{"id":1877,"date":"2016-05-29T00:05:35","date_gmt":"2016-05-28T22:05:35","guid":{"rendered":"http:\/\/www.sciencetronics.com\/greenphotons\/?p=1877"},"modified":"2025-06-16T18:37:52","modified_gmt":"2025-06-16T16:37:52","slug":"deutsch-ein-usbasp-im-neuen-gewand-2","status":"publish","type":"post","link":"https:\/\/www.sciencetronics.com\/greenphotons\/?p=1877","title":{"rendered":"An USBasp in a new design II"},"content":{"rendered":"

Most of the time I design and debug my AVR projects on solderless breadboards nowadays. And for that I have been using some different types of programmers by now: starting with the good old STK500<\/a>, to different versions of USBasp<\/a> clones from Chinese sellers on eBay<\/a>.<\/p>\n

In order to connect the programmers to the breadboard I started with loose wires, discovered a nice breadboard adapter from Sparkfun<\/a> (now retired), before I rolled out my own version<\/a> which I also use with my students.<\/p>\n

Why another design for an AVR programmer?<\/h3>\n

Starting last year it became necessary to run some projects from batteries or at 3.3 V which is not supported by all Chinese programmer clones, and also the wiring of the supply from the programming adapter to the power lines of the breadboard added to the number of wires – and sometimes it added clutter to the breadboard. <\/p>\n

Having nothing else to do (?) I decided last weekend to design my own circuit board for the USBasp, which attaches to the breadboard much like the MB102 power supply adapter available form your favorite Chinese reseller, directly connecting to the power rails and also including a 3.3 V regulator.<\/p>\n

\"MB102<\/a>
MB102 power supply adapter for breadboards.<\/figcaption><\/figure>\n

Design process<\/h3>\n

I started with some compromises:<\/p>\n

Single or double?<\/h4>\n

As usual I wanted to be able to make the circuit board using the toner transfer process<\/a> and therefore it should preferably be a single sided circuit board. But this is difficult with the pinheaders which need to be on the underside, attaching to the breadboard. While it is possible to solder them this way onto a circuit board it’s usually not a good joint. I decided to start with a design for a single-sided board.<\/p>\n

SMD or through-hole?<\/h4>\n

Most of the time I still favor through-hole design for my own projects, probably because of my big stock of through-hole parts. But I also have to acknowledge that not having to drill your own PCBs is a big advantage. When it comes to the pinheaders again, while there are SMD-versions around, I don’t trust the long-term reliability of the corresponding joints, so these would be through-hole anyway. Like the Chinese manufacturers I also went for a through-hole quartz crystal, while the rest of the board became SMD. <\/p>\n

This way the parts and traces would be on the top of the board and the pinheaders would be soldered from the correct side.<\/p>\n

Which USB contact?<\/h4>\n

The Chinese USBasp clones normally come with an USB-A contact, allowing them to be used like USB sticks. However, most of the time you might want to have your circuit at a flexible position and distance from your computer, making it necessary to use a USB A-A M\/F extension cable. From the definition of the USB standard it would make more sense to use a B-type contact.<\/p>\n

Just recently Dave Jones<\/a> was wondering why someone would still use a mini-B type contact on their gear, not the more modern micro-B. So what should I use:<\/p>\n

\"Three<\/a>
Three USB B connectors – which to choose?<\/figcaption><\/figure>\n