For now, usbfs could be an alternative way: http://marc.theaimsgroup.com/?l=linux-usb-users&m=106886596603257&w=2
Good luck Jay.
Goddard James wrote:
Hello,
I have some questions about the HID driver. I've seen similar questsions posted here and other locations but never an answer.
I am writing software to talk to a USB ups. Rather than make it a standard HID Power Device, the manufacturer cobbled their old serial protocol into a custom HID device. The protocol takes and returns strings of 4-8 bytes.
Under Windoze I talk to the device by calling CreateFile on the driver and then using ReadFile and WriteFile to send and receive the strings. I append a 0 to the beginning of the data on the Write to indicate which report to use.
On the Mac I use the HIDDispatchTable call of pHIDSetReport, passing the string as the third parameter.
On Linux I can find no way to send a string to the device. Using some of the tools available I have queried the device and discovered that it has one input and one output report, each with one field of two usages. I had assumed that since the usage value is 4 bytes that I would need to munge my string into the two usages and send the string to the device. I have not been able to make this work and always get 0 back in response.
My question is, how exactly do you send a string to an HID device on Linux. I have scoured the internet and seen others ask the same question but none have ever got an answer. Any help you could provide would be extremely welcomed.
Attached it some test code and the output results.
Thanks,
James
#include <asm/types.h> #include <sys/ioctl.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <linux/hiddev.h> #include <stdio.h> #include <unistd.h>
int main()
{
int nfile = open( "/dev/usb/hid/hiddev0", O_RDONLY);
printf( "Opened file\n");
ioctl( nfile, HIDIOCINITREPORT, 0);
printf( "Initialized reports\n");
hiddev_usage_ref usage = { 0 };
usage.report_type = HID_REPORT_TYPE_OUTPUT;
usage.report_id = HID_REPORT_ID_FIRST;
usage.field_index = 0;
usage.usage_index = 0;
usage.usage_code = 0;
//usage.value = *((__s32 *)(":\x00\xFF\r"));
usage.value = *((__s32 *)("\r\xFF\x00:"));
int nret = ioctl( nfile, HIDIOCSUSAGE, &usage);
printf( "SUSAGE returned %d\n", nret);
usage.usage_index = 1;
usage.value = 0;
nret = ioctl( nfile, HIDIOCSUSAGE, &usage);
printf( "SUSAGE returned %d\n", nret);
hiddev_report_info report = { 0 };
report.report_type = HID_REPORT_TYPE_OUTPUT;
report.report_id = HID_REPORT_ID_FIRST;
report.num_fields = 1;
nret = ioctl( nfile, HIDIOCSREPORT, &report);
printf( "SREPORT returned %d\n", nret);
report.report_type = HID_REPORT_TYPE_INPUT;
report.report_id = HID_REPORT_ID_FIRST;
report.num_fields = 2;
nret = ioctl( nfile, HIDIOCGREPORT, &report);
printf( "GREPORT returned %d\n", nret);
usage.report_type = HID_REPORT_TYPE_INPUT;
usage.report_id = HID_REPORT_ID_FIRST;
usage.field_index = 0;
usage.usage_index = 0;
usage.usage_code = 0;
usage.value = 0;
nret = ioctl( nfile, HIDIOCGUSAGE, &usage);
printf( "GUSAGE returned %d with value 0x%X\n", nret, usage.value);
close( nfile);
return 0;
}
Output:
Opened file Initialized reports SUSAGE returned 0 SUSAGE returned 0 SREPORT returned 0 GREPORT returned 0 GUSAGE returned 0 with value 0x0 <-- Should be UPS result
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