sldongle (sld) provides a playful entry into the world of microcontroller development.

Ingredients: LEDs, ATMega88PA, SCT2024, LD1117, V-USB, SPI, bootloader...

I wanted to provide my collegues at work a chance to discover the world of microcontrollers and came up with the idea to gift everyone a simple developement board for Christmas.

The goals for this projects were:

  • Quick turn around (Started mid November –> Christmas)
  • Programmable through USB
  • Use AVR platform, providing a path towards Arduino
  • Offer alternative functionality for people afraid of C programming
  • Keep it cheap

A few weekends later sld was born and offers quite some functionality:

The technically challenged can plug sld into their USB port and enjoy the beauty of the assembly. The LEDs light up and cycle through different animation sequences.

The more experienced can remote control the LEDs from their USB host by piping data into sldtool (linux/mac). The inital delivery contained examples to visualize the CPU utilisation (shell for linux, C for mac), but the team quickly came up with a nifty ruby solution, counting down the remaining minutes until the next train departs at the station nearby.

Bold users wanting to get their hands dirty, can – without the need of dedicated ISP hardware – flash their own C or ASM software directly via USB. Holding the button while powering up, lets sld enumerate as USBasp, which allows the board to be flashed by avrdude or similar software. As the bootloader is locked down by fuses and can’t be unlocked through software, sld is unbrickable (until proven otherwise).

See for Bill Of Materials, Eagle/Gerber files and source code.

Merry Christmas

- All files are licensed under Creative Commons Attribution 3.0 (CC BY 3.0) -