I have used kermit for connecting to serial interfaces for several years and it has always worked as expected. Even for sending a kernel image to U-Boot using the zmodem protocol (yes, it took ages, but there was no Ethernet) has worked quite well.<\/p>\n
Recently, a friend that is new to embedded Linux ask me how to connect to a serial interface, so this is a small and simple guide on how to do it.<\/p>\n
Just as an intro, a summary of what is kermit taken from the Fedora repo:<\/p>\n
C-Kermit is a combined serial and network communication software package offering a consistent, medium-independent, cross-platform approach to connection establishment, terminal sessions, file transfer and management, character-set translation, and automation of communication tasks.<\/p><\/blockquote>\n
Installation<\/strong>
\nIf you have Fedora, CentOS, SuSE or other rpm based distribution<\/p>\n\r\nyum install ckermit\r\n<\/pre>\nIf you have Debian, Mint, Ubuntu or other deb based distribution<\/p>\n
\r\napt-get install ckermit\r\n<\/pre>\nConfiguration<\/strong>
\nCreate the configuration file .kermrc<\/em> in your home directory. These parameters are normally right for most systems. I’ve used it for SH4 and ARM based devices:<\/p>\n\r\nset line \/dev\/ttyUSB0\r\nset speed 115200\r\nset carrier-watch off\r\nset handshake none\r\nset flow-control none\r\nrobust\r\nset file type bin\r\nset file name lit\r\nset rec pack 1000\r\nset send pack 1000\r\nset window 5\r\nconnect\r\n<\/pre>\nThe most important parameters here are the line<\/em> parameter that indicates the serial device and the speed<\/em> parameters that is it’s baud rate. If you have an USB-to-serial interface converter your device will be \/dev\/ttyUSBx<\/em> where x is normally 0, but it depends on how may USB-to-serial converters you have. The same happens if you have a normal serial cable, except that your device will be named \/dev\/ttySx, where x is normally 0.<\/p>\n
Permissions<\/strong>
\nAdd your user to the dialout<\/em> group in the \/etc\/group<\/em> file<\/p>\n\r\ndialout:x:18:paguilar\r\n<\/pre>\nLogout and login again. This is needed since the group to which a user belongs are assigned when the user logs in.<\/p>\n
Execution<\/strong>
\nOpen a shell and execute kermit. The output should be something like this:<\/p>\n\r\nConnecting to \/dev\/ttyUSB0, speed 115200\r\n Escape character: Ctrl-\\ (ASCII 28, FS): enabled\r\nType the escape character followed by C to get back,\r\nor followed by ? to see other options.\r\n----------------------------------------------------\r\n<\/pre>\nBy default, kermit searches the file .kermrc in your home directory. If you have several kermit config files (may be because you have several boards configured differently), you can specify it:<\/p>\n
kermit \/home\/paguilar\/.custom_kermrc<\/p>\n
If there are problems like the wrong serial interface, you may see a message like this one:<\/p>\n
\r\n?SET SPEED has no effect without prior SET LINE\r\nSorry, you must SET LINE or SET HOST first\r\nC-Kermit 9.0.302 OPEN SOURCE:, 20 Aug 2011, for Linux (64-bit)\r\n Copyright (C) 1985, 2011,\r\n Trustees of Columbia University in the City of New York.\r\nType ? or HELP for help.\r\n<\/pre>\nYou can also have this problem if there is a lock file. This error happens if you try to access the serial interface whilst another process is already using it. It can also happen if you kill a previous kermit session when it was connected to the serial interface.
\nIn these cases you have to remove the lock file and execute kermit again.<\/p>\nAssuming that everything went right and you happily used a busybox shell or similar you can disconnect from kermit by typing Ctrl-\\ + q<\/em><\/p>\n
Just to be clear, the escape control sequence is Ctrl<\/em> and backslash<\/em> at the same time, then you enter the desired character.
\nFor example, if you are in your board’s shell, for connecting to the kermit shell just type Ctrl-\\ + c<\/em>, then enter connect<\/em> to go back to your board’s shell.<\/p>\nThat’s it.<\/p>\n","protected":false},"excerpt":{"rendered":"
I have used kermit for connecting to serial interfaces for several years and it has always worked as expected. Even for sending a kernel image to U-Boot using the zmodem protocol (yes, it took ages, but there was no Ethernet) has worked quite well. Recently, a friend that is new to embedded Linux ask me\u2026 Read More »<\/a><\/span><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,45],"tags":[47,46,48],"class_list":["post-417","post","type-post","status-publish","format-standard","hentry","category-command-line-interface","category-linux","tag-kermit","tag-linux","tag-serial-interface"],"_links":{"self":[{"href":"https:\/\/paguilar.org\/index.php?rest_route=\/wp\/v2\/posts\/417","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/paguilar.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/paguilar.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/paguilar.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/paguilar.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=417"}],"version-history":[{"count":6,"href":"https:\/\/paguilar.org\/index.php?rest_route=\/wp\/v2\/posts\/417\/revisions"}],"predecessor-version":[{"id":424,"href":"https:\/\/paguilar.org\/index.php?rest_route=\/wp\/v2\/posts\/417\/revisions\/424"}],"wp:attachment":[{"href":"https:\/\/paguilar.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=417"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/paguilar.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=417"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/paguilar.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=417"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}