{"id":1136,"date":"2014-03-11T03:54:54","date_gmt":"2014-03-11T03:54:54","guid":{"rendered":"http:\/\/paulrickards.com\/?p=1136"},"modified":"2015-10-24T16:25:25","modified_gmt":"2015-10-24T20:25:25","slug":"diy-rs-232-interface-for-commodore-c64-for-under-15","status":"publish","type":"post","link":"https:\/\/biosrhythm.com\/?p=1136","title":{"rendered":"DIY RS-232 Interface for Commodore C64 for under $15"},"content":{"rendered":"<p>If you have a Commodore 64, chances are you&#8217;ll eventually need to connect a modem or other serial device to it. You&#8217;ll find that&#8217;s not quite that easy since the C64 doesn&#8217;t have a standard RS-232 serial port. What it does have is called the &#8220;user port&#8221; and it can do serial over this port but it needs to be changed from TTL levels (0 to +5v) to RS-232 levels (-15v to +15v).<\/p>\n<p>If you&#8217;ve ever attempted to purchase a VIC-1011a terminal type, SwiftLink or Turbo232 from eBay you&#8217;ll quickly find out that the price gets out of hand. Expect to pay upwards of $100 or more for these adapters.<\/p>\n<p>Luckily, there&#8217;s an inexpensive way to get a RS-232 port on your C64 and it&#8217;ll cost you less than $15. Ready?<\/p>\n<p>You&#8217;ll need these parts for the project.<\/p>\n<ul>\n<li><a href=\"https:\/\/www.jameco.com\/webapp\/wcs\/stores\/servlet\/Product_10001_10001_2157845_-1\">DFRobot RS232-TTL Module from Jameco.com<\/a> for $10<\/li>\n<li><a href=\"http:\/\/www.ebay.com\/itm\/400346642707\">User port edge connector from eBay<\/a> for $1.75<\/li>\n<li>Null modem adapter<\/li>\n<li>Connecting wire<\/li>\n<li>Soldering iron<\/li>\n<\/ul>\n<p>Connect the RS232-TTL module directly to the C64 user port edge connector using the table below.<\/p>\n<table>\n<tr>\n<th>RS232-TTL Module<\/th>\n<th>C64 User Port<\/th>\n<\/tr>\n<tr>\n<td>GND<\/td>\n<td>A &#038; N<\/td>\n<\/tr>\n<tr>\n<td>TXD<\/td>\n<td>M<\/td>\n<\/tr>\n<tr>\n<td>RXD<\/td>\n<td>B &#038; C<\/td>\n<\/tr>\n<tr>\n<td>VCC<\/td>\n<td>2<\/td>\n<\/tr>\n<\/table>\n<p><strong>Update!<\/strong> Alwyz from 1200baud suggested that connecting VCC isn&#8217;t necessary and potentially dangerous. I&#8217;ve had zero problems with mine as listed here. I&#8217;m providing this warning so you can make your own decision!<\/p>\n<p><a href=\"http:\/\/paulrickards.com\/wp-content\/uploads\/2014\/03\/IMG_1718.jpg\"><img loading=\"lazy\" src=\"http:\/\/paulrickards.com\/wp-content\/uploads\/2014\/03\/IMG_1718-840x629.jpg\" alt=\"C64 RS-232 Adapter\" width=\"646\" height=\"483\" class=\"alignnone size-large wp-image-1139\" srcset=\"https:\/\/biosrhythm.com\/wp-content\/uploads\/2014\/03\/IMG_1718-840x629.jpg 840w, https:\/\/biosrhythm.com\/wp-content\/uploads\/2014\/03\/IMG_1718-300x225.jpg 300w\" sizes=\"(max-width: 646px) 100vw, 646px\" \/><\/a><\/p>\n<p>Observe which side of the user port connector is the top (it&#8217;s the one with numbers&#8211; letters are on the bottom). It&#8217;s helpful to write on it with marker. For wire I used female jumper wire that I cut one end off. For GND and RXD you&#8217;ll need to jumper two of the pins together on the user port connector. I used a small bit of CAT5 solid core wire.<\/p>\n<p>Once you&#8217;ve got it connected, add the null modem adapter and connect your modem. You may need to also use a gender changer and\/or a 9 pin to 25 pin adapter depending on your modem.<\/p>\n<p>Fire up CCGMS, Novaterm or <a href=\"http:\/\/csdb.dk\/release\/?id=113492\">Striketerm<\/a>, set the baud rate to 2400, set the port to the user port and give it a few &#8220;AT&#8221; commands. You should see &#8220;OK&#8221; being returned. If it doesn&#8217;t, make sure you have a null modem adapter (test it on another machine to confirm) and double check your connections.<\/p>\n<p>As with any tutorial you find online, be responsible and double check my work and your work before proceeding.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>If you have a Commodore 64, chances are you&#8217;ll eventually need to connect a modem or other serial device to it. You&#8217;ll find that&#8217;s not quite that easy since the C64 doesn&#8217;t have a standard RS-232 serial port. What it does have is called the &#8220;user port&#8221; and it can do serial over this port [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[6,15],"tags":[],"_links":{"self":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/posts\/1136"}],"collection":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1136"}],"version-history":[{"count":9,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/posts\/1136\/revisions"}],"predecessor-version":[{"id":1150,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=\/wp\/v2\/posts\/1136\/revisions\/1150"}],"wp:attachment":[{"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1136"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1136"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/biosrhythm.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1136"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}