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M.S. Suryateja Jammalamadaka


I am a Graduate Research Assistant in Community Biotechnology Initiative and Molecular Machines group at MIT Media Lab

Week 9: Output Devices


For this week, I wanted to make an charplieplexing LED array which is controlled by a push button. I changed Neil's board to include the push button and a pull in resistor. I designed the board in autodesk eagle. Here is the schematic and board.




PCB milled using Roland MDX-20:


Board after soldering components:



When I tried to program the board using USBtiny, it gave me an rc=-1 error. Here are the different possibilities for the error:


1. Check that you have un-soldered the 0-resistors from the ISP board!
2. Check that you installed the right FTDI drivers (OS version and 64 bits)
3. Check that the rainbow cable is well pressed and not connected backwards!
4. Check that the FTDI cable has ground (black) connected to ground in your board
5. Check Eagle schematic and fab modules toolpath against your board for milling errors
6. Check for soldering errors and loose legs
7. Check the board with a multimeter for discontinuities.


I troubleshooted the board by crosschecking if anyone of the above is the reason for the error. I desolderd attiny44 from the board and I figured out that my eagle board is not consistent with the board I milled. Four pins of the attiny44 have continuity with a trace passing through the attiny44. Here is the image after I desoldered the attiny44 from the board.



I used a razor knife from the inventory and cut the traces to disconnect them from the trace and resoldered the attiny 44 to the board.



I needed a 5V voltage source. I didn't have 5V battery. I used an 5V FTDI cable connected to the USB port as a voltage source for the board making sure to connect Vcc and GND of FTDI to appropriate pins on the board.



I programmed the board using Neil's code to see if the LED array works, it works.

I adpated the .c code to use button as an input and LED array as output when the push button is pressed. Here is the code hello.array2.44.c and the result.

I tried to reprogarm it multiple times to get different shapes. Here is one of them. Here is the code hello.array3.44.c and the result.