SLDongle: The Microcontroller Gift That Keeps on Giving

It must be nice to be one of [kiu]’s colleagues. Some people pass out chocolates or stress balls at work as Christmas gifts, but [kiu] made a bunch of SL dongles to introduce his colleagues to the world of microcontrollers.

The dongles are based on the ATMega88PA and work on three levels to provide something for everyone. The no-experience-necessary option is to plug it in to a USB port and admire the light show sequences. If you know enough to be dangerous, you can remotely control the LEDs from a USB host using [kiu]’s sldtool for Linux or Mac. He originally included examples that visualize CPU utilization and ultimately added a Ruby-based departure countdown for the next outbound train at the nearby station.

If you’re 1337 enough you can flash your own C or assembly code via USB. Holding down the button during power-up lets you use the dongle as a USBasp so it can be flashed with avrdude. [kiu] says the bootloader can’t be unlocked through software and is theoretically unbrickable. Stick around after the break to see the full demo.

[Thanks, kiu]

14 thoughts on “SLDongle: The Microcontroller Gift That Keeps on Giving

  1. With an on-board USB connector like this, I’ve found that adding some backing material on the reverse is preferable to tinning the pads.

    Since the GND and +5V pads are wider than the data pads, they usually have more solder on them, and since the solder forms a dome shape (surface tension), the power pads are higher than the data pads. This can lead to contact problems.

    1. Neato build!

      Good points NsN, maybe the Data pads could be widened (careful not to get them too close) or the Power pads could have some solder wicked (hmmm, that doesn’t look right in print B^) off to lower their profile.

      Other suggestions, multi-color LEDs; instead of a “Figure 8″ pattern, use a “Union Jack” layout for displaying text characters…

    2. Another thing: gold contacts + tinned contacts aren’t the best combination reliability wise. Don’t think it will make much difference for something like this but can be good to know.

      Nice board/idea otherwise! :)

    3. A couple of ways of doing this for one off PCB:

      Ask for 0.031″ scrap next time you are ordering and super glue it onto
      the back. 0.031″+0.062″=0.093″

      Use gold plated 0.025″ pins from 0.1″ pitch connector on top of the
      fingers. Tin the PCB with solder first and reheating finger such that
      the solder melts and forms a joint with the pin resting on top. Now you
      have gold plated contacts! 0.025″+0.062″=0.087″

  2. The board is 2mm thick (rather than the typical 1.6mm) and my plan was to use the pads directly. But after a couple of insertions I saw that the (cheap) plating was already wearing off, so I had to tin them.

    1. metal case? Might as well use the proper “USB Male Type A connector”. They are around $1.82 for 10 pieces free shipping from DX and others.

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