Adafruit: Bicolor LED Square Pixel Matrix
Embedded Linux Class by Mark A. Yoder
Page by Alex Drane, Peter Ngo
This page details project work done while working on the 8x8 Bicolor LED Pixel Matrix from Adafruit found here: Store Link
The device still remains nonfunctional. Communication using I2C has been established and the device responds. The bottom row of the display is able to come on dimly when conditions outlined in the Making "Something Happen section.
Means of Making "Something" Visible
While we cannot currently turn on an individual pixel we were able to establish that the device was responding to I2C input. Directions:
i2cset -y 3 0x70 0x21 i2cset -y 3 0x70 0x81 i2cset -y 3 0x70 0xA1
The bottom row should be visible, barely. What you have done is turn on the devices oscillator, turn on the LED screen, and set it to INT active low control. No other combination currently makes the device do anything. Brightness control does not effect the row. We did show that we were turning the oscillator on and off by using:
i2cset 3 0x70 0x20
To turn off the row. Currently I have no explanation for why it does not work.
I am able to program the 0x00-0x0f memory address range with values that I can read back and that should control the LED matrix when the
i2cset -y 3 0x70 0xA0
Command is used. This does nothing. Brightness was checked at 0xEF and 0xE0 to make sure that brightness was not being misunderstood. This has no effect.
Setting the display to blinking (0x83, 0x85) also did nothing.
Code provided by Adafruit was for the Adrino board and using it as a guide I established that it should be possible to control the screen manually. I acquired the data sheet for the HT16k33 and that was how I was able to experiment as I did above.