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POHIDAPI in two threads
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copied!<p>According to <a href="https://github.com/signal11/hidapi/issues/72" rel="nofollow">https://github.com/signal11/hidapi/issues/72</a> HIDAPI ought to be thread safe on Linux machines. However, I can't get it working at all. This is what I do:</p> <pre><code>#ifdef WIN32 #include <windows.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <pthread.h> #include <stdlib.h> #include <assert.h> #include "hidapi.h" hid_device *handle; static void *TaskCode(void *argument) { int res; //hid_device *handle; unsigned char buf[64]; // res = hid_init(); // if( res == -1 ) // { // return (void*)1; // } // // handle = hid_open(0x0911, 0x251c, NULL); // if( handle == NULL ) // { // return (void*)2; // } printf( "while 2\n"); while( 1 ) { memset( buf, 64, 0 ); res = hid_read(handle, buf, 0); if( res == -1 ) { return (void*)3; } printf( "received %d bytes\n", res); for (int i = 0; i < res; i++) printf("Byte %d: %02x ", i+1, buf[i]); //printf( "%02x ", buf[0]); fflush(stdout); } return (void*)0; } int main(int argc, char* argv[]) { int res; //hid_device *handle; unsigned char buf[65]; res = hid_init(); if( res == -1 ) { return 1; } handle = hid_open(0x0911, 0x251c, NULL); if( handle == NULL ) { return 2; } hid_set_nonblocking( handle, 0 ); pthread_t thread; int rc = pthread_create(&thread, NULL, TaskCode, NULL); printf( "while 1\n"); while(1) { int a = getchar(); if( a == 'a') { // Get Device Type (cmd 0x82). The first byte is the report number (0x0). buf[0] = 0x0; buf[1] = 0x82; res = hid_write(handle, buf, 65); if( res != -1 ) printf( "write ok, transferred %d bytes\n", res ); else { printf( "write error\n" ); char* str = hid_error(handle); printf( "error: %s\n", str ); return 1; } } else if( a== 'b') break; } void* trc; rc = pthread_join(thread, &trc); printf( "rc code: %d\n", (int)trc ); // Finalize the hidapi library res = hid_exit(); return 0; } </code></pre> <p>If I don't use the global handle, I get 'write error' every time. If I do, as in the example, formally everything works but hid_read always returns 0 bytes... Of course, if I do simple hid_write() followed by hid_read(), I'll get the correct reply to the command 0x82 as intended. I'm really lost here, am I overlooking something?</p> <p>EDIT: to clarify, zero bytes return also for everything, incl. buttons on mouse etc. So it <em>seems</em> to work but the data buffer is always zero bytes.</p>

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