{"id":6789,"date":"2022-03-18T12:23:58","date_gmt":"2022-03-18T04:23:58","guid":{"rendered":"https:\/\/www.modbus.cn\/?p=6789"},"modified":"2026-07-01T00:01:24","modified_gmt":"2026-06-30T16:01:24","slug":"6789","status":"publish","type":"post","link":"https:\/\/www.modbus.cn\/en\/6789.html","title":{"rendered":"libmodbus\u4e2d\u6587\u7248\u624b\u518c"},"content":{"rendered":"<h2 class=\"wp-block-heading\">\u7279\u70b9<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">libmodbus\u662f\u4e00\u4e2a\u5feb\u901f\u3001\u8de8\u5e73\u53f0\u7684Modbus\u5e93\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u63cf\u8ff0<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">libmodbus\u662f\u4e00\u4e2a\u4e0e\u4f7f\u7528Modbus\u534f\u8bae\u7684\u8bbe\u5907\u8fdb\u884c\u6570\u636e\u53d1\u9001\/\u63a5\u6536\u7684\u5e93\u3002\u8be5\u5e93\u5305\u542b\u5404\u79cd\u540e\u7aef\uff08backends\uff09\u901a\u8fc7\u4e0d\u540c\u7f51\u7edc\u8fdb\u884c\u901a\u4fe1\uff08\u4f8b\u5982\uff0cRTU\u6a21\u5f0f\u4e0b\u7684\u4e32\u53e3\u6216TCP \/ IPv6\u4e2d\u7684\u4ee5\u592a\u7f51\uff09\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">http:\/\/www.modbus.org\u7f51\u7ad9\u63d0\u4f9b\u4e86\u534f\u8bae\u89c4\u8303\u6587\u6863http:\/\/www.modbus.org\/specs.php\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">libmodbus\u63d0\u4f9b\u4e86\u8f83\u4f4e\u901a\u4fe1\u5c42\u7684\u62bd\u8c61\uff0c\u5e76\u5728\u6240\u6709\u652f\u6301\u7684\u5e73\u53f0\u4e0a\u63d0\u4f9b\u76f8\u540c\u7684API\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u672c\u6587\u6863\u4ecb\u7ecd\u4e86\u4e86libmodbus\u6982\u5ff5\uff0c\u4ecb\u7ecd\u4e86libmodbus\u5982\u4f55\u4ece\u5728\u4e0d\u540c\u7684\u786c\u4ef6\u548c\u5e73\u53f0\u4e2d\u5b9e\u73b0Modbus\u901a\u4fe1\uff0c\u5e76\u4e3alibmodbus\u5e93\u63d0\u4f9b\u7684\u51fd\u6570\u63d0\u4f9b\u4e86\u53c2\u8003\u624b\u518c\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u73af\u5883(contexts)<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">RTU\u540e\u7aef\uff08\u8fdc\u7a0b\u7ec8\u7aef\u5355\u5143\uff09\u7528\u4e8e\u4e32\u53e3\u901a\u4fe1\uff0c\u5e76\u4f7f\u7528\u7528\u4e8e\u534f\u8bae\u901a\u4fe1\u7684\u6570\u636e\u7684\u7d27\u51d1\u7684\u4e8c\u8fdb\u5236\u8868\u793a\u5f62\u5f0f\u3002RTU\u683c\u5f0f\u9075\u5faa\u547d\u4ee4\/\u6570\u636e\uff0c\u548cCRC\uff08cyclic redundancy check\u5faa\u73af\u5197\u4f59\u6821\u9a8c\uff09\u4f5c\u4e3a\u9519\u8bef\u68c0\u67e5\u673a\u5236\uff0c\u4ee5\u786e\u4fdd\u6570\u636e\u7684\u53ef\u9760\u6027\u3002Modbus RTU\u662f\u53ef\u7528\u4e8eModbus\u7684\u6700\u5e38\u7528\u7684\u5b9e\u73b0\u65b9\u5f0f\u3002Modbus RTU\u6d88\u606f\u5fc5\u987b\u8fde\u7eed\u53d1\u9001\uff0c\u4e0d\u80fd\u6709\u5b57\u7b26\u95f4\u9694\uff08\u6458\u81eaWikipedia\uff0cModbus\uff0c http:\/\/en.wikipedia.org\/wiki\/Modbus \u622a\u81f32011\u5e743\u670813\u65e5\uff0c\u683c\u6797\u5c3c\u6cbb\u65f6\u95f420:51\uff09\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Modbus RTU\u6846\u67b6\u8c03\u7528\u4e00\u4e2a\u4ece\u7ad9\uff0c\u4e00\u4e2a\u5904\u7406Modbus\u8bf7\u6c42\u7684\u8bbe\u5907\/\u670d\u52a1\u5668\uff0c\u4ee5\u53ca\u4e00\u4e2a\u53d1\u9001\u8bf7\u6c42\u7684\u5ba2\u6237\u7aef\uff08\u4e3b\u7ad9\uff09\u3002\u901a\u4fe1\u59cb\u7ec8\u7531\u4e3b\u7ad9\u670d\u52a1\u7aef\u53d1\u8d77\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8bb8\u591aModbus\u8bbe\u5907\u53ef\u4ee5\u5728\u540c\u4e00\u4e2a\u7684\u7269\u7406\u94fe\u8def\u4e0a\u8fde\u63a5\u5728\u4e00\u8d77\uff08\u603b\u7ebf\u7ed3\u6784\uff09\uff0c\u56e0\u6b64\u5728\u53d1\u9001\u6d88\u606f\u4e4b\u524d\uff0c\u5fc5\u987b\u4f7f\u7528modbus_set_slave\u8bbe\u7f6e\u4ece\u7ad9\uff08\u63a5\u6536\u8bbe\u5907 \uff09ID\u3002\u5982\u679c\u60a8\u6b63\u5728\u8fd0\u884c\u4e00\u4e2a\u4ece\u7ad9\uff0c\u5219\u5176\u4ece\u7ad9\u53f7\u5c06\u7528\u4e8e\u8fc7\u6ee4\u63a5\u6536\u7684\u6d88\u606f\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u521b\u5efamodbus RTU \u73af\u5883<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u521d\u8bd5\u5316RTU\u73af\u5883\u6307\u9488 modbus_t *modbus_new_rtu(const char *device, int baud, char parity, int data_bit, int stop_bit)<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>modbus_t *modbus_new_rtu(const char *device, int baud, char parity, int data_bit, int stop_bit);\n \n \n\/\/\u53c2\u8003\u4ee3\u7801\uff1a\nmodbus_t *ctx;\n \nctx = modbus_new_rtu(\"\/dev\/ttyUSB0\", 115200, 'N', 8, 1);\nif (ctx == NULL) {\n    fprintf(stderr, \"Unable to create the libmodbus context\\n\");\n    return -1;\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd9\u4e2a modbus_new_rtu()\u51fd\u6570\u4f1a\u751f\u6210\u5e76\u521d\u59cb\u5316\u4e00\u4e2amodbus\u7684\u7ed3\u6784\u4f53\u6765\u5728\u4e32\u884c\u7ebf\u8def\u4e2d\u4f7f\u7528RTU\u6a21\u5f0f\u8fdb\u884c\u901a\u8baf\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">device \u6307\u5b9aOS\u5904\u7406\u7684\u4e32\u884c\u7aef\u53e3\u7684\u540d\u79f0\uff0c\u6bd4\u5982 \/dev\/ttyS0 or \/dev\/ttyUSB0\uff0c\u5728windows\u7cfb\u7edf\u4e0a\uff0c\u5982\u679cCOM\u7f16\u53f7\u5927\u4e8e9\uff0c\u5fc5\u987b\u8981\u5728COM\u524d\u52a0\u4e0a\\.\\ \uff0c\u6bd4\u5982 \\\\.\\COM10.\uff0c\u53c2\u7167http:\/\/msdn.microsoft.com\/en-us\/library\/aa365247(v=vs.85).aspx<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">baud \uff1a\u6307\u5b9a\u8fde\u63a5\u7684\u6ce2\u7279\u7387\uff0c\u6bd4\u59829600, 19200, 57600, 115200\u7b49\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">parity \uff1a\u4ee3\u8868\u5947\u5076\u68c0\u9a8c\u4f4d\uff0c\u6709\u5982\u4e0b\u503c\uff1a<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">N \u65e0\u5947\u5076\u6821\u9a8c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">E \u5076\u6570\u6821\u9a8c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">O \u5947\u6570\u6821\u9a8c<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">data_bit \uff1a\u6307\u5b9a\u6570\u636e\u7684\u4f4d\u6570\uff0c\u5141\u8bb8\u503c\u6709\uff1a 5, 6, 7 ,8.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">stop_bit \uff1a\u6307\u5b9a\u505c\u6b62\u4f4d\u4f4d\u6570\uff0c\u5141\u8bb8\u503c\u67091\u548c2.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd4\u56de\uff1a\u5982\u679c\u5efa\u7acb\u6210\u529f\uff0cmodbus_new_rtu\uff08\uff09\u51fd\u6570\u5c06\u8fd4\u56de\u6307\u5411modbus_t\u7ed3\u6784\u7684\u6307\u9488\u3002 \u5426\u5219\u5b83\u5c06\u8fd4\u56deNULL\u5e76\u5c06errno\u8bbe\u7f6e\u4e3aAn invalid argument was given.\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8bbe\u7f6e\u4e32\u53e3\u6a21\u5f0f<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u83b7\u53d6\u5f53\u524d\u4e32\u53e3\u6a21\u5f0f int modbus_rtu_get_serial_mode(modbus_t *<em>ctx<\/em>);<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>int modbus_rtu_get_serial_mode (modbus_t *ctx);\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd4\u56de\uff1a\u5982\u679c\u6210\u529f, \u51fd\u6570\u5e94\u8fd4\u56de&nbsp;<code>MODBUS_RTU_RS232&nbsp;<\/code>\u6216&nbsp;<code>MODBUS_RTU_RS485<\/code>&nbsp;\u3002\u5426\u5219, \u5b83\u5c06\u8fd4\u56de-1\u5e76\u5c06errno\u8bbe\u4e3aThe current libmodbus backend is not RTU.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ea\u7528\u4e8eRTU\u73af\u5883\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8bbe\u7f6e\u4e32\u53e3\u6a21\u5f0f&nbsp;<strong>int modbus_rtu_set_serial_mode(modbus_t *<em>ctx<\/em>, int&nbsp;<em>mode<\/em>);<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>int modbus_rtu_set_serial_mode(modbus_t *ctx, int mode);<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">mode: \u586b\u5165 MODBUS_RTU_RS232 \u6216 MODBUS_RTU_RS485<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd4\u56de\u503c\uff1a\u5982\u679c\u6210\u529f, \u51fd\u6570\u5e94\u8fd4\u56de0\u3002\u5426\u5219, \u5b83\u5c06\u8fd4\u56de-1 \u5e76\u5c06 errno \u8bbe\u7f6e\u4e3a\u4e0b\u9762\u5b9a\u4e49\u7684\u503c\u4e4b\u4e00\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">EINVAL The current libmodbus backend is not RTU.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">ENOTSUP The function is not supported on your platform.\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5982\u679c\u5bf9 ioctl () \u7684\u8c03\u7528\u5931\u8d25, \u5c06\u8fd4\u56de ioctl \u7684\u9519\u8bef\u4ee3\u7801\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u5728 RTU\u73af\u5883\u4e0b \u4e2d\u83b7\u53d6\u5f53\u524dRTS\u6a21\u5f0f int modbus_rtu_get_rts(modbus_t *<em>ctx<\/em>)<\/strong>(3.1.4\u7248\u672c\u8865\u5145)<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>int modbus_rtu_get_rts (modbus_t *ctx);<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u83b7\u5f97\u5728\u5f53\u524dctx\u73af\u5883\u4e0b\u53d1\u9001\u8bf7\u6c42\u7684\u7684\u6a21\u5f0f\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd4\u56de\u503c\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">   MODBUS_RTU_RTS_NONE\n\n   MODBUS_RTU_RTS_UP\n\n   MODBUS_RTU_RTS_DOWN\n\n   -1\uff0c\u5373\u8c03\u7528\u5931\u8d25\uff0c\u5e76\u8bbe\u7f6eEINVAL\u4e3aThe libmodbus backend is not RTU.<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u5728RTU\u73af\u5883\u4e0b\u83b7\u53d6\u8bbe\u7f6eRTS\u6a21\u5f0f int modbus_rtu_set_rts(modbus_t *<em>ctx<\/em>, int&nbsp;<em>mode<\/em>)<\/strong>(3.1.4\u7248\u672c\u8865\u5145)<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>int modbus_rtu_set_rts(modbus_t *ctx, int mode);\n \n\/\/\u4f8b\u5b50\uff1a\u542f\u52a8\u6709\u6b63\u6781\u6027\u7684RTS\u6a21\u5f0f\nmodbus_t *ctx;\nuint16_t tab_reg&#91;10];\n \nctx = modbus_new_rtu(\"\/dev\/ttyS0\", 115200, 'N', 8, 1);\nmodbus_set_slave(ctx, 1);\nmodbus_rtu_set_serial_mode(ctx, MODBUS_RTU_RS485);\nmodbus_rtu_set_rts(ctx, MODBUS_RTU_RTS_UP);\n \nif (modbus_connect(ctx) == -1) {\n    fprintf(stderr, \"Connexion failed: %s\\n\", modbus_strerror(errno));\n    modbus_free(ctx);\n    return -1;\n}\n \nrc = modbus_read_registers(ctx, 0, 7, tab_reg);\nif (rc == -1) {\n    fprintf(stderr, \"%s\\n\", modbus_strerror(errno));\n    return -1;\n}\n \nmodbus_close(ctx);\nmodbus_free(ctx);<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8bbe\u7f6e\u53d1\u9001\u8bf7\u6c42\u6a21\u5f0f\u7528\u4e8e\u5728RS485\u4e32\u884c\u603b\u7ebf\u4e0a\u8fdb\u884c\u901a\u8baf\uff0c\u9ed8\u8ba4\u6a21\u5f0f\u4e3aMODBUS_RTU_RTS_NONE\uff0c\u5728\u628a\u6570\u636e\u5199\u5165\u7ebf\u8def\u4e4b\u524d\u4e0d\u4f1a\u6709\u4fe1\u53f7\u53d1\u51fa\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8981\u542f\u7528RTS \u6a21\u5f0f, \u5fc5\u987b\u4f7f\u7528 MODBUS_RTU_RTS_UP\u6216MODBUS_RTU_RTS_DOWN, \u8fd9\u4e9b\u6a21\u5f0f\u542f\u7528 RTS \u6a21\u5f0f\u5e76\u540c\u65f6\u8bbe\u7f6e\u6781\u6027\u3002\u4f7f\u7528MODBUS_RTU_RTS_UP\u65f6, \u5c06RTS \u6807\u5fd7\u4f4d\u7f6e\u4e3a\u4f7f\u80fd\u5e76\u8fdb\u884c ioctl \u8c03\u7528, \u7136\u540e\u57281\u6beb\u79d2\u7684\u5ef6\u8fdf\u540e\u5728\u603b\u7ebf\u4e0a\u5199\u5165\u6570\u636e, \u7136\u540e\u5c06 RTS \u6807\u5fd7\u4f4d\u7f6e\u4e3a\u975e\u4f7f\u80fd\u8fdb\u884c\u53e6\u4e00\u4e2a ioctl \u8c03\u7528, \u5e76\u518d\u6b21\u5ef6\u8fdf1\u6beb\u79d2\u3002MODBUS_RTU_RTS_DOWN\u6a21\u5f0f\u4e0e\u4e4b\u7c7b\u4f3c, \u4f46\u4f7f\u7528\u76f8\u53cd\u7684 RTS \u6807\u5fd7\u4f4d\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5982\u679c\u6210\u529f, \u51fd\u6570\u5e94\u8fd4\u56de0\u3002\u5426\u5219, \u5b83\u5c06\u8fd4\u56de-1 \u5e76\u5c06 errno \u8bbe\u7f6e\u4e3aThe libmodbus backend isn\u2019t RTU or the mode given in argument is invalid.\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u81ea\u5b9a\u4e49RTS\u5b9e\u73b0 int modbus_rtu_set_custom_rts(modbus_t *<em>ctx<\/em>, void (<em>set_rts<\/em>) (modbus_t&nbsp;ctx, int on))<\/strong>(3.1.4\u7248\u672c\u8865\u5145)<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>int modbus_rtu_set_custom_rts(modbus_t *ctx, void (set_rts) (modbus_t ctx, int on));\n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8bbe\u7f6e\u4f20\u8f93\u524d\u540e\u8bbe\u7f6eRST PIN\u8981\u8c03\u7528\u7684\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u8bbe\u7f6e\u4e3a\u4f7f\u7528IOCTL\u8c03\u7528\u5207\u6362RTS PIN\u7684\u5185\u90e8\u51fd\u6570\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u6ce8\u610f\uff0c\u8be5\u51fd\u6570\u9075\u5faaRTS\u6a21\u5f0f\uff0c\u5fc5\u987b\u4f7f\u7528\u503cMODBUS_RTU_RTS_UP\u6216MODBUS_RTU_RTS_DOWN\u6765\u8c03\u7528\u8be5\u51fd\u6570\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd4\u56de\uff1a\u5982\u679c\u6210\u529f, modbus_rtu_set_custom_rts ()\u51fd\u6570\u5e94\u8fd4\u56de0\u3002\u5426\u5219, \u5b83\u5c06\u8fd4\u56de-1 \u5e76\u5c06 errno \u8bbe\u7f6e\u4e3aThe libmodbus backend is not RTU.<\/p>\n<span id=\"magicpostMarker\"><\/span>","protected":false},"excerpt":{"rendered":"<p>\u7279\u70b9 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