{"id":10477,"date":"2020-04-08T12:05:29","date_gmt":"2020-04-08T15:05:29","guid":{"rendered":"http:\/\/kb.elipse.com.br\/en\/?p=10477"},"modified":"2024-02-08T10:10:19","modified_gmt":"2024-02-08T13:10:19","slug":"common-issues-faced-by-modbus-driver-multiple-slaves-with-rs-485-converter","status":"publish","type":"post","link":"https:\/\/kb.elipse.com.br\/en\/common-issues-faced-by-modbus-driver-multiple-slaves-with-rs-485-converter\/","title":{"rendered":"Common issues faced by Modbus driver: Multiple slaves with RS-485 converter."},"content":{"rendered":"<h3><strong>Question:<\/strong><\/h3>\n<p style=\"text-align: justify;\">How can you fix communication issues with Modbus and multiple slaves with a RS-485 converter? I have a Modbus Master driver (<a href=\"https:\/\/www.elipse.com.br\/en\/downloads\/?cat=48&#038;key=&#038;language=enus\" target=\"_blank\" rel=\"noopener noreferrer\">Modbus-TCP<\/a>) protocol connected to an Ethernet\/RS485 converter; the RS-485 network has two slave devices (Modbus-RTU protocol).<\/p>\n<p><a href=\"http:\/\/kb.elipse.com.br\/wp-content\/uploads\/2019\/12\/9663\/1.png\"><img loading=\"lazy\" class=\"size-full wp-image-9664 aligncenter\" src=\"http:\/\/kb.elipse.com.br\/wp-content\/uploads\/2019\/12\/9663\/1.png\" alt=\"\" width=\"462\" height=\"237\" \/><\/a><\/p>\n<p style=\"text-align: justify;\">Often times, some of the tags will fail or go into timeout, and this issue only happens when both slaves communicate simultaneously.<\/p>\n<h3 style=\"text-align: justify;\"><strong>Solution:<\/strong><\/h3>\n<p style=\"text-align: justify;\">In many cases, the\u00a0 <strong>Ethernet\/RS485<\/strong> or <strong>Serial\/RS485 <\/strong>converter will need a delay between TX\/RX\u00a0 transactions; this happens in order to be able to communicate with multiple slaves on the RS-485 network, and by default this is not the case.<\/p>\n<p style=\"text-align: justify;\">The option <em><strong>Inter-frame delay<\/strong><\/em> on Serial and Ethernet tab (<strong>IOKit<\/strong> v<strong>2.0.125<\/strong>), which sets up a waiting time between packets that are either sent to or received from IOKit in milliseconds (1000 = 1 second), can introduce this delay.<\/p>\n<p style=\"text-align: justify;\">For previous versions of the <strong>IOkit<\/strong>, when<strong> converting RS485 to Serial<\/strong> or<strong>\u00a0RS485 to Ethernet, <\/strong>you can use a Modbus\u00a0 driver parameter; this parameter is hidden in the Properties dialog and it will delay TX\/RX transactions when slaves exchange their IDs.<\/p>\n<p style=\"text-align: justify;\">To set it up, you could start the driver offline (<em><strong>Start driver OFFLINE<\/strong><\/em> option on Setup tab), and then add this script at the driver&#8217;s <em>AfterStart<\/em> event:<\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"null\">Sub Modbus1_AfterStart()\r\n\r\n' Habilita a funcao Swap Address Delay\r\nWrite -1, 0, 0, 3, Array(\"ModiconModbus.UseSwapAddressDelay\", 1)\r\n\r\n' Configura o atraso (por exemplo, 300 milisegundos)\r\nWrite -1, 0, 0, 3, Array(\"ModiconModbus.SwapAddressDelay\", 300)\r\n\r\n'Online\r\nWrite -1,0,0,4,1 \r\n\r\nEnd Sub<\/pre>\n<div>In both solutions, the necessary delay may vary according to the converter, usually between 100 to 400 milliseconds.<\/div>\n<div><\/div>\n<div>The options presented in this article could help fix the communication problems presented by multiple slaves with a RS-485 converter.<\/div>\n<div><\/div>\n<div>\n<h3>Related articles:<\/h3>\n<hr \/>\n<p>The articles below all refer to common issues faced by the Modbus driver:<\/p>\n<ul>\n<li><a href=\"https:\/\/kb.elipse.com.br\/en\/?p=10699\" target=\"_blank\" rel=\"noopener noreferrer\">Discontinuous address in the device<\/a>.<\/li>\n<li><a href=\"https:\/\/kb.elipse.com.br\/en\/?p=10711\" target=\"_blank\" rel=\"noopener noreferrer\">Protocol exception codes<\/a>.<\/li>\n<li><a href=\"https:\/\/kb.elipse.com.br\/en\/?p=10717\" target=\"_blank\" rel=\"noopener noreferrer\">Incrementing non-standard addresses<\/a>.<\/li>\n<li><a href=\"https:\/\/kb.elipse.com.br\/en\/?p=10727\" target=\"_blank\" rel=\"noopener noreferrer\">Scrambled bytes and words<\/a>.<\/li>\n<li><a href=\"https:\/\/kb.elipse.com.br\/en\/?p=10735\" target=\"_blank\" rel=\"noopener noreferrer\">Registers addresses indexation<\/a>.<\/li>\n<li><a href=\"https:\/\/kb.elipse.com.br\/en\/?p=10742\" target=\"_blank\" rel=\"noopener noreferrer\">Interpreting addresses prefixes<\/a>.<\/li>\n<\/ul>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Question: How can you fix communication issues with Modbus and multiple slaves with a RS-485 converter? I have a Modbus Master driver (Modbus-TCP) protocol connected to an Ethernet\/RS485 converter; the&hellip;<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0},"categories":[792,730],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v19.8 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Communication: Modbus master and multiple slaves via RS-485 converter.<\/title>\n<meta name=\"description\" content=\"This article illustrates how to fix the communication problem between Modbus driver and multiple slaves with a Ethernet\/RS-485 converter.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" 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