev/hidraw0 on Linux).
Parameters:
path The path name of the device to open
Returns:
This function returns a pointer to a hid_device object on success or NULL on failure.
int HID_API_EXPORT HID_API_CALL hid_read ( hid_device * device, unsigned char * data, size_t length )
Read an Input report from a HID device.
Input reports are returned to the host through the INTERRUPT IN endpoint. The first byte will contain the Report number if the device uses numbered reports.
Parameters:
device A device handle returned from hid_open().
data A buffer to put the read data into.
length The number of bytes to read. For devices with multiple reports, make sure to read an extra byte for the report number.
Returns:
This function returns the actual number of bytes read and -1 on error. If no packet was available to be read and the handle is in non-blocking mode, this function returns 0.
int HID_API_EXPORT HID_API_CALL hid_read_timeout ( hid_device * dev, unsigned char * data, size_t length, int milliseconds )
Read an Input report from a HID device with timeout.
Input reports are returned to the host through the INTERRUPT IN endpoint. The first byte will contain the Report number if the device uses numbered reports.
Parameters:
device A device handle returned from hid_open().
data A buffer to put the read data into.
length The number of bytes to read. For devices with multiple reports, make sure to read an extra byte for the report number.
milliseconds timeout in milliseconds or -1 for blocking wait.
Returns:
This function returns the actual number of bytes read and -1 on error. If no packet was available to be read within the timeout period, this function returns 0.
int HID_API_EXPORT HID_API_CALL hid_send_feature_report ( hid_device * device, const unsigned char * data, size_t length )
Send a Feature report to the device.
Feature reports are sent over the Control endpoint as a Set_Report transfer. The first byte of data[] must contain the Report ID. For devices which only support a single report, this must be set to 0x0. The remaining bytes contain the report data. Since the Report ID is mandatory, calls to hid_send_feature_report() will always contain one more byte than the report contains. For example, if a hid report is 16 bytes long, 17 bytes must be passed to hid_send_feature_report(): the Report ID (or 0x0, for devices which do not use numbered reports), followed by the report data (16 bytes). In this example, the length passed in would be 17.
Parameters:
device A device handle returned from hid_open().
data The data to send, including the report number as the first byte.
length The length in bytes of the data to send, including the report number.
Returns:
This function returns the actual number of bytes written and -1 on error.
int HID_API_EXPORT HID_API_CALL hid_set_nonblocking ( hid_device * device, int nonblock )
Set the device handle to be non-blocking.
In non-blocking mode calls to hid_read() will return immediately with a value of 0 if there is no data to be read. In blocking mode, hid_read() will wait (block) until there is data to read before returning.
Nonblocking can be turned on and off at any time.
Parameters:
device A device handle returned from hid_open().
nonblock enable or not the nonblocking reads
1 to enable nonblocking
0 to disable nonblocking.
Returns:
This function returns 0 on success and -1 on error.
int HID_API_EXPORT HID_API_CALL hid_write ( hid_device * device, const unsigned char * data, size_t length )
Write an Output report to a HID device.
The first byte of data[] must contain the Report ID. For devices which only support a single report, this must be set to 0x0. The remaining bytes contain the report data. Since the Report ID is mandatory, calls to hid_write() will always contain one more byte than the report contains. For example, if a hid report is 16 bytes long, 17 bytes must be passed to hid_write(), the Report ID (or 0x0, for devices with a single report), followed by the report data (16 bytes). In this example, the length passed in would be 17.
hid_write() will send the data on the first OUT endpoint, if one exists. If it does not, it will send the data through the Control Endpoint (Endpoint 0).
Parameters:
device A device handle returned from hid_open().
data The data to send, including the report number as the first byte.
length The length in bytes of the data to send.
Returns:
This function returns the actual number of bytes written and -1 on error.
